Showing papers in "Clinical Chemistry in 2016"

Recombinase Polymerase Amplification for Diagnostic Applications

Abstract: BACKGROUND: First introduced in 2006, recombinase polymerase amplification (RPA) has stirred great interest, as evidenced by 75 publications as of October 2015, with 56 of them just in the last 2 years. The widespread adoption of this isothermal molecular tool in many diagnostic fields represents an affordable (approximately 4.3 USD per test), simple (few and easy hands-on steps), fast (results within 5–20 min), and sensitive (single target copy number detected) method for the identification of pathogens and the detection of single nucleotide polymorphisms in human cancers and genetically modified organisms. CONTENT: This review summarizes the current knowledge on RPA. The molecular diagnostics of various RNA/DNA pathogens is discussed while highlighting recent applications in clinical settings with focus on point-of-care (POC) bioassays and on automated fluidic platforms. The strengths and limitations of this isothermal method are also addressed. SUMMARY: RPA is becoming a molecular tool of choice for the rapid, specific, and cost-effective identification of pathogens. Owing to minimal sample-preparation requirements, low operation temperature (25–42 °C), and commercial availability of freeze-dried reagents, this method has been applied outside laboratory settings, in remote areas, and interestingly, onboard automated sample-to-answer microfluidic devices. RPA is undoubtedly a promising isothermal molecular technique for clinical microbiology laboratories and emergence response in clinical settings.

Thrombin Generation Assay and Its Application in the Clinical Laboratory

Abstract: BACKGROUND: A gap exists between in vivo and ex vivo coagulation when investigated by use of the coagulation tests prothrombin time (PT) and activated partial thromboplastin time (APTT). The thrombin generation assay (TGA) has been developed to fill this gap. CONTENT: TGA evaluates thrombin generation (resulting from the action of the procoagulant driver) and decay (resulting from the action of the anticoagulant driver), thus assessing the balance between the two. Coagulation of the test plasma (platelet poor or platelet rich) is activated by small amounts of tissue factor and phospholipids, and the reaction of thrombin generation is continuously monitored by means of a thrombin-specific fluorogenic substrate. Among the parameters derived from the thrombin-generation curve, the most important is the endogenous thrombin potential, defined as the net amount of thrombin that test plasmas can generate on the basis of the relative strength of the pro- and anticoagulant drivers. TGA is therefore the candidate assay to investigate hypo- or hypercoagulability. SUMMARY: From my analysis of the literature, I draw the following conclusions. There is strong evidence that TGA is helpful to elucidate coagulation mechanisms in various clinical conditions that until recently were poorly understood (chronic liver disease; diabetes; inflammatory bowel disease, myeloproliferative neoplasms, nonalcoholic fatty liver disease). TGA is a promising laboratory tool for investigating hemorrhagic coagulopathies and monitoring replacement therapy in hemophiliacs, predicting the risk of recurrent venous thromboembolism after a first event, and monitoring patients on parenteral or oral anticoagulants. These applications require clinical trials in which TGA results are combined with specific clinical end points.

Plasma Branched-Chain Amino Acids and Incident Cardiovascular Disease in the PREDIMED Trial

Abstract: BACKGROUND: The role of branched-chain amino acids (BCAAs) in cardiovascular disease (CVD) remains poorly understood. We hypothesized that baseline BCAA concentrations predict future risk of CVD and that a Mediterranean diet (MedDiet) intervention may counteract this effect. METHODS: We developed a case-cohort study within the Prevencion con Dieta Mediterranea (PREDIMED), with 226 incident CVD cases and 744 noncases. We used LC-MS/MS to measure plasma BCAAs (leucine, isoleucine, and valine), both at baseline and after 1 year of follow-up. The primary outcome was a composite of incident stroke, myocardial infarction, or cardiovascular death. RESULTS: After adjustment for potential confounders, baseline leucine and isoleucine concentrations were associated with higher CVD risk: the hazard ratios (HRs) for the highest vs lowest quartile were 1.70 (95% CI, 1.05–2.76) and 2.09 (1.27–3.44), respectively. Stronger associations were found for stroke. For both CVD and stroke, we found higher HRs across successive quartiles of BCAAs in the control group than in the MedDiet groups. With stroke as the outcome, a significant interaction ( P = 0.009) between baseline BCAA score and intervention with MedDiet was observed. No significant effect of the intervention on 1-year changes in BCAAs or any association between 1-year changes in BCAAs and CVD were observed. CONCLUSIONS: Higher concentrations of baseline BCAAs were associated with increased risk of CVD, especially stroke, in a high cardiovascular risk population. A Mediterranean-style diet had a negligible effect on 1-year changes in BCAAs, but it may counteract the harmful effects of BCAAs on stroke.

Circulating Tumor Cells: A Review of Non–EpCAM-Based Approaches for Cell Enrichment and Isolation

Abstract: Background: Circulating tumor cells (CTCs) are biomarkers for non-invasively measuring the evolution of tumor genotypes during treatment and disease progression. Recent technical progress has made it possible to detect and characterize CTCs at the single-cell level in blood. Content: Most current methods are based on epithelial cell adhesion molecule (EpCAM) detection, but numerous studies have demonstrated that EpCAM is not a universal marker for CTC detection since it fails to detect both carcinoma cells that undergo epithelial-mesenchymal transition (EMT), and CTCs of mesenchymal origin. Moreover, EpCAM expression has been found in patients with benign diseases. A large proportion of the current studies and reviews about CTCs describe EpCAM based methods, but there are evidences that not all tumor cells can be detected using this marker. Here we describe the most recent EpCAM-independent methods for enriching, isolating and characterizing CTCs, based on physical and biological characteristics, and point out their main advantages and disadvantages. Summary: CTCs offer an opportunity to obtain key biological information required for the development of personalized medicine. However there is no universal marker of these cells. To strengthen the clinical utility of CTCs, it is important to improve existing technologies and develop new, non-EpCAM based systems to enrich and isolate CTCs.

Recommendations for the Generation, Quantification, Storage, and Handling of Peptides Used for Mass Spectrometry–Based Assays

Abstract: BACKGROUND: For many years, basic and clinical researchers have taken advantage of the analytical sensitivity and specificity afforded by mass spectrometry in the measurement of proteins. Clinical laboratories are now beginning to deploy these work flows as well. For assays that use proteolysis to generate peptides for protein quantification and characterization, synthetic stable isotope–labeled internal standard peptides are of central importance. No general recommendations are currently available surrounding the use of peptides in protein mass spectrometric assays. CONTENT: The Clinical Proteomic Tumor Analysis Consortium of the National Cancer Institute has collaborated with clinical laboratorians, peptide manufacturers, metrologists, representatives of the pharmaceutical industry, and other professionals to develop a consensus set of recommendations for peptide procurement, characterization, storage, and handling, as well as approaches to the interpretation of the data generated by mass spectrometric protein assays. Additionally, the importance of carefully characterized reference materials—in particular, peptide standards for the improved concordance of amino acid analysis methods across the industry—is highlighted. The alignment of practices around the use of peptides and the transparency of sample preparation protocols should allow for the harmonization of peptide and protein quantification in research and clinical care.

Ambient Ionization Mass Spectrometry for Point-of-Care Diagnostics and Other Clinical Measurements

Abstract: BACKGROUND: One driving motivation in the development of point-of-care (POC) diagnostics is to conveniently and immediately provide information upon which healthcare decisions can be based, while the patient is on site. Ambient ionization mass spectrometry (MS) allows direct chemical analysis of unmodified and complex biological samples. This suite of ionization techniques was introduced a decade ago and now includes a number of techniques, all seeking to minimize or eliminate sample preparation. Such approaches provide new opportunities for POC diagnostics and rapid measurements of exogenous and endogenous molecules (e.g., drugs, proteins, hormones) in small volumes of biological samples, especially when coupled with miniature mass spectrometers. CONTENT: Ambient MS-based techniques are applied in diverse fields such as forensics, pharmaceutical development, reaction monitoring, and food analysis. Clinical applications of ambient MS are at an early stage but show promise for POC diagnostics. This review provides a brief overview of various ambient ionization techniques providing background, examples of applications, and the current state of translation to clinical practice. The primary focus is on paper spray (PS) ionization, which allows quantification of analytes in complex biofluids. Current developments in the miniaturization of mass spectrometers are discussed. SUMMARY: Ambient ionization MS is an emerging technology in analytical and clinical chemistry. With appropriate MS instrumentation and user-friendly interfaces for automated analysis, ambient ionization techniques can provide quantitative POC measurements. Most significantly, the implementation of PS could improve the quality and lower the cost of POC testing in a variety of clinical settings.

Systematic Evaluation of Sanger Validation of Next-Generation Sequencing Variants

Abstract: BACKGROUND: Next-generation sequencing (NGS) data are used for both clinical care and clinical research. DNA sequence variants identified using NGS are often returned to patients/participants as part of clinical or research protocols. The current standard of care is to validate NGS variants using Sanger sequencing, which is costly and time-consuming. METHODS: We performed a large-scale, systematic evaluation of Sanger-based validation of NGS variants using data from the ClinSeq® project. We first used NGS data from 19 genes in 5 participants, comparing them to high-throughput Sanger sequencing results on the same samples, and found no discrepancies among 234 NGS variants. We then compared NGS variants in 5 genes from 684 participants against data from Sanger sequencing. RESULTS: Of over 5800 NGS-derived variants, 19 were not validated by Sanger data. Using newly designed sequencing primers, Sanger sequencing confirmed 17 of the NGS variants, and the remaining 2 variants had low quality scores from exome sequencing. Overall, we measured a validation rate of 99.965% for NGS variants using Sanger sequencing, which was higher than many existing medical tests that do not necessitate orthogonal validation. CONCLUSIONS: A single round of Sanger sequencing is more likely to incorrectly refute a true-positive variant from NGS than to correctly identify a false-positive variant from NGS. Validation of NGS-derived variants using Sanger sequencing has limited utility, and best practice standards should not include routine orthogonal Sanger validation of NGS variants.

Fasting Is Not Routinely Required for Determination of a Lipid Profile: Clinical and Laboratory Implications Including Flagging at Desirable Concentration Cutpoints-A Joint Consensus Statement from the European Atherosclerosis Society and European Federation of Clinical Chemistry and Laboratory Medicine.

Abstract: AIMS: To critically evaluate the clinical implications of the use of non-fasting rather than fasting lipid profiles and to provide guidance for the laboratory reporting of abnormal non-fasting or fasting lipid profiles. METHODS AND RESULTS: Extensive observational data, in which random non-fasting lipid profiles have been compared with those determined under fasting conditions, indicate that the maximal mean changes at 1–6 h after habitual meals are not clinically significant [+0.3 mmol/L (26 mg/dL) for triglycerides; −0.2 mmol/L (8 mg/dL) for total cholesterol; −0.2 mmol/L (8 mg/dL) for LDL cholesterol; +0.2 mmol/L (8 mg/dL) for calculated remnant cholesterol; −0.2 mmol/L (8 mg/dL) for calculated non-HDL cholesterol]; concentrations of HDL cholesterol, apolipoprotein A1, apolipoprotein B, and lipoprotein(a) are not affected by fasting/non-fasting status. In addition, non-fasting and fasting concentrations vary similarly over time and are comparable in the prediction of cardiovascular disease. To improve patient compliance with lipid testing, we therefore recommend the routine use of non-fasting lipid profiles, whereas fasting sampling may be considered when non-fasting triglycerides are >5 mmol/L (440 mg/dL). For non-fasting samples, laboratory reports should flag abnormal concentrations as triglycerides ≥2 mmol/L (175 mg/dL), total cholesterol ≥5 mmol/L (190 mg/dL), LDL cholesterol ≥3 mmol/L (115 mg/dL), calculated remnant cholesterol ≥0.9 mmol/L (35 mg/dL), calculated non-HDL cholesterol ≥3.9 mmol/L (150 mg/dL), HDL cholesterol ≤1 mmol/L (40 mg/dL), apolipoprotein A1 ≤1.25 g/L (125 mg/dL), apolipoprotein B ≥1.0 g/L (100 mg/dL), and lipoprotein(a) ≥50 mg/dL (80th percentile); for fasting samples, abnormal concentrations correspond to triglycerides ≥1.7 mmol/L (150 mg/dL). Life-threatening concentrations require separate referral for the risk of pancreatitis when triglycerides are >10 mmol/L (880 mg/dL), for homozygous familial hypercholesterolemia when LDL cholesterol is >13 mmol/L (500 mg/dL), for heterozygous familial hypercholesterolemia when LDL cholesterol is >5 mmol/L (190 mg/dL), and for very high cardiovascular risk when lipoprotein(a) >150 mg/dL (99th percentile). CONCLUSIONS: We recommend that non-fasting blood samples be routinely used for the assessment of plasma lipid profiles. Laboratory reports should flag abnormal values on the basis of desirable concentration cutpoints. Non-fasting and fasting measurements should be complementary but not mutually exclusive.

Ambient Ionization Mass Spectrometry for Cancer Diagnosis and Surgical Margin Evaluation

Abstract: BACKGROUND: There is a clinical need for new technologies that would enable rapid disease diagnosis based on diagnostic molecular signatures. Ambient ionization mass spectrometry has revolutionized the means by which molecular information can be obtained from tissue samples in real time and with minimal sample pretreatment. New developments in ambient ionization techniques applied to clinical research suggest that ambient ionization mass spectrometry will soon become a routine medical tool for tissue diagnosis. CONTENT: This review summarizes the main developments in ambient ionization techniques applied to tissue analysis, with focus on desorption electrospray ionization mass spectrometry, probe electrospray ionization, touch spray, and rapid evaporative ionization mass spectrometry. We describe their applications to human cancer research and surgical margin evaluation, highlighting integrated approaches tested for ex vivo and in vivo human cancer tissue analysis. We also discuss the challenges for clinical implementation of these tools and offer perspectives on the future of the field. SUMMARY: A variety of studies have showcased the value of ambient ionization mass spectrometry for rapid and accurate cancer diagnosis. Small molecules have been identified as potential diagnostic biomarkers, including metabolites, fatty acids, and glycerophospholipids. Statistical analysis allows tissue discrimination with high accuracy rates (>95%) being common. This young field has challenges to overcome before it is ready to be broadly accepted as a medical tool for cancer diagnosis. Growing research in new, integrated ambient ionization mass spectrometry technologies and the ongoing improvements in the existing tools make this field very promising for future translation into the clinic.

Effective Use of Mass Spectrometry in the Clinical Laboratory

Abstract: Background: Historically the success of mass spectrometry in the clinical laboratory has focused on drugs of abuse confirmations, newborn screening, and steroid analysis. Clinical applications of mass spectrometry continue to expand, and mass spectrometry is now being used in almost all areas of laboratory medicine. Content: A brief background of the evolution of mass spectrometry in the clinical laboratory is provided with a discussion of future applications. Prominent examples of mass spectrometry are covered to illustrate how it has improved the practice of medicine and enabled physicians to provide better patient care. With increasing economic pressures and decreasing laboratory test reimbursement, mass spectrometry testing has been shown to provide cost-effective solutions. In addition to pointing out the numerous benefits, the challenges of implementing mass spectrometry in the clinical laboratory are also covered. Summary: Mass spectrometry continues to play a prominent role in the field of laboratory medicine. The advancement of this technology along with the development of new applications will only accelerate the incorporation of mass spectrometry into more areas of medicine.

Is the $1000 Genome as Near as We Think? A Cost Analysis of Next-Generation Sequencing.

Abstract: BACKGROUND: The substantial technological advancements in next-generation sequencing (NGS), combined with dropping costs, have allowed for a swift diffusion of NGS applications in clinical settings. Although several commercial parties report to have broken the $1000 barrier for sequencing an entire human genome, a valid cost overview for NGS is currently lacking. This study provides a complete, transparent and up-to-date overview of the total costs of different NGS applications. METHODS: Cost calculations for targeted gene panels (TGP), whole exome sequencing (WES) and whole genome sequencing (WGS) were based on the Illumina NextSeq500, HiSeq4000, and HiSeqX5 platforms, respectively. To anticipate future developments, sensitivity analyses are performed. RESULTS: Per-sample costs were €1669 for WGS, € 792 for WES and €333 for TGP. To reach the coveted $1000 genome, not only is the long-term and efficient use of the sequencing equipment needed, but also large reductions in capital costs and especially consumable costs are also required. CONCLUSIONS: WES and TGP are considerably lower-cost alternatives to WGS. However, this does not imply that these NGS approaches should be preferred in clinical practice, since this should be based on the tradeoff between costs and the expected clinical utility of the approach chosen. The results of the present study contribute to the evaluation of such tradeoffs.

Free and Glucuronide Whole Blood Cannabinoids' Pharmacokinetics after Controlled Smoked, Vaporized, and Oral Cannabis Administration in Frequent and Occasional Cannabis Users: Identification of Recent Cannabis Intake.

Abstract: BACKGROUND: There is increasing interest in markers of recent cannabis use because following frequent cannabis intake, Δ9-tetrahydrocannabinol (THC) may be detected in blood for up to 30 days. The minor cannabinoids cannabidiol, cannabinol (CBN), and THC-glucuronide were previously detected for ≤2.1 h in frequent and occasional smokers9 blood after cannabis smoking. Cannabigerol (CBG), Δ9-tetrahydrocannabivarin (THCV), and 11-nor-9-carboxy-THCV might also be recent use markers, but their blood pharmacokinetics have not been investigated. Additionally, while smoking is the most common administration route, vaporization and edibles are frequently used. METHODS: We characterized blood pharmacokinetics of THC, its phase I and phase II glucuronide metabolites, and minor cannabinoids in occasional and frequent cannabis smokers for 54 (occasional) and 72 (frequent) hours after controlled smoked, vaporized, and oral cannabis administration. RESULTS: Few differences were observed between smoked and vaporized blood cannabinoid pharmacokinetics, while significantly greater 11-nor-9-carboxy-THC (THCCOOH) and THCCOOH-glucuronide concentrations occurred following oral cannabis. CBG and CBN were frequently identified after inhalation routes with short detection windows, but not detected following oral dosing. Implementation of a combined THC ≥5 μg/L plus THCCOOH/11-hydroxy-THC ratio CONCLUSIONS: Vaporization and smoking provide comparable cannabinoid delivery. CBG and CBN are recent-use cannabis markers after cannabis inhalation, but their absence does not exclude recent use. Multiple, complimentary criteria should be implemented in conjunction with impairment observations to improve interpretation of cannabinoid tests. Clinicaltrials.gov Identifier: NCT02177513

Mass Spectrometry–Based Adrenal and Peripheral Venous Steroid Profiling for Subtyping Primary Aldosteronism

Abstract: BACKGROUND: Differentiating patients with primary aldosteronism caused by aldosterone-producing adenomas (APAs) from those with bilateral adrenal hyperplasia (BAH), which is essential for choice of therapeutic intervention, relies on adrenal venous sampling (AVS)-based measurements of aldosterone and cortisol. We assessed the utility of LC-MS/MS–based steroid profiling to stratify patients with primary aldosteronism. METHODS: Fifteen adrenal steroids were measured by LC-MS/MS in peripheral and adrenal venous plasma from AVS studies for 216 patients with primary aldosteronism at 3 tertiary referral centers. Ninety patients were diagnosed with BAH and 126 with APAs on the basis of immunoassay-derived adrenal venous aldosterone lateralization ratios. RESULTS: Among 119 patients confirmed to have APAs at follow-up, LC-MS/MS–derived lateralization ratios of aldosterone normalized to cortisol, dehydroepiandrosterone, and androstenedione were all higher (P CONCLUSIONS: LC-MS/MS–based steroid profiling during AVS achieves higher aldosterone lateralization ratios in patients with APAs than immunoassay. LC-MS/MS also enables multiple measures for discriminating unilateral from bilateral aldosterone excess, with potential use of peripheral plasma for subtype classification.

Accession of Tumor Heterogeneity by Multiplex Transcriptome Profiling of Single Circulating Tumor Cells

Abstract: BACKGROUND: Transcriptome analysis of circulating tumor cells (CTCs) holds great promise to unravel the biology of cancer cell dissemination and identify expressed genes and signaling pathways relevant to therapeutic interventions. METHODS: CTCs were enriched based on their EpCAM expression (CellSearch®) or by size and deformability (ParsortixTM), identified by EpCAM and/or pan-keratin–specific antibodies, and isolated for single cell multiplex RNA profiling. RESULTS: Distinct breast and prostate CTC expression signatures could be discriminated from RNA profiles of leukocytes. Some CTCs positive for epithelial transcripts (EpCAM and KRT19) also coexpressed leukocyte/mesenchymal associated markers (PTPRC and VIM). Additional subsets of CTCs within individual patients were characterized by divergent expression of genes involved in epithelial–mesenchymal transition (e.g., CDH2, MMPs, VIM, or ZEB1 and 2), DNA repair (RAD51), resistance to cancer therapy (e.g., AR, AR-V7, ERBB2, EGFR), cancer stemness (e.g., CD24 and CD44), activated signaling pathways involved in tumor progression (e.g., PIK3CA and MTOR) or cross talks between tumors and immune cells (e.g., CCL4, CXCL2, CXCL9, IL15, IL1B, or IL8). CONCLUSIONS: Multimarker RNA profiling of single CTCs reveals distinct CTC subsets and provides important insights into gene regulatory networks relevant for cancer progression and therapy.

Measurement by a Novel LC-MS/MS Methodology Reveals Similar Serum Concentrations of Vitamin D–Binding Protein in Blacks and Whites

Abstract: BACKGROUND: Vitamin D deficiency is associated with poor bone health and other adverse health outcomes; however, the associations are greatly attenuated in black vs white individuals. One possible explanation for this attenuation is different concentrations of bioavailable vitamin D metabolites in plasma, which are estimated with equations that include the total concentration of vitamin D binding globulin (VDBG) and haplotype-specific dissociation constants. METHODS: We developed a method to quantify VDBG with LC-MS/MS that could also identify the haplotypes/isoforms of VDBG present. We validated the method according to recent recommendations for publications of biomarker studies. We determined serum VDBG concentrations in samples from the Atherosclerosis Risk in Communities cohort and compared the results with a widely used monoclonal immunoassay. RESULTS: With 10 μL of serum or plasma, the lower limit of quantification for the assay (<20% CV) was 71 μg/mL. The assay was linear from 62 to 434 μg/mL, with total imprecision of 7.3–9.0% CV at approximately 250 μg/mL. Significant hemolysis interfered with quantification. The identification of isoforms was 97% concordant with genotyping (κ coefficient). Method comparison with immunoassay revealed significant isoform-specific effects in the immunoassay. Mean concentrations (SD) of VDBG by mass spectrometry were similar in whites and blacks [262 (25) vs 266 (35) μg/mL, respectively; P = 0.43]. CONCLUSIONS: Validated mass spectrometric methods for the quantification of proteins in human samples can provide additional information beyond immunoassay. Counter to prior observations by immunoassay, VDBG concentrations did not vary by race.

Comprehensive Assessment of M-Proteins Using Nanobody Enrichment Coupled to MALDI-TOF Mass Spectrometry.

Abstract: BACKGROUND: Electrophoretic separation of serum and urine proteins has played a central role in diagnosing and monitoring plasma cell disorders. Despite limitations in resolution and analytical sensitivity, plus the necessity for adjunct methods, protein gel electrophoresis and immunofixation electrophoresis (IFE) remain front-line tests. METHODS: We developed a MALDI mass spectrometry–based assay that was simple to perform, automatable, analytically sensitive, and applicable to analyzing the wide variety of monoclonal proteins (M-proteins) encountered clinically. This assay, called MASS-FIX, used the unique molecular mass signatures of the different Ig isotypes in combination with nanobody immunoenrichment to generate information-rich mass spectra from which M-proteins could be identified, isotyped, and quantified. The performance of MASS-FIX was compared to current gel-based electrophoresis assays. RESULTS: MASS-FIX detected all M-proteins that were detectable by urine or serum protein electrophoresis. In serial dilution studies, MASS-FIX was more analytically sensitive than IFE. For patient samples, MASS-FIX provided the same primary isotype information for 98% of serum M-proteins (n = 152) and 95% of urine M-proteins (n = 55). MASS-FIX accurately quantified M-protein to 0.045 g/dL, with the ability to detect M-proteins CONCLUSIONS: MASS-FIX can advance how plasma cell disorders are screened, diagnosed, and monitored.

Increased Remnant Cholesterol Explains Part of Residual Risk of All-Cause Mortality in 5414 Patients with Ischemic Heart Disease

Abstract: BACKGROUND: Increased concentrations of remnant cholesterol are causally associated with increased risk of ischemic heart disease. We tested the hypothesis that increased remnant cholesterol is a risk factor for all-cause mortality in patients with ischemic heart disease. METHODS: We included 5414 Danish patients diagnosed with ischemic heart disease. Patients on statins were not excluded. Calculated remnant cholesterol was nonfasting total cholesterol minus LDL and HDL cholesterol. During 35836 person-years of follow-up, 1319 patients died. RESULTS: We examined both calculated and directly measured remnant cholesterol; importantly, however, measured remnant cholesterol made up only 9% of calculated remnant cholesterol at nonfasting triglyceride concentrations 5 mmol/L (443 mg/dL). Multivariable-adjusted hazard ratios for all-cause mortality compared with patients with calculated remnant cholesterol concentrations in the 0 to 60th percentiles were 1.2 (95% CI, 1.1–1.4) for patients in the 61st to 80th percentiles, 1.3 (1.1–1.5) for the 81st to 90th percentiles, 1.5 (1.1–1.8) for the 91st to 95th percentiles, and 1.6 (1.2–2.0) for patients in the 96th to 100th percentiles (trend, P < 0.001). Corresponding values for measured remnant cholesterol were 1.0 (0.8–1.1), 1.2 (1.0–1.4), 1.1 (0.9–1.5), and 1.3 (1.1–1.7) (trend, P = 0.006), and for measured LDL cholesterol 1.0 (0.9–1.1), 1.0 (0.8–1.2), 1.0 (0.8–1.3), and 1.1 (0.8–1.4) (trend, P = 0.88). Cumulative survival was reduced in patients with calculated remnant cholesterol ≥1 mmol/L (39 mg/dL) vs <1 mmol/L [log-rank, P = 9 × 10−6; hazard ratio 1.3 (1.2–1.5)], but not in patients with measured LDL cholesterol ≥3 mmol/L (116 mg/dL) vs <3 mmol/L [ P = 0.76; hazard ratio 1.0 (0.9–1.1)]. CONCLUSIONS: Increased concentrations of both calculated and measured remnant cholesterol were associated with increased all-cause mortality in patients with ischemic heart disease, which was not the case for increased concentrations of measured LDL cholesterol. This suggests that increased concentrations of remnant cholesterol explain part of the residual risk of all-cause mortality in patients with ischemic heart disease.

A Study of Hypermethylated Circulating Tumor DNA as a Universal Colorectal Cancer Biomarker

Abstract: Background: Circulating tumor DNA (ctDNA) has emerged as a good candidate for tracking tumor dynamics in different cancer types, potentially avoiding repeated tumor biopsies. Many different genes can be mutated within a tumor, complicating procedures for tumor monitoring, even with highly sensitive next-generation sequencing (NGS) strategies. Droplet-based digital PCR (dPCR) is a highly sensitive and quantitative procedure, allowing detection of very low amounts of circulating tumor genetic material, but can be limited in the total number of target loci monitored. Methods: We analyzed hypermethylation of 3 genes, by use of droplet-based dPCR in different stages of colorectal cancer (CRC), to identify universal markers for tumor follow-up. Results: Hypermethylation of WIF1 (WNT inhibitory factor 1) and NPY (neuropeptide Y) genes was significantly higher in tumor tissue compared to normal tissue, independently of tumor stage. All tumor tissues appeared positive for one of the 2 markers. Methylated ctDNA (MetctDNA) was detected in 80% of metastatic CRC and 45% of localized CRC. For samples with detectable mutations in ctDNA, MetctDNA and mutant ctDNA (MutctDNA) fractions were correlated. During follow-up of different stage CRC patients, MetctDNA changes allowed monitoring of tumor evolution. Conclusions: These results indicate that MetctDNA could be used as a universal surrogate marker for tumor follow-up in CRC patients, and monitoring MetctDNA by droplet-based dPCR could avoid the need for monitoring mutations.

Two-Hour Algorithm for Triage toward Rule-Out and Rule-In of Acute Myocardial Infarction by Use of High-Sensitivity Cardiac Troponin I

Abstract: Background: The early triage of patients towards rule out and rule in of acute myocardial infarction (AMI) is challenging. Therefore, we aimed to develop a 2-h algorithm that uses high-sensitivity cardiac troponin I (hs-cTnI). Methods: We prospectively enrolled 1435 (derivation cohort) and 1194 (external validation cohort) patients presenting with suspected AMI to the emergency department. The final diagnosis was adjudicated by 2 independent cardiologists. hs-cTnI was measured at presentation and after 2 h in a blinded fashion. We derived and validated a diagnostic algorithm incorporating hs-cTnI values at presentation and absolute changes within the first 2 h. Results: AMI was the final diagnosis in 17% of patients in the derivation and 13% in the validation cohort. The 2-h algorithm developed in the derivation cohort classified 56% of patients as rule-out, 17% as rule-in, and 27% for observation. Resulting diagnostic sensitivity and negative predictive value (NPV) were 99.2% and 99.8% for rule-out; specificity and positive predictive value (PPV) were 95.2% and 75.8% for rule-in. Applying the 2-h algorithm in the external validation cohort, 60% of patients were classified as rule-out, 13% as rule-in, and 27% as observation. Diagnostic sensitivity and NPV were 98.7% and 99.7% for rule-out; specificity and PPV were 97.4% and 82.2% for rule-in. Thirty-day survival was 100% for rule-out patients in both cohorts. Conclusions: A simple algorithm incorporating hs-cTnI baseline values and absolute 2-h changes allowed a triage toward safe rule-out or accurate rule-in of AMI in the majority of patients.

Comparison of the Predictive Value of GlycA and Other Biomarkers of Inflammation for Total Death, Incident Cardiovascular Events, Noncardiovascular and Noncancer Inflammatory-Related Events, and Total Cancer Events

Abstract: BACKGROUND: GlycA is a biomarker that reflects integrated concentrations and glycosylation states of several acute-phase proteins. We studied the association of GlycA and inflammatory biomarkers with future death and disease. METHODS: A total of 6523 men and women in the Multi-Ethnic Study of Atherosclerosis who were free of overt cardiovascular disease (CVD) and in generally good health had a baseline blood sample taken. We assayed high-sensitivity C-reactive protein (hsCRP), interleukin-6 (IL-6), and d-dimer. A spectral deconvolution algorithm was used to quantify GlycA signal amplitudes from automated nuclear magnetic resonance (NMR) LipoProfile® test spectra. Median follow-up was 12.1 years. Among 4 primary outcomes, CVD events were adjudicated, death was by death certificate, and chronic inflammatory-related severe hospitalization and death (ChrIRD) and total cancer were classified using International Classification of Diseases (ICD) codes. We used Poisson regression to study baseline GlycA, hsCRP, IL-6, and d-dimer in relation to total death, CVD, ChrIRD, and total cancer. RESULTS: Relative risk per SD of GlycA, IL-6, and d-dimer for total death (n = 915); for total CVD (n = 922); and for ChrIRD (n = 1324) ranged from 1.05 to 1.20, independently of covariates. In contrast, prediction from hsCRP was statistically explained by adjustment for other inflammatory variables. Only GlycA was predictive for total cancer (n = 663). Women had 7% higher values of all inflammatory biomarkers than men and had a significantly lower GlycA prediction coefficient than men in predicting total cancer. CONCLUSIONS: The composite biomarker GlycA derived from NMR is associated with risk for total death, CVD, ChrIRD, and total cancer after adjustment for hsCRP, IL-6, and d-dimer. IL-6 and d-dimer contribute information independently of GlycA.

Interplay between CRP, Atherogenic LDL, and LOX-1 and Its Potential Role in the Pathogenesis of Atherosclerosis

Abstract: BACKGROUND: Studies have shown that the classic acute-phase protein C-reactive protein (CRP) has proinflammatory effects on vascular cells and may play a causal role in the pathogenesis of coronary artery disease. A growing body of evidence has suggested that interplay between CRP, lectin-like oxidized LDL receptor-1 (LOX-1), and atherogenic LDL may underlie the mechanism of endothelial dysfunction that leads to atherosclerosis. CONTENT: We review the biochemical evidence for an association of CRP, LOX-1, and either oxidized LDL (OxLDL) or electronegative L5 LDL with the pathogenesis of coronary artery disease. Artificially oxidized OxLDL has been studied extensively for its role in atherogenesis, as has electronegative L5 LDL, which is present at increased levels in patients with increased cardiovascular risks. OxLDL and L5 have been shown to stimulate human aortic endothelial cells to produce CRP, indicating that CRP is synthesized locally in the endothelium. The ligand-binding face (B-face) of CRP has been shown to bind the LOX-1 scavenger receptor and increase LOX-1 expression in endothelial cells, thereby promoting the uptake of OxLDL or L5 by LOX-1 into endothelial cells to induce endothelial dysfunction. SUMMARY: CRP and LOX-1 may form a positive feedback loop with OxLDL or L5 in atherogenesis, whereby increased levels of atherogenic LDL in patients with cardiovascular risks induce endothelial cells to express CRP, which may in turn increase the expression of LOX-1 to promote the uptake of atherogenic LDL into endothelial cells. Further research is needed to confirm a causal role for CRP in atherogenesis.

CLSI C62-A: A New Standard for Clinical Mass Spectrometry

Abstract: Until recently, there existed minimal guidance on the use of LC-MS for clinical diagnostics. The Clinical and Laboratory Standards Institute (CLSI)2 has now presented a standardized approach for LC-MS assay development and verification in its new guidance document, CLSI C62-A. This document should aid in the harmonization of LC-MS methods and thus have significant ramifications for the evolution of this technology in the clinical laboratory. The ability to accurately identify and quantify a measurand with high sensitivity and specificity by use of selective reaction monitoring has been the driving force for the adoption of LC-MS in the clinical laboratory. LC-MS offers analytical specificity superior to that of widespread diagnostic methodologies such as immunoassays and enzymatic assays. Whereas immunoassays are commonplace in the clinical laboratory, they are not available for all analytes of interest, are plagued by specificity issues, and require the time-consuming production and evaluation of antibodies during development. Just as immunoassays have evolved since their development >50 years ago and have found their place as the leading automated technological approach to diagnostic testing, mass spectrometry (MS) will continue to progress and influence the clinical laboratory landscape. Therefore, standardization of the use of LC-MS is essential. Mass spectrometers were initially used in clinical laboratories only for specialized testing by highly trained and experienced operators. Today they are essential for the diagnosis of metabolic disorders, screening of diseases, quantification of hormone concentrations, monitoring of drug therapies, identification of microbial organisms, and recognition of drug toxicity and poisonings. Without the current clinical quantitative LC-MS methods, metabolic disorders would go undetected at birth, the accuracy of testosterone measurements for women and children would be equivalent to an educated guess, and monitoring of a variety of chemotherapeutics and immunosuppressants would be limited. Despite its widespread use, there is only 1 quantitative LC-MS assay …

Functional Studies on Viable Circulating Tumor Cells

Abstract: BACKGROUND: Research on circulating tumor cells (CTCs) as new biomarkers has received great attention over the past decade. In particular, the capture and analysis of CTCs as “liquid biopsies” provides the possibility to avoid invasive tissue biopsies, with obvious implications in cancer diagnostics. CONTENT: The focus of this review is to describe and discuss how functional studies on viable CTCs can enlarge the spectrum of applications of liquid biopsies, with emphasis on breast, prostate, colon, and lung cancer as the major tumor entities in industrialized countries. The low number of CTCs in the peripheral blood of most cancer patients makes challenging the in vitro culture of CTCs. Epithelial tumor cells are difficult to culture, even when starting with millions of tumor cells. Recently, several groups have achieved important advances in the in vitro and in vivo expansion of CTCs from cancer patients at very advanced stages with higher amounts of CTCs. Here, we present current technologies to enrich and detect viable human CTCs, including positive and negative enrichment strategies that are based on antigen expression and physical properties of CTCs. We also discuss published data about functional studies on CTCs that use in vitro and in vivo models. SUMMARY: Functional analyses on CTCs offer the possibility to identify the biological properties of metastatic cells, including the identification of metastasis-initiating cells. Moreover, CTC-derived cell lines and xenografts might reveal new therapeutic targets and can be used for drug screening.

Short Telomere Length and Ischemic Heart Disease: Observational and Genetic Studies in 290 022 Individuals

Abstract: Background: Short telomeres are associated with aging and have been associated with a high risk of ischemic heart disease in observational studies; however, the latter association could be due to residual confounding and/or reverse causation. We wanted to test the hypothesis that short telomeres are associated with high risk of ischemic heart disease using a Mendelian randomization approach free of reverse causation and of most confounding. Methods: We genotyped 3 genetic variants in OBFC1 (oligonucleotide/oligosaccharide binding fold containing 1), TERT (telomerase reverse transcriptase), and TERC (telomerase RNA component), which code for proteins and RNA involved in telomere maintenance. We studied 105u055 individuals from Copenhagen; 17u235 of these individuals were diagnosed with ischemic heart disease between 1977 and 2013, and 66u618 had telomere length measured. For genetic studies, we further included the Coronary ARtery DIsease Genome wide Replication and Meta-analysis (CARDIoGRAM) consortium dataset, which included up to 184u967 participants and 60u837 cases of ischemic heart disease. We conducted multivariable adjusted Cox proportional hazard models for observational estimates, using logistic and instrumental variable analysis for genetic estimates. Results: Observationally, a 200-bp–shorter telomere length was associated with a multivariable adjusted hazard ratio for ischemic heart disease of 1.02 (95% CI, 1.01–1.03). Per allele, telomeres were shorter by 67 bp (73–60). In meta-analyses of all 4 studies combined, odds ratios for ischemic heart disease were 1.05 (1.03–1.08) for OBCF1 , 1.04 (1.02–1.06) for TERT , and 1.01 (0.99–1.03) for TERC . A genetically determined 200-bp–shorter telomere length was associated with an odds ratio for ischemic heart disease of 1.10 (1.06–1.14). Conclusions: Shorter telomeres were associated with a higher risk of ischemic heart disease, both observationally and genetically.

Circulating Tumor DNA as a Cancer Biomarker: Fact or Fiction?

Abstract: The notion of utilizing cell-free DNA (cfDNA)8 in the circulation as a surrogate biomarker is not a novel concept. Mandel and Metais identified the presence of cfDNA in the blood of healthy individuals almost 60 years ago. Decades later, multiple groups were able to extend the work of Mandel and Metais into the identification of tumor-derived cfDNA—also known as circulating tumor DNA (ctDNA)—in the blood of cancer patients. These findings suggested that a “liquid biopsy” may be a feasible clinical tool because tumors seem to release fragments of DNA into the circulatory system that are both detectable and specific to the tumor. In the past decade, we have witnessed a surge in both new technologies and improvements on existing technologies for sequencing DNA that have made this once-laborious process cheaper and faster. In 2009, the cost of sequencing per genome was $100 000, whereas in 2014, this cost dropped to $5000 (taking into account labor, administration, management, utilities, reagents, and consumables). As a result, the use of ctDNA as a liquid biopsy has become ever more feasible. Clinically speaking, a ctDNA-based liquid biopsy would be the optimal mode of cancer management owing to various advantages including: ( a ) Retrieval of ctDNA would be minimally invasive especially compared to a tissue biopsy; ( b ) ctDNA could provide a full representation of the tumor (as well as any clonal metastases); and ( c ) ctDNA would provide a personalized snapshot of the patient's disease. Although the clinical use of ctDNA as a surrogate biomarker is still hampered by biological and technological hurdles, the implications of a liquid biopsy could be enormous as there would be numerous potential applications including (but not limited to): early detection, monitoring of minimal residual disease (MRD), assessment of treatment response, and triaging based on risk of recurrence. In this Q&A …

Ion Mobility in Clinical Analysis: Current Progress and Future Perspectives.

Abstract: BACKGROUND: Ion mobility spectrometry (IMS) is a rapid separation tool that can be coupled with several sampling/ionization methods, other separation techniques (e.g., chromatography), and various detectors (e.g., mass spectrometry). This technique has become increasingly used in the last 2 decades for applications ranging from illicit drug and chemical warfare agent detection to structural characterization of biological macromolecules such as proteins. Because of its rapid speed of analysis, IMS has recently been investigated for its potential use in clinical laboratories. CONTENT: This review article first provides a brief introduction to ion mobility operating principles and instrumentation. Several current applications will then be detailed, including investigation of rapid ambient sampling from exhaled breath and other volatile compounds and mass spectrometric imaging for localization of target compounds. Additionally, current ion mobility research in relevant fields (i.e., metabolomics) will be discussed as it pertains to potential future application in clinical settings. SUMMARY: This review article provides the authors9 perspective on the future of ion mobility implementation in the clinical setting, with a focus on ambient sampling methods that allow IMS to be used as a “bedside” standalone technique for rapid disease screening and methods for improving the analysis of complex biological samples such as blood plasma and urine.

Biological Variation: The Effect of Different Distributions on Estimated Within-Person Variation and Reference Change Values

Abstract: BACKGROUND: Good estimates of within-person biological variation, CVI, are essential for diagnosing and monitoring patients and for setting analytical performance specifications. The aim of the present study was to use computer simulations to evaluate the impact of various measurement distributions on different methods for estimating CVI and reference change value (RCV). METHOD: Data were simulated on the basis of 3 models for distributions of the within-person effect. We evaluated 3 different methods for estimating CVI: standard ANOVA, ln-ANOVA, and CV-ANOVA, and 3 different methods for calculating RCV: classic, ln-RCV, and a nonparametric method. We estimated CVI and RCV with the different methods and compared the results with the true values. RESULTS: The performance of the methods varied, depending on both the size of the CVI and the type of distributions. The CV-ANOVA model performed well for the estimation of CVI with all simulated data. The ln-RCV method performed best if data were ln-normal distributed or CVI was less than approximately 12%. The nonparametric RCV method performed well for all simulated data but was less precise. CONCLUSIONS: The CV-ANOVA model is recommended for both calculation of CVI and the step-by-step approach of checking for outliers and homogeneity in replicates and samples. The standard method for calculation of RCV should not be used when using CVs.

Clinical significance of circulating tumor microemboli as a prognostic marker in patients with pancreatic ductal adenocarcinoma

Abstract: BACKGROUND: Characterization of circulating tumor cells (CTCs) has been used to provide prognostic, predictive, and pharmacodynamic information in many different cancers. However, the clinical significance of CTCs and circulating tumor microemboli (CTM) in patients with pancreatic ductal adenocarcinoma (PDAC) has yet to be determined. METHODS: In this prospective study, CTCs and CTM were enumerated in the peripheral blood of 63 patients with PDAC before treatment using anti-EpCAM (epithelial cell adhesion molecule)–conjugated supported lipid bilayer–coated microfluidic chips. Associations of CTCs and CTM with patients' clinical factors and prognosis were determined. RESULTS: CTCs were abundant [mean (SD), 70.2 (107.6)] and present in 81% (51 of 63) of patients with PDAC. CTM were present in 81% (51 of 63) of patients with mean (SD) 29.7 (1101.4). CTM was an independent prognostic factor of overall survival (OS) and progression free survival (PFS). Patients were stratified into unfavorable and favorable CTM groups on the basis of CTM more or less than 30 per 2 mL blood, respectively. Patients with baseline unfavorable CTM, compared with patients with favorable CTM, had shorter PFS (2.7 vs 12.1 months; P < 0.0001) and OS (6.4 vs 19.8 months; P < 0.0001). Differences persisted if we stratified patients into early and advanced diseases. The number of CTM before treatment was an independent predictor of PFS and OS after adjustment for clinically significant factors. CONCLUSIONS: The number of CTM, instead of CTCs, before treatment is an independent predictor of PFS and OS in patients with PDAC.

Detection of KRAS Mutations in Circulating Tumor DNA by Digital PCR in Early Stages of Pancreatic Cancer

Abstract: BACKGROUND: Since surgical removal remains the only cure for pancreatic cancer, early detection is of utmost importance. Circulating biomarkers have potential as diagnostic tool for pancreatic cancer, which typically causes clinical symptoms only in advanced stage. Because of their high prevalence in pancreatic cancer, KRAS proto-oncogene, GTPase [ KRAS (previous name: Kirsten rat sarcoma viral oncogene homolog)] mutations may be used to identify tumor-derived circulating plasma DNA. Here we tested the diagnostic sensitivity of chip based digital PCR for the detection of KRAS mutations in circulating tumor DNA (ctDNA) in early stage pancreatic cancer. METHODS: We analyzed matched plasma (2 mL) and tumor samples from 50 patients with pancreatic cancer. Early stages (I and II) were predominant (41/50) in this cohort. DNA was extracted from tumor and plasma samples and tested for the common codon 12 mutations G12D, G12V, and G12C by chip-based digital PCR. RESULTS: We identified KRAS mutations in 72% of the tumors. 44% of the tumors were positive for G12D, 20% for G12V, and 10% for G12C. One tumor was positive for G12D and G12V. Analysis of the mutations in matched plasma samples revealed detection rates of 36% for G12D, 50% for G12V, and 0% for G12C. The detection appeared to be correlated with total number of tumor cells in the primary tumor. No KRAS mutations were detected in 20 samples of healthy control plasma. CONCLUSIONS: Our results support further evaluation of tumor specific mutations as early diagnostic biomarkers using plasma samples as liquid biopsy.

Automated Multiplex LC-MS/MS Assay for Quantifying Serum Apolipoproteins A-I, B, C-I, C-II, C-III, and E with Qualitative Apolipoprotein E Phenotyping

Abstract: BACKGROUND: Direct and calculated measures of lipoprotein fractions for cardiovascular risk assessment suffer from analytical inaccuracy in certain dyslipidemic and pathological states, most commonly hypertriglyceridemia. LC-MS/MS has proven suitable for multiplexed quantification and phenotyping of apolipoproteins. We developed and provisionally validated an automated assay for quantification of apolipoprotein (apo) A-I, B, C-I, C-II, C-III, and E and simultaneous qualitative assessment of apoE phenotypes. METHODS: We used 5 value-assigned human serum pools for external calibration. Serum proteins were denatured, reduced, and alkylated according to standard mass spectrometry–based proteomics procedures. After trypsin digestion, peptides were analyzed by LC-MS/MS. For each peptide, we measured 2 transitions. We compared LC-MS/MS results to those obtained by an immunoturbidimetric assay or ELISA. RESULTS: Intraassay CVs were 2.3%–5.5%, and total CVs were 2.5%–5.9%. The LC-MS/MS assay correlated ( R = 0.975–0.995) with immunoturbidimetric assays with Conformite Europeenne marking for apoA-I, apoB, apoC-II, apoC-III, and apoE in normotriglyceridemic (n = 54) and hypertriglyceridemic (n = 46) sera. Results were interchangeable for apoA-I ≤3.0 g/L (Deming slope 1.014) and for apoB-100 ≤1.8 g/L (Deming slope 1.016) and were traceable to higher-order standards. CONCLUSIONS: The multiplex format provides an opportunity for new diagnostic and pathophysiologic insights into types of dyslipidemia and allows a more personalized approach for diagnosis and treatment of lipid abnormalities.