Showing papers in "Medical laboratory sciences in 1991"

The microbiology of drinking water.

Abstract: Standards for drinking water have been formalised in the United Kingdom by recent legislation. Routine microbiological monitoring of water supplies is primarily based on tests for coliforms. These organisms have been used successfully for indicating contamination and treatment failures, but may need supplementing with other organisms to further improve confidence in water supply hygiene. Novel techniques may greatly alter the water microbiology laboratory.

Mycotoxins in food.

Abstract: The presence of mycotoxins in a wide range of foodstuffs can lead to many different toxic conditions in both man and domestic animals. The major fungi responsible for producing these toxins are species of Aspergillus, Penicillium, Fusarium and Alternaria, although other genera are involved as well, for example Claviceps, Diplodia and Arthrinium. An overview is given of the major mycotoxins responsible for illnesses following ingestion of contaminated foods, with particular emphasis on the effects produced in humans. Compounds discussed include the aflatoxins, cyclopiazonic acid, tenuazonic acid, the trichothecenes, zearalenone, wortmannin, fumonisins B1 and B2, patulin, ochratoxin A, diplodiatoxin and diplosporin.

The immunological status in Parkinson's disease.

Abstract: It has been suggested that patients with idiopathic Parkinson's disease have altered functions of the immune system. We determined certain immunological parameters in groups of Parkinson's disease patients who have been i) treated and ii) not been treated, with levodopa. Changes in the immune functions were observed to be more profound in Parkinson's disease patients than in age-matched controls. Treatment with levodopa induced an increase in interleukin-1 synthesis, and in IgM and IgA levels in plasma, which suggest a possible selective action on cells of the immune system.

Malaria screening to prevent transmission by transfusion: an evaluation of techniques.

Abstract: Transfusion-associated malaria is often severe or even fatal, because diagnosis is frequently delayed and it complicates an already serious underlying disorder. Detection of infected donors is difficult in endemic areas due to the lack of a suitable donor screening test. Blood smear staining techniques show poor results due to the low parasite concentration in many infected persons, and the antibody detection test is not helpful due to the universal presence of antibody in healthy donors in these areas. For comparative evaluation of various screening tests, 9131 blood smears from voluntary donors and a group of patients were screened by Giemsa staining. Ten (0.10%) subjects showed parasitaemia, whereas Acridine Orange fluorescence staining showed 13 (0.14%) parasitaemia in almost the same number of smears screened on the same samples. Significantly high levels of malarial antibody were detected in 12.6% and 19.86% of subjects by indirect fluorescent antibody and enzyme-linked immunoassay tests, respectively. Malarial antigen detection by monoclonal antibody showed positive results in 9.48% of subjects, demonstrating excellent results and showing direct evidence of infection. We recommend that this should be adopted as a screening technique by transfusion services in endemic areas in order to prevent post transfusion malaria.

Lectin binding to normal mucosa, leukoplakia and squamous cell carcinoma of the oral cavity.

Abstract: A panel of fifteen biotinylated lectins was used to study the saccharides associated with the epithelial component of normal and leukoplakic mucosa and squamous cell carcinoma, from a variety of locations in the oral cavity Lectin binding heterogeneity was found between various sites of normal mucosa The binding to leukoplakic epithelium closely resembled normal, with similar site heterogeneity However, the features of cell-capping and cellular expression of the blood group A antigen, as observed in normal and most leukoplakic epithelia, were not observed in squamous cell carcinoma These results show that neoplasia in oral squamous epithelium is associated with alterations in terminal N-acetyl-D-galactosamine, N-acetyl-D-glucosamine, D-mannose, L-fucose, D-glucosamine and D-galactosamine residues present in the outer parts of both O-linked and N-linked glycoconjugates, along with high levels of terminal sialation of certain residues

Detection of toxoplasma-specific immunoglobulin-G: assessment of a slide agglutination test.

Abstract: The performance of a slide agglutination test for detection of toxoplasma-specific IgG was assessed and compared with that of the dye test and latex agglutination test. The slide agglutination test was as sensitive as, and more specific than, latex agglutination. The predictive value of a negative slide agglutination test was less than the latex agglutination test but produced results within minutes, although quantitative results were not comparable to other assays. Slide agglutination presents a rapid alternative to the latex agglutination test as a screening assay for toxoplasmosis, although patients at risk of life-threatening infection require detailed serological examination using additional methods.

Early detection of lower respiratory tract infection: the value of the gram-stained sputum smear.

Abstract: In some clinical laboratories the routine examination of sputum includes a Gram-stained smear. Of specimens examined in this study the Gram-stained smear was found to be useful, but fallible in predicting bacterial culture results. Smear results requested urgently by clinicians should be relayed with caution. However, the predictive negative value of the Gram stain was encouraging.

A whole blood control for blood count analysers, and source material for an external quality assessment scheme.

Abstract: An inexpensive and simple to prepare stable whole blood control material for blood count analysers has been evaluated. The material has been used for an external quality assessment scheme for 3 years, and during part of this period as a calibrant for two aperture impedance devices.

Recovery of Mycoplasma hominis from blood culture media.

Abstract: Although several workers have demonstrated that Mycoplasma hominis is responsible for 2 to 20% of cases of septicaemia, reports from Britain do not support this premise--possibly because many of the blood culture systems used fail to sustain growth of this organism. Previous work suggests that this is probably due to the inhibitory effects of sodium polyanethol sulphonate (Liquoid) on M. hominis. In an extension of an in-vitro evaluation of blood culture systems, gelatin was shown to give some protection against the inhibitory effect of polyanethol sulphonate on M. hominis. Of 20 systems evaluated, Becton Dickinson's Supplemented Peptone Broth in their Vacutainer collection system was the most successful at recovering M. hominis.

Continuous ambulatory peritoneal dialysis: factors influencing recovery of organisms from effluents.

Abstract: In order to establish reasons for a decreased yield of positive culture results from peritoneal dialysates of patients with continuous ambulatory dialysis peritonitis 60 specimens were examined, 47 (78%) of which were positive. A negative result was associated with a delay in processing the specimen and the presence of antimicrobial substances in the dialysate. The application of a method involving dilution of a large volume of effluent in broth did not substantially increase the positive yield.

Rheumatoid factor quantitation: a comparison of ELISA and nephelometric methods.

Abstract: Quantitation of rheumatoid factors (RF) by nephelometry, and more recently by enzyme linked immunosorbent assay (ELISA), are achieving increasingly common usage. Sera from 101 rheumatoid patients were compared by both methods and screened by a latex fixation method. Good correlation was found between the two assay techniques, the ELISA showing greater sensitivity and measuring IgG RF and IgA RF in addition to IgM RF. Both assay methods were reliable, accurate, rapid and sensitive for routine clinical purposes.

Aluminium, amyloid, and Alzheimer's disease

Abstract: Alzheimer's disease is a degenerative disease characterized by the presence of numerous senile plaques and neurofibrillary tangles, primarily in the cortical areas of the brain. There is no known cause of the disease, although exposure to aluminium has been implicated by epidemiological studies and the finding of aluminium in the cerebral plaques and tangles. There is a genetic predisposition for early-onset disease, and Down's syndrome patients are particularly vulnerable. Many of the plaques contain amyloid, and a gene for amyloid precursor protein has been identified on the long arm of chromosome 21. It is possible that the amyloid plaques arise through over-expression of this gene. Since there is no specific marker for Alzheimer's disease, laboratory investigations are restricted to confirming the disease after the patient has died. Recent immunohistochemical studies have been directed towards showing the relationships between the neurones, senile plaques and neurofibrillary tangles, and the presence of amyloid and filament proteins such as tau, ubiquitin and neurofilaments.

Liquid chromatographic analysis of amino acids in physiological fluids: recent advances.

Abstract: Amino acid analysers have been used for the quantitative investigation of amino acids in physiological fluids for over 30 years. Advances in technology have resulted in a steady decrease in analysis time and detection limits of the cation-exchange chromatography, followed by ninhydrin detection, used by the original instruments. The introduction of pre-column derivatisation and alternative HPLC techniques offers new opportunities for advancement. The analytical characteristics, principles, merits and limitations of both techniques are discussed, and their suitability for clinical purposes assessed. Practical considerations are emphasised and the influence of choice of chemistry and instrument design on the resolution and quality of quantitative data is highlighted.

Detection of Staphylococcus aureus in blood cultures: evaluation of a two-hour method.

Abstract: Aurease--one of three tests on the RAPIDEC staph system for two-hour identification of the main clinically important staphylococci--was used for the direct detection of Staphylococcus aureus from 102 blood culture broths in which Gram-positive cocci were seen. A pellet of centrifuged blood culture broth was used as the inoculum. The method was compared with the thermonuclease test and subsequent isolates subjected to probabilistic identification based on biochemical reactions. A positive aurease test and the presence of thermonuclease were detected in 27 samples, subsequent identification showing all to be Staph. aureus. A further Staph. aureus strain was aurease negative but thermonuclease positive. None of the remaining 74 specimens was positive by the aurease test, which is rapid, sensitive and specific for detection of Staph. aureus in blood culture broths.

Microwave ovens: mapping the electrical field distribution.

Abstract: Uniformity of electric field intensity of microwaves within the microwave oven cavity is necessary to ensure even load-heating, and is particularly important in pathology procedures where small volume irradiation is carried out. A simple and rapid method for mapping electric field distribution, using reversible thermographic paint, is described. Spatial heating patterns for various positions, and the effects of introducing dummy loads to modify heating distributions, have been obtained for a dedicated microwave processor, and comparison made with a domestic microwave oven.

Haemoglobin in stools from neonates: measurement by a modified Apt-test.

Abstract: The Apt test for the detection of fetal haemoglobin in stool samples from neonates is described. This test has been previously reported to be helpful in the diagnosis of the swallowed blood syndrome in neonates, giving rise to 'melena neonatorum'. In this syndrome it is important to distinguish between swallowed maternal blood at the time of delivery from blood derived from the neonatal gastrointestinal tract. A spectrophotometric improvement has been made to the originally described Apt test, with additional recommendations for use.

Blood group chimaerism: a possible further example.

Abstract: A blood group chimaera is described whose red blood cells exhibit a dual population of group A1 and O, in the proportions 20% and 80% respectively. These results could also indicate a blood group mosaic of the Amos type, but family studies, secretor and transferase investigations on this patient suggest that blood group chimaerism of unestablished type is more likely. There was no further evidence of chimaerism found during cytogenetic investigations, immunoglobulin allotyping or studies of red cell enzyme systems. Blood group chimaeras were previously thought to be rare, as dual red cell populations and the resulting mixed-field agglutination patterns are not always easy to recognise. This case is the second example of chimaerism found within two years in a single routine laboratory, appearing to confirm the view that chimaerism is not as uncommon as previously thought.

A rapid test to detect the most clinically significant Staphylococcus species.

Abstract: A new two-hour test system (RAPIDEC staph) to detect the main staphylococci was evaluated. Of 124 reference strains tested, 83 represented species most often found in clinical specimens, the remaining 41 strains representing five species primarily of animal origin. RAPIDEC staph detected all Staph, aureus, Staph. epidermidis and seven of eight Staph. saprophyticus strains. Of the animal species, all Staphylococcus intermedius strains were assigned to the correct category, the remainder were misidentified as Staph. epidermidis. With 121 catalase-positive Gram-positive cocci isolated from urines the test system correctly detected all Staph. aureus strains, 39 of 41 Staph. epidermidis, and 34 of 36 Staph. saprophyticus. Of 25 atypical Staph. aureus strains which were either slide or tube coagulase negative the test system correctly detected all 17 slide coagulase negative strains but failed to detect eight which were tube coagulase negative. There were no false positives. RAPIDEC staph is a rapid, accurate system for the detection of the three main clinically important species of staphylococci.

Detection of cannabinoids in urine: a cost-effective low risk immunoassay procedure.

Abstract: Using Syva EMIT reagents and a Cobas Bio centrifugal analyser we have developed a cost-effective assay for the detection of cannabinoids in urine. With this method, up to 1500 samples can be assayed with a single 100 test kit while maintaining acceptable precision. A mean CV of 6.1% was obtained for the concentration range 80-130 micrograms/l. The method is suitable for high-risk urines since heart treatment may be performed prior to analysis. There was no significant change in the measured concentration of cannabinoids in urine samples on storage in plastic containers, refrigerated or frozen, for up to seven weeks.

Plasma vitamin B12 binding proteins correlate with disease activity in patients with rheumatoid arthritis.

Abstract: The unsaturated vitamin B12 (cobalamin) binding capacity (UB12BC), transcobalamin (TC) I, II and III were measured in plasma and synovial fluid of 55 patients (10 men and 45 women, 25-60 years of age) with rheumatoid arthritis. The vitamin B12 binding proteins in 55 clinically and haematologically normal subjects of similar age group and sex were also studied as controls. The mean plasma concentrations of UB12BC, TCI, II and III were all significantly raised in patients with rheumatoid arthritis (RA) as compared to the normal controls. The increase of all vitamin B12 binding proteins in these patients showed a positive correlation with the increase of total proteins and globulin concentrations, and a negative (inverse) correlation with the albumin concentrations in the plasma, suggesting that these biochemical changes may be systemic consequences of the inflammatory and immunological processes characteristic of rheumatoid arthritis. The UB12BC, TC I and TC III concentrations in the synovial fluid were significantly higher than the corresponding plasma concentrations of these vitamin B12 binding proteins in patients with RA. Vitamin B12 binding proteins in the synovial fluid in these patients were probably at least partly produced locally by inflammatory cells. The mean levels of plasma transcobalamins in patients with severe disease activity were significantly higher than in patients with median or least disease activity. Therefore these proteins may be further studied as possible additional markers of disease activity in patients with RA.

Treatment and disposal of clinical and laboratory waste.

Abstract: There are no entirely satisfactory definitions of clinical waste; nor are there methods in general use that are safe and environmentally acceptable for the storage, transport and final disposal of the ever-increasing volume of such waste that is generated by the health services. Hazardous, potentially infectious and aesthetically objectionable waste has been found on beaches and exposed on domestic refuse landfill sites, causing public disquiet about health hazards and environmental pollution. Landfill is officially discouraged, where not illegal, and many older-type incinerators can not now be used because their effluent pollutes the atmosphere. Modern and efficient incinerators are expensive and the parochial nature of health service management and accounting mitigates against their installation and use. Laboratory waste, however, can be rendered safe and unobjectionable, aesthetically and environmentally, if the requirements and recommendations of the several Codes of Practice and technical advice, which are simple and inexpensive, are implemented by laboratory and hospital managers.

Discovery of unsuspected pathological states using a new haematology analyser.

Abstract: A new haematology analyser--the Sysmex NE-8000--provides among other results a bi-dimensional representation of leucocyte populations. Unusual patterns are frequently observed due to platelet aggregation or fibrin polymerisation, and a specific 'rocket-shaped' pattern is also sometimes noted. During a seven month period of routine use 68 such cases were investigated, revealing that this pattern is associated with either severe hepatic dysfunction responsible for patient admission or with various asymptomatic constitutional haemoglobin anomalies. This 'rocket' phenomenon is probably due to incomplete erythrocyte lysis in the leucocyte detector. In some cases it causes spurious leucocyte counting (avoidable by a 1 in 5 pre-dilution of the sample), and alteration of the differential count. To take advantage of this aberrant pattern and to orientate immediate complementary investigations on the basis only of the NE-8000 results, we established a discriminative index.

Platelet indices: intra-individual variation in pre- and post-menopausal females.

Abstract: Blood platelet counts and mean platelet volumes were determined at weekly intervals for eight weeks in 13 pre-menopausal and 11 post-menopausal females. Samples were analysed exactly two hours after blood collection on a Coulter S plus VTM particle counter. Pre-menopausal platelet counts were slightly higher than post-menopausal counts at each week, but the count was not affected by the menstrual cycle, intra-individual variation showing mean coefficients of variation (CV) of 7.4% and 5.2% respectively. The mean platelet volume was similar in pre- and post-menopausal groups at each week and showed little variability over time (mean CV 2.7% and 3.3%, respectively). Platelet parameters show little variability over time in either group and with no cyclical effects of menstruation apparent.

Pneumocystis carinii pneumonia: detection of parasites by immunofluorescence based on a monoclonal antibody.

Abstract: A monoclonal antibody-based immunofluorescence test for the detection of Pneumocystis carinii was evaluated in comparison with the conventional direct staining by Grocott's silver methenamine technique. A total of 254 respiratory samples from HIV positive and other immunocompromised patients were examined. Cysts were detected in 30 (12%) of samples using the monoclonal test, but only 15 (6%) positives were found using the Grocott method. There is need for a speedy and efficient test for detection of these organisms, and the monoclonal test was found to be more reliable, quicker and more sensitive than the Grocott technique.

Enzyme techniques in blood group serology: the effect of ionic strength.

Abstract: Lowering the ionic strength of the solution in which red blood cells were suspended for blood grouping was shown to increase sensitivity and the incidence of 'false' positive results in various papain techniques. A reduction in ionic strength of the solution in which cells were pre-modified increased the titration scores for 'enzyme-only' anti-c, anti-e, anti-E and anti-D. Suspension of papain pre-modified cells in lower strength solutions for antigen/antibody reactions had the same effect.

Multidrug resistance in haematological malignancies.

Abstract: Many patients with haematological disorders develop resistance to the drugs used in the treatment of their condition. This resistance is often effective against a range of chemotherapeutic agents, hence the term multidrug resistance (MDR) is used. During the past ten years the mechanisms underlying the development of MDR have become better understood, and in this Review the current concepts of the factors contributing to MDR are examined.

A computerised spreadsheet for audit of a microbiology laboratory.

Abstract: The use of a microcomputer and spreadsheet software is described, to assist in the audit of a clinical microbiology laboratory. The costs of consumables for specimen types and their workload values were calculated. Together with knowledge of the annual number of requests, these were used as a basis for determining the minimum budget and staffing establishment required.

Tissue banking: the role of the Regional Blood Centre: an American experience in Minnesota.

Abstract: The clinical use of bone, cornea, skin, connective tissue and heart valve allografts has increased greatly in the past several years, with bone the most commonly transplanted tissue. Tissue allografts have been the vehicle to transmit infectious disease from donor to recipient. Provision of safe and effective tissue has gradually developed and improved as regional tissue banks have organized, and standards of practice evolved. Regional Blood Centres have the special capabilities and experience to provide the expertise required in tissue banking. Consequent to these community needs, regional bone and tissue banks have been established in blood banks and the experience of the American Red Cross in St Paul, Minnesota is described.