Objective: Diagnostic criteria for coeliac disease (CD) from the European Society for Paediatric Gastroenterology, Hepatology, and Nutrition (ESPGHAN) were published in 1990. Since then, the autoantigen in CD, tissue transglutaminase, has been identified; the perception of CD has changed from that of a rather uncommon enteropathy to a common multiorgan disease strongly dependent on the haplotypes human leukocyte antigen (HLA)-DQ2 and HLA-DQ8; and CD-specific antibody tests have improved. Methods: A panel of 17 experts defined CD and developed new diagnostic criteria based on the Delphi process. Two groups of patients were defined with different diagnostic approaches to diagnose CD: children with symptoms suggestive of CD (group 1) and asymptomatic children at increased risk for CD (group 2). The 2004 National Institutes of Health/ Agency for Healthcare Research and Quality report and a systematic literature search on antibody tests for CD in paediatric patients covering the years 2004 to 2009 was the basis for the evidence-based recommendations on CD-specific antibody testing. Results: In group 1, the diagnosis of CD is based on symptoms, positive serology, and histology that is consistent with CD. If immunoglobulin A anti-tissue transglutaminase type 2 antibody titers are high (>10 times the upper limit of normal), then the option is to diagnose CD without duodenal biopsies by applying a strict protocol with further laboratory tests. In group 2, the diagnosis of CD is based on positive serology and histology. HLADQ2 and HLA-DQ8 testing is valuable because CD is unlikely if both haplotypes are negative. Conclusions: The aim of the new guidelines was to achieve a high diagnostic accuracy and to reduce the burden for patients and their families. The performance of these guidelines in clinical practice should be evaluated prospectively. (JPGN 2012;54: 136–160)

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European Society for Pediatric Gastroenterology, Hepatology, and Nutrition Guidelines for the Diagnosis of Coeliac Disease

Objective The literature suggests a lack of consensus on the use of terms related to coeliac disease (CD) and gluten. Design A multidisciplinary task force of 16 physicians from seven countries used the electronic database PubMed to review the literature for CD-related terms up to January 2011. Teams of physicians then suggested a definition for each term, followed by feedback of these definitions through a web survey on definitions, discussions during a meeting in Oslo and phone conferences. In addition to ‘CD’, the following descriptors of CD were evaluated (in alphabetical order): asymptomatic, atypical, classical, latent, non-classical, overt, paediatric classical, potential, refractory, silent, subclinical, symptomatic, typical, CD serology, CD autoimmunity, genetically at risk of CD, dermatitis herpetiformis, gluten, gluten ataxia, gluten intolerance, gluten sensitivity and gliadin-specific antibodies. Results CD was defined as ‘a chronic small intestinal immune-mediated enteropathy precipitated by exposure to dietary gluten in genetically predisposed individuals’. Classical CD was defined as ‘CD presenting with signs and symptoms of malabsorption. Diarrhoea, steatorrhoea, weight loss or growth failure is required.’ ‘Gluten-related disorders’ is the suggested umbrella term for all diseases triggered by gluten and the term gluten intolerance should not to be used. Other definitions are presented in the paper. Conclusion This paper presents the Oslo definitions for CD-related terms.

https://gut.bmj.com/content/gutjnl/62/1/43.full.pdf

The Oslo definitions for coeliac disease and related terms

Rotavirus infection frequency and risk of celiac disease autoimmunity in early childhood: a longitudinal study.

Femtosecond laser-based generation of radio frequency signals has produced astonishing improvements in achievable spectral purity, one of the basic features characterizing the performance of an radio frequency oscillator. Kerr frequency combs hold promise for transforming these lab-scale oscillators to chip-scale level. In this work we demonstrate a miniature 10 GHz radio frequency photonic oscillator characterized with phase noise better than -60 dBc Hz(-1) at 10 Hz, -90 dBc Hz(-1) at 100 Hz and -170 dBc Hz(-1) at 10 MHz. The frequency stability of this device, as represented by Allan deviation measurements, is at the level of 10(-10) at 1-100 s integration time-orders of magnitude better than existing radio frequency photonic devices of similar size, weight and power consumption.

/pdf/high-spectral-purity-kerr-frequency-comb-radio-frequency-102weyxe8v.pdf

High spectral purity Kerr frequency comb radio frequency photonic oscillator

The outstanding phase-noise performance of optical frequency combs has led to a revolution in optical synthesis and metrology, covering a myriad of applications, from molecular spectroscopy to laser ranging and optical communications However, the ideal characteristics of an optical frequency comb are application dependent In this review, the different techniques for the generation and processing of high-repetition-rate (>10GHz) optical frequency combs with technologies compatible with optical communication equipment are covered Particular emphasis is put on the benefits and prospects of this technology in the general field of radio-frequency photonics, including applications in high-performance microwave photonic filtering, ultra-broadband coherent communications, and radio-frequency arbitrary waveform generation

https://onlinelibrary.wiley.com/doi/pdf/10.1002/lpor.201300126

Optical frequency comb technology for ultra‐broadband radio‐frequency photonics

Objective. At-risk groups commonly undergo screening for autoantibodies associated with celiac disease (CD). However, the clinical significance of a positive test remains uncertain. The objective of this study was to evaluate growth and clinical features of children who test positive for an autoantibody associated with CD. Methods. A case-control study of Denver area healthy infants and young children with and without CD autoantibodies was conducted. A cohort of HLA-characterized children were followed prospectively since birth for the development of immunoglobulin A antitissue transglutaminase autoantibodies (TG). Clinical evaluation, questionnaire, blood draw, and small bowel biopsy were performed. Growth and nutrition and frequency of positive responses were measured. Results. Compared with 100 age- and gender-matched TG-negative controls, 18 TG-positive children, 5.5 ± 0.5 years of age, had a greater number of symptoms and lower z scores for weight-for-height and for body mass index. Responses that were independently associated with TG-positive status were irritability/lethargy, abdominal distention/gas, and difficulty with weight gain. Conclusions. Screening-identified TG-positive children demonstrate mild alterations in growth and nutrition and report more symptoms than control subjects. Additional study is needed on the benefit and risk of identifying CD in at-risk groups.

Clinical features of children with screening-identified evidence of celiac disease

We utilized and characterized high-power, high-linearity modified unitraveling carrier (MUTC) photodiodes for low-phase-noise photonic microwave generation based on optical frequency division (OFD). When illuminated with picosecond pulses from a repetition-rate-multiplied gigahertz Ti:sapphire modelocked laser, the photodiodes can achieve a 10 GHz signal power of +14  dBm. Using these diodes, we generated a 10 GHz microwave tone with less than 500 attoseconds absolute integrated timing jitter (1 Hz–10 MHz) and a phase noise floor of −177  dBc/Hz.We also characterized the electrical response, amplitude-to-phase conversion, saturation, and residual noise of the MUTC photodiodes.

Photonic microwave generation with high-power photodiodes

The generation of microwaves from optical signals suffers from thermal and shot noise inherent in the photodetection process. This problem is more acute at lower pulse repetition rates where photodiode saturation limits the achievable signal-to-noise ratio. In this paper, we demonstrate a 10-15-dB reduction in the 10-GHz phase noise floor by multiplication of the pulse repetition rate. Starting with a 250-MHz fundamentally mode-locked erbium (Er):fiber laser, we compare the following two different approaches to repetition rate multiplication: 1) Fabry-Perot cavity filtering and 2) a cascaded, unbalanced Mach-Zehnder (MZ) fiber-based interferometer. These techniques reduce the phase noise floor on the 10-GHz photodetected harmonic to -158 and -162 dBc/Hz, respectively, for Fourier frequencies higher than 100 kHz.

/pdf/noise-floor-reduction-of-an-er-fiber-laser-based-photonic-26n423uk1l.pdf

Noise Floor Reduction of an Er:Fiber Laser-Based Photonic Microwave Generator

The generation of microwaves from optical signals suffers from thermal and shot noise inherent in the photodetection process. This problem is more acute at lower pulse repetition rates where photodiode saturation limits the achievable signal-to-noise ratio. In this paper, we demonstrate a 10-15 dB reduction in the 10 GHz phase noise floor by multiplication of the pulse repetition rate. Starting with a 250 MHz fundamentally mode-locked erbium(Er):fiber laser, we compare two different approaches to repetition rate multiplication: Fabry-Perot cavity filtering and a cascaded, unbalanced Mach-Zehnder fiber-based interferometer. These techniques reduce the phase noise floor on the 10 GHz photodetected harmonic to -158 dBc/Hz and -162 dBc/Hz, respectively, for Fourier frequencies higher than 100 kHz.

Noise floor reduction of an Er:fiber laser-based photonic microwave generator

We utilize and characterize high-power, high-linearity modified uni-traveling carrier (MUTC) photodiodes for low-phase-noise photonic microwave generation based on optical frequency division. When illuminated with picosecond pulses from a repetition-rate-multiplied gigahertz Ti:sapphire modelocked laser, the photodiodes can achieve 10 GHz signal power of +14 dBm. Using these diodes, a 10 GHz microwave tone is generated with less than 500 attoseconds absolute integrated timing jitter (1 Hz-10 MHz) and a phase noise floor of -177 dBc/Hz. We also characterize the electrical response, amplitude-to-phase conversion, saturation and residual noise of the MUTC photodiodes.

Jennifer Taylor

Papers

Clinical features of children with screening-identified evidence of celiac disease

Photonic microwave generation with high-power photodiodes

Noise Floor Reduction of an Er:Fiber Laser-Based Photonic Microwave Generator

Noise floor reduction of an Er:fiber laser-based photonic microwave generator

Photonic microwave generation with high-power photodiodes