BACKGROUND External quality assessment (EQA) with commutable samples is essential for assessing the quality of assays performed by laboratories, particularly when the emphasis is on their standardization status and interchangeability of results. METHODS We used a panel of 20 fresh-frozen single-donation serum samples to assess assays for the measurement of creatinine, glucose, phosphate, uric acid, total cholesterol, HDL cholesterol, LDL cholesterol, and triglycerides. The commercial random access platforms included: Abbott Architect, Beckman Coulter AU, Ortho Vitros, Roche Cobas, Siemens Advia, and Thermo Scientific Konelab. The assessment was done at the peer group level and by comparison against the all-method trimmed mean or reference method values, where available. The considered quality indicators were intraassay imprecision, combined imprecision (including sample–matrix interference), bias, and total error. Fail/pass decisions were based on limits reflecting state-of-the-art performance, but also limits related to biological variation. RESULTS Most assays showed excellent peer performance attributes, except for HDL- and LDL cholesterol. Cases in which individual assays had biases exceeding the used limits were the Siemens Advia creatinine (−4.2%), Ortho Vitros phosphate (8.9%), Beckman Coulter AU triglycerides (5.4%), and Thermo Scientific Konelab uric acid (6.4%), which lead to considerable interassay discrepancies. Additionally, large laboratory effects were observed that caused interlaboratory differences of >30%. CONCLUSIONS The design of the EQA study was well suited for monitoring different quality attributes of assays performed in daily laboratory practice. There is a need for improvement, even for simple clinical chemistry analytes. In particular, the interchangeability of results remains jeopardized both by assay standardization issues and individual laboratory effects.
Summary The specific IgE antibodies were studied with the Phadebas® RAST technique in 35 patients with asthma due to diisocyanates. Two had been sensitized to toluene diisocyanate (TDI), 17 to methylene diisocyanate (MDI) and 16 to hexamethylene diisocyanate (HDI). In each case the diagnosis was confirmed with a bronchial provocation test (BPT). The asthmatic reaction was immediate in 17 cases, of which three had also a late reaction (dual). Eighteen patients reacted only with a late reaction. Seven (20%) had specific IgE to diisocyanates. All RAST‐positive patients had an immediate asthmatic reaction. None of the late reactors and referents had positive RASTs. RAST inhibition tests with 94–100% inhibition confirmed the specificity of the method. There was cross‐reactivity between different diisocyanates, however. The patients with positive RAST to diisocyanates had a higher level of total IgE than the RAST negative group and the referents.
We measured the IgG subclass antibody levels to wheat flour in 42 bakers and 20 controls with an enzyme immunoassay. The levels of total IgG, IgG1 IgG2 and IgG4 antibodies were significantly higher in the bakers than in the unexposed controls. The presence of anti-wheat flour IgG subclass antibodies in the bakers was correlated with various clinical variables including IgE levels, duration of asthmatic or rhinitis symptoms, skin prick test response, peripheral blood eosinophil levels, bronchial histamine reactivity and responses to nasal challenge with wheat flour. The IgG subclass antibody levels of the total cohort of bakers did not correlate with any of the measured clinical variables. However, among men specific IgG4 and IgG1 antibody levels correlated negatively with total IgE levels and duration of rhinitis, respectively. We conclude that IgG and IgG subclass levels to wheat flour in bakers reflect exposure, but that it is not related to any specific clinical situation. The exact pathogenic role of these antibodies in the development of occupational asthma and rhinitis is thus not clear.
Objectives-To assess the prevalence of enzyme sensitisation in the animal feed industry. Methods-A cross sectional study was conducted in four animal feed factories, where several enzymes had been used in powder form for 7-9 years. Before this study, enzymes in liquid form had started to be used. Sensitisation to enzymes was examined by skin prick and radioallergosorbent (RAST) tests. Altogether 218 workers were tested; 140 people in various tasks in manufacturing, where exposure to various organic dusts and to enzymes was possible, and 78 non-exposed oYce workers. The workers were interviewed for work related respiratory and skin symptoms. Total dust concentrations were measured by a gravimetric method. The concentrations of protease and -amylase were measured with catalytic methods and that of xylanase with an immunological method. Results-Ten workers (7%) were sensitised to enzymes in the exposed group of 140, whereas none were sensitised in the non-exposed group. Six of the sensitised people had respiratory symptoms at work: two of them especially in connection with exposure to enzymes. . On average, highest xylanase and -amylase concentrations were found in the various manufacturing sites, whereas the highest protease concentrations were found in areas of high total dust. Conclusions-Industrial enzymes may cause allergies in the animal feed industry. There is a need to assess exposure to enzymes at various phases of production, and to minimise exposures. (Occup Environ Med 2001;58:119-123)
We describe the assay conditions for an enzyme-linked immunoassay for the determination of IgG and IgG subclass antibodies in serum to water-soluble wheat flour antigens. The optimal antigen coating concentration was 5 micrograms/ml for total IgG, IgG1, IgG4 and 100 micrograms/ml for IgG2. Serial dilutions of test sera were used and commercially available monoclonal mouse anti-human IgG isotype antibodies (as ascites fluid) were diluted 1:500-1:1000. Specific wheat flour antibodies belonging to the IgG1, IgG2 and IgG4 subclasses were detected. Despite the lack of standardized isotype-specific second mouse monoclonal antibodies, the subclass antibody levels between flour-exposed bakers and controls could be compared. We observed significantly higher IgG1, IgG2, and IgG4 subclass antibodies among 23 bakers than among 12 non-exposed controls, but no IgG3 antibodies were detected. The differences in biological activities of the IgG subclass antibodies may explain the clinical and pathophysiological features for fluor-induced occupational allergic diseases among bakers.
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