Imprecision of cardiac marker analyses among laboratories on the basis of external quality assurance results: Finnish experience.

The purpose of this report was to evaluate the reproducibility and harmonization of cardiac marker tests and to describe the current situation concerning quality of assays for cardiac markers on the basis of the results of the external quality control schemes (EQAS) of Labquality Ltd., Helsinki, Finland in the period 2002 to 2005. Finnish EQAS surveys obtained for proficiency samples at low marker concentration indicated that the overall coefficient of variation (CV) between laboratories for CK-MBmass and troponin I exceeded 10 %, while for cardiac troponin T the CV was 8.6 %. Intra-laboratory reproducibility was investigated in a single laboratory using concomitant testing in the same EDTA plasma samples to establish cut-off limits for one CK-MBmass and three troponin assays. The 10 % imprecision limit obtained from the concomitant testing in the same samples for CK-MBmass was (by Elecsys) 8.5 microg/L, for cardiac troponin T (by Elecsys) 0.023 microg/L and for cardiac troponin I (by AxSYM) and by Immulite 2000) 0.85 microg/L and 0.63 microg/L. At present, it is recommended that laboratories determine the concentration at which the 10 % imprecision for a specific cardiac marker assay is reached, because the assays generally do not reach that imprecision at the level of the 99th percentile value, usually taken as decisional level. However, common efforts of scientific societies and professional diagnostic industry associations internationally are needed if consensus is to be reached on standardization of immunoassays for cardiac markers and uniform results obtained among laboratories.

Best use of the recommended IFCC reference method, material and values in HbA1C analyses.

The results of Finnish HbA(1C) surveys (Labquality Ltd.) during the past 10 years have undergone continuous improvement with smaller overall coefficients of variation for the HbA(1C) mean values of all methods (from 7.5 to 5.4% for normal and from 8.9 to 4.7% for diabetic samples). Most of the HbA(1C) methods are certified for traceability to the Diabetes Control and Complication Trial (DCCT) designated comparison method, which originally was a high-performance liquid chromatography (HPLC) method (Bio-Rex 70, Bio-Rad) but is no longer in routine use. It was therefore important that the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) had prepared both reference preparations and method for the determination of HbA(1C). However, the very demanding reference method is not realistic for use in clinical laboratories. According to the present study, the mean HbA(1C) values of the Labquality Ltd. showed significant correlations to the HbA(1C) values of The European Reference Laboratory for Glycohemoglobin (r = 0.999) and to the values using the IFCC method (r = 0.999). The reference values of the IFCC method (mainly those of the manufacturer) range from 2.85 to 3.81%, being significantly lower than the present DCCT values (4.0-6.1%). Since it may take some time before consumers are ready to accept the new IFCC reference values for general use, we propose that the IFCC reference materials and method should be used for calibration of the present methods to the well-known DCCT levels.

Problematic determination of serum growth hormone: experience from external quality assurance surveys 1998-2003.

The objective of the present study was to start a new external quality assurance survey (EQAS) for the determination of serum growth hormone (GH) using pooled serum specimens as quality-assurance samples. To give good coverage of multiple forms of GH, the specimens included sera from GH-deficient and acromegalic patients as well as from persons showing a normal response in GH provocation tests. In one survey the quality-control specimens were spiked with exogenous 22-kD GH to obtain some idea of the specificity and GH recovery of the assays. The EQA surveys of 1998-2003 were organized by Labquality of Helsinki in cooperation with three university hospital laboratories in Finland. The number of participating laboratories ranged from 8 to 14. During 1998-2003, gratifying methodological harmonization occurred in the participating group, as the participants switched to the immunometric detection principle, the number of method applications decreasing from 7 to 3. In 1998 the 14 participating laboratories reported five different conversion factors (from microg/l to mU/l), whereas in 2003 7 of the 8 participants reported the same factor. Despite the harmonization trend among participating laboratories, further efforts are needed, because marked method-based differences still exist. This dialogue should include kit manufacturers, laboratory experts, EQA organizations and clinicians using the test results.

Sensitisation to enzymes in the animal feed industry.

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 office 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 alpha-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. Enzyme concentrations in the air varied greatly: xylanase from less than 0.8 ng/m(3) up to 16 ng/m(3), alpha-amylase from less than 20 ng/m(3) up to 200 ng/m(3), and protease from less than 0.4 ng/m(3)up to 2900 ng/m(3). On average, highest xylanase and alpha-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.

Risk of enzyme allergy in the detergent industry.

OBJECTIVES: To assess the prevalence of enzyme sensitisation in the detergent industry. METHODS: A cross sectional study was conducted in a detergent factory. Sensitisation to enzymes was examined by skin prick and radioallergosorbent (RAST) tests. 76 Workers were tested; 40 in manufacturing, packing, and maintenance, and 36 non-exposed people in management and sales departments. The workers were interviewed for work related respiratory and skin symptoms. Total dust concentrations were measured by a gravimetric method, and the concentration of protease in air by a catalytic method. RESULTS: Nine workers (22%) were sensitised to enzymes in the exposed group of 40, whereas none were sensitised in the non-exposed group. All the sensitised people had symptoms at work; all had rhinitis and one had asthma. Protease concentrations were generally < 20 ng/m3, but occasional peak values up to 80 ng/m3 were detected in the packing and maintenance tasks, and high values of > 1 microgram/m3 in the mixing area. CONCLUSION: Despite the use of encapsulated enzyme preparations, high enzyme concentrations in workplace air are possible, resulting in a higher risk of sensitisation than expected.

Subclasses of IgG anticardiolipin antibodies in patients with systemic lupus erythematosus.

Antibodies directed to a co-factor associated with negatively charged phospholipids, such as cardiolipin, occur in patients with systemic lupus erythematosus (SLE), and possibly more often in those with venous or arterial thrombosis, thrombocytopenia or recurrent fetal loss. They are also found in patients without any of these manifestations and their biological effect, if any, might thus be related to their IgG subclass. To investigate this possibility, we determined anticardiolipin antibodies (ACA) by enzyme immunoassay (EIA) using monoclonal antibodies (MoAb) against human IgG subclasses. A net absorbance of x +3 SD of the value of 30 blood donors was taken as the cut-off point. The specificity of the assay was verified through inhibition experiments using cardiolipin micelles. Thirty-three patients with SLE were studied, all of whom had been shown to have ACA by a point dilution screening assay. IgG1 ACA were found in 85% of the patients, and ACA of the IgG2, IgG3 and IgG4 subclasses in 42%, 39% and 15%. There was a significant correlation between the presence of IgG3 ACA and of anti-DNA antibodies but none between subclass distribution and major clinical manifestations of SLE.

Clinical significance of IgG subclass antibodies to wheat flour antigens in bakers.

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.

Determination of IgG subclass antibodies against wheat flour antigens by an ELISA technique.

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.

Experiences of specific IgE in asthma due to diisocyanates.

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.