The present paper describes a multicentre evaluation of a one step enzyme-immunoassay for the determination of cortisol in serum or plasma. Data from the investigation were analysed in terms of imprecision, detection limit, and correlation with other test methods.Within-run and between-run imprecisions (coefficient of variation) of Enzymun-Test(R) Cortisol were less than 8% and 12%, respectively. The detection limit was 30 nmol/l (11-mu-g/l). With the exception of prednisolone, only low interference was found with other endogenous steroids. A good correlation between Enzymun-Test(R) Cortisol and HPLC, LIA, FPIA and RIA was registered, although the latter two methods showed a scattering of regression lines from the different evaluators.The results show that Enzymun-Test(R) Cortisol can be recommended as an alternative for the measurement of cortisol. As the method is calibrated against isotope dilution-mass spectrometry, results obtained with Enzymun-Test(R) Cortisol are in agreement with the reference method.

This enzyme immunoassay (EIA) of human prolactin (hPRL) involves incubation of sample and anti-hPRL antibodies conjugated to horseradish peroxidase (EC 1.11.1.7) in tubes coated with a second antibody to hPRL. The test can be performed within 60 min. No reaction of the antibodies with human placental lactogen and human somatotropin is detectable. The presence of detergent allows assay of both serum and plasma. Precision was improved by including polyethylene glycol in the reaction mixture. To optimize analytical recovery, we added protease inhibitor. Assay of the EIA standards shows good correlation with results for World Health Organization reference preparations. The measurable range is 1 to 400 micrograms/L. Intra- and interassay CVs are about 5%. Comparisons with two RIAs and two other EIAs show reasonably good correlations. The components of our EIA are stable for 18 months.

The ES 600 sample-selective multibatch analyser was subjected to a multicentre evaluation in six laboratories in accordance with ECCLS guide-lines. During the 3-month trial, five Enzymun-Test diagnostics (T4, TBG, Digoxin, CEA and TSH)1) were measured at 25 degrees C. The study yielded the following results: 1. The within-series and between-series precision were very good, with mean CV's of approx. 3% and 7% respectively. 2. Recovery of the target values for three control sera was in the range +/- 5%. 3. A trend in measurements did not occur in any of the methods investigated (for series of over 240 determinations). 4. Comparison of the results with those obtained on the ES 22 Enzymun-Test system showed good agreement. 5. Within the measuring range defined by the standards, no deviations could be ascertained upon dilution of the samples. 6. Total carry-over in the instrument was below 0.05%. From studies with instruments from the first production series, it became evident that modifications were necessary to improve the reliability. A follow-up measuring programme confirmed a clear improvement in reliability and a reduction in the imprecision, particularly for results from series to series.