Wiener klinische Wochenschrift. Supplementum最新文献

Serum cortisol is one of the more frequently requested steroid hormone assays. Its use is important in evaluating diseases of the adrenal cortex and pituitary. We briefly review the biochemistry of cortisol synthesis, the pathophysiology resulting from adrenal and pituitary abnormalities and the more specific immunochemical procedures which have replaced colorimetric chemical assays for cortisol. We also report our results on the evaluation of the analytical performance of the non-isotopic homogeneous CEDIA Cortisol assay and compare the advantages of this assay to state-of-the-art immunoassays.

We present the results of a multicentre evaluation with Boehringer Mannheim/Hitachi instruments of new "enzymatic" methods for the determination of Na+, K+, and Cl- in serum or plasma. The between-day coefficient of variation was less than 1.4% (Na+), less than 2.6% (K+) and less than 1.7% (Cl-). The linear range of the assays were at least 80 to 200 mmol/l (Na+), 1.5 to 17 mmol/l (K+) and about 30 to at least 200 mmol/l (Cl-). The comparisons with routine flame atomic emission spectrometry and coulometry showed a satisfactory agreement of the test results. The "enzymatic" assays are insensitive to even grossly elevated levels of bilirubin and lipids (sodium, potassium, and chloride assays), NH4+ (potassium assay) and amylase (chloride assay). Interference by various drugs was not detected. Since the new methods can easily be adapted to photometric clinical chemistry instruments, they represent a valuable alternative to the use of ion-selective electrodes, flame atomic emission spectrometry and coulometry.

We evaluated a CEDIA assay for the determination of digitoxin in serum on random access analyzers. The multicenter evaluation included studies on the analytical range, calibration stability and reproducibility of the new assay. Moreover, recovery in controls, transferability of results obtained in different laboratories, comparability with routine methods, and the effect of various interfering factors have been analyzed. Summarized the analytical performance was comparable to that of routine methods. The CEDIA Digitoxin assay represents an attractive alternative to established digitoxin immunoassays because it can be performed on random access analyzers, thus permitting the simultaneous determination of digitoxin and other serum analytes without sample splitting.

New homogeneous enzyme immunoassays have been developed for cortisol, digoxin, digitoxin, theophylline, phenytoin, and phenobarbital using the cloned enzyme donor immunoassay technology. As applied to Boehringer Mannheim/Hitachi analysis systems these methods provide rapid, accurate and precise quantification of analytes, with minimal interferences from endogenous serum constituents and low cross-reactivities to structurally-related hormonal precursors, drug metabolites and natural compounds. Additional significant features of the new assays are linear standard curves and two-point calibration. The six CEDIA assays join the two currently available CEDIA assays for determination of the thyroid parameters T4 and T Uptake. Additional new therapeutic drug and anemia monitoring assays are under development, demonstrating the versatility of the cloned enzyme donor immunoassay technology. These tests, in concert with Boehringer Mannheim/Hitachi analyzers, provide a high throughput, random access immunoassay system. The menu of available assays should continue to increase during the 1990s, providing efficient automation while allowing consolidation of testing on a limited number of instrument systems.

Some aspects of a new homogeneous enzyme immunoassay for the determination of digoxin have been evaluated, as part of a multicenter project. The CEDIA Digoxin assay is based on the use of two beta-galactosidase fragments (EC 3.2.1.23) produced by recombinant DNA techniques, one of them linked to digoxin. These two fragments couple to form the complete active enzyme, if not hindered by anti-digoxin antibodies. Digoxin in serum competes for antibody binding. The procedure can easily be automated and does not require special equipment. The imprecision of the method was studied at three different concentration levels (0.56, 1.29 and 2.77 ng/mL of digoxin). Within-run coefficients of variation were 8.01%, 5.57% and 3.30%, respectively, the corresponding between-day CVs being 17.4%, 8.41% and 4.89%. The procedure was found to be linear up to 4.4 ng/mL. Reagents were stable for at least four weeks. Results obtained by the CEDIA Digoxin assay compared well with those obtained by fluorescence polarization immunoassay.