A validation study of selected methods routinely used for measurement of cyclosporine.

We compare four methods for measuring cyclosporine (CyA) in plasma and whole blood of transplant patients: HPLC, RIA with a polyclonal antibody, RIA with a monoclonal antibody, and fluorescence polarization immunoassay (FPIA). The monoclonal RIA procedure correlated acceptably with HPLC, with slope = 1.21, r = 0.97, and Sy,x = +/- 40.1. However, the FPIA, done in three separate instruments, correlated relatively poorly with HPLC, giving slopes of 1.67, 1.51, and 2.32; correlation coefficients of 0.72, 0.43, and 0.83; and Sy,x = +/- 205.4, +/- 334.5, and +/- 222.4. The polyclonal RIA correlated reasonably well with HPLC, with a slope = 1.15, r = 0.90, and Sy,x = +/- 72.6. Values for individual patients with increases both in gamma-glutamyltransferase and creatinine showed very poor correlation between FPIA and HPLC, which suggests that metabolite cross-reactivity with FPIA is significant and unpredictable in patients with liver dysfunction coexisting with renal dysfunction. Evidently, the monoclonal RIA can be substituted for HPLC, if the therapeutic range is adjusted for the 21% higher results obtained by RIA.

Pitted keratolysis: a manifestation of human dermatophilosis.

A case of pitted keratolysis caused by Dermatophilus congolensis is reported. The organism was isolated from the lesion and identified by its morphological, cultural, and biochemical characteristics. A survey of the literature revealed that it rarely causes human infections, but is a common causative agent of disease in domesticated and wild animals. Human infections reported previously were traced to contact with infected animals or contaminated soil. We report pitted keratolysis in a 44-year-old physician with no known history of such a contact.

Measurements of serum gentamycin levels by rapid tests.

Gentamicin is a very useful antimicrobial agent for the treatment of serious infections caused by gram-negative bacteria. However, it's low therapeutic index and potential ototoxic and nephrotoxic side effects necessitate frequent determinations of serum concentration to assist in maintaining therapeutic levels and avoiding toxic levels. Two bioassays and a latex agglutination inhibition card (LAIC) test were evaluated to determine gentamicin levels in nearly 100 patient sera. Results were compared with a radioimmunoassay (RIA). Two bioassays, the Bio-Monitor and the GentaSak, gave correlation coefficients of 0.987 and 0.982, respectively. The correlation coefficient for the LAIC test was 0.987. All three tests compared well with RIA in accurately detecting gentamicin levels in patients as well as simulated sera. The LAIC test, however, was more rapid, giving results within half an hour whereas bioassays required 6--8 hours for completion. The LAIC test was also found to be more economical. It provides a suitable alternative to RIA procedures in small laboratories and for performing 'stat' tests since batching is not necessary.

Comparison of spot esculin hydrolysis with the PathoTec strip test for rapid differentiation of anaerobic bacteria.

The ability of several anaerobic bacteria to hydrolyze esculin to esculetin is used by clinical microbiologists and taxonomists in the differentiation and identification of both gram-positive and gram-negative microorganisms. Conventional methods used for determining esculin hydrolysis by anaerobic bacteria require 24 to 48 h for completion. In this paper we evaluate two procedures which yield rapid results. A total of 738 anaerobic bacteria were used in this study. A total of 99% of the esculin-hydrolyzing anaerobic bacteria gave positive results with the spot test in 1 h, whereas the other test method, the PathoTec strip test (General Diagnostics, Morris Plains, N.J.), required 4 h for 96% of the strains tested to yield positive reactions. Both tests showed a 100% specificity when compared with the standard broth test and are easy to perform, accurate, and economical. The spot test is superior to the PathoTec strip test in yielding results more rapidly.

Evaluation of three methods for the measurement of urea nitrogen in serum as used on six instruments.

The authors compared three urea nitrogen methods using six instruments: (1) the diacetyl monoxime method used with a continuous flow analyzer Sequential Multiple Analyzer Model 4 + 2; (2) the diacetyl monoxime method used with an older continuous flow analyzer (Sequential Multiple Analyzer Model 6/60; (3) the diacetyl monoxime method used with a third continuous flow system, AutoAnalyzer Model I; (4) the urease-conductivity method performed on the Beckman System I; (5) the urease-glutamate dehydrogenase method performed on the DuPont Automatic Clinical Analyzer; (6) the urease-glutamate dehydrogenase method done on a centrifugal analyzer, CentrifiChem. We evaluated each method for the following: (1) within-run precision; (2) between-day precision; (3) linearity of the relationship between concentration and instrument output; (4) specificity; (5) carry-over; (6) comparison of urea nitrogen values for samples from patients.

The use of "clear" enzyme control materials.

Low turbidity, "clear" enzyme controls commercially produced in three concentrations and conventional human lyophilized control sera, which are more turbid, were evaluated to determine which was superior for quality control purposes. Criteria used to evaluate the controls were: 1) turbidity measurement, 2) daily assays for 30 days to estimate day-to-day precision, and 3) stability of the enzyme assay value for these controls when they were reconstituted and frozen for 0 to 30 days and 0 to 10 days with three aliquots separately prepared and frozen for 0 to 10 days for a total of 30 days. The controls were analyzed for lactate dehydrogenase, alanine aminotransferase, aspartate aminotransferase, creatine kinase, and alkaline phosphatase activities with the Perkin-Elmer KA 150 enzyme analyzer.

Clinical laboratory evaluation of the Perkin-Elmer KA-150 Enzyme Analyzer.

We evaluated the Perkin-Elmer KA-150 Enzyme Analyzer in a clinical laboratory situation according to a rigid evaluation protocol. The factors evaluated for five commonly assayed enzymes were as follows: (a) rate of analysis of patient samples, (b) analytical linearity, (c) overall precision (within-run and between-day), (d) carry-over from a sample with activity near 1000 U/liter, (e) error detection at low and high concentrations, (f) correlation of values with those obtained by methods used in our laboratory and (g) normal-value ranges. We find the KA-150 to be an effective and rapid enzyme analyzer.

Measurement of spectral bandwidth, as exemplified with the Beckman "Enzyme Analyzer System TR spectrophotometer".

This paper describes simple methods for determining spectral bandwidth by measurement and by calculation. We measured the spectral bandwidth of the monochromator from the Beckman Enzyme Analyzer TR, and found it to be 3.5-4.0 nm (av 3.8) by two different methods. We visually estimated it to be 4 nm. Using the specifications for the diffraction grafting, focal length, and fixed slit width, we calculated the theoretical spectral bandwidth to be 3.6 nm.

Evaluation of the Beckman "System TR enzyme Analyzer".

We evaluated 16 claims made by Beckman Instruments, Inc. for its Enzyme Analyzer (System TR), under a rigid written protocol for the Product Evaluation Subcommittee of the Standards Committee of the College of American Pathologists. We found the following to be within the company's specifications: (a) accuracy and precision of the temperature control; (b) accuracy and precision of the sample and reagent pipets; (c) instrument precision, both within-run and between-day; (d) carry-over from a sample with activity greater than 1000 U/liter; (e) instrument-to-instrument variation; (f) analytical linearity; (g) analysis time; (h) correlation of the instrument-printed answer with the activity calculated manually from a strip-chart recorder; (i) precision of the instrument's built-in electronic "standard"; (j) effectiveness of the over-range indicators; and (k) correlation between results of these enzyme assay methods and those for kinetic methods used in our laboratory. The instrument performed well.