Journal of the International Federation of Clinical Chemistry最新文献

The method-dependency of measurements of enzyme activity presents problems of interpretation and comparison. Enzyme calibration materials may provide results in agreed-upon units of catalytic concentration while allowing a choice of routine methods. However, this requires the calibrating and calibrated methods to be equally specific, close agreement in intermethod ratio to exist between the calibrator and target enzyme in serum, and absence of significant sample-dependent variation in the intermethod ratio.

Six recommendations on the theory, production, and use of reference values have been prepared by the IFCC's Expert Panel on Theory of Reference Values. This review serves as a guide to the documents and presents the main topics.

External proficiency testing is a proven method for improving the quality of laboratory measurements, including lead in blood. Several proficiency testing programs exist to fill this need. This article describes the U.S. federally sponsored Blood Lead Proficiency Testing Program. Three specimens, composed of blood from dosed cows, are distributed to participants each month. Target values are determined by a group of 10 referee laboratories. Participant performance has shown steady improvement over time.

The term commutability applied to reference materials denotes the ability of the material to show interassay changes comparable to those observed in the measurement of the same analyte in human serum. In this study commutability was studied by first establishing the relationship between the results obtained on patient serum samples with two independent methods for a given analyte. Then, the calibration or control material was assayed with the same pair of methods, and its interassay bias was statistically compared with that shown by patient sera. The results obtained in 27 experiments showed that the frequencies of noncommutability in the measurement of some nonenzymic organic components, enzymes, and inorganic ions were, respectively, 25/83, 44/99, and 32/61. The impact of noncommutability of the materials on the results of external quality assessment schemes (EQAS), matrix interferences, and the behavior of particular components are considered. The conclusion drawn is that each material should be tested for commutability before it is used as a reference material.

The invention of the polymerase chain reaction (PCR) technique for nucleic acid amplification has had a major impact on many diverse areas of both basic and clinical research. Since its inception in 1985, reports on a wide variety of applications for PCR have received much attention in scientific and medical literature. This technology has been shown to have wide applicability to the diagnosis of human disease, including such diverse areas as infectious diseases, genetic disorders, and cancer. This article presents a broad overview of the principles of PCR including generic concerns that must be addressed when using or designing PCR-based assays. The application of PCR-based assays for the diagnosis of genetic disorders and for infectious disease testing is also discussed.

Determination of the quantity and activity of the Protein C molecule is of the utmost importance in highly purified concentrates prepared for replacement therapy. A multicenter study was undertaken to evaluate the comparability and accuracy of Protein C assays from commercial sources. Significant between-assay and interlaboratory differences were found for both functional and immunological assays. The interlaboratory variability is explained in part by the use of different control plasmas. The results also indicate the importance of the diluent used. This study emphasizes the need for standardized methods for determining the characteristics of Protein C concentrates.

The authors provide the results of a short-term experimental trial in external quality assessment in 42 clinical laboratories conducted by the Mexican Ministry of Health. Assay kits for glucose, urea, and creatinine were prepared by the Ministry. The results may prove useful to organizers of external quality assessments in third-world countries who may opt for this strategy to improve performance. The laboratories performed the tests on reconstituted lyophilized control serum, also prepared by the Ministry. All three assays were performed manually using colorimetric methods. On the basis of their intralaboratory precision (coefficients of variation less than 8%, 8-12%, and greater than 12% for high, medium, and low precision, respectively), 12 laboratories demonstrated high precision for all three tests. Eight laboratories showed medium and low precision for different tests, while the other 22 fell in between. The results showed that the strategy of using centrally prepared reagents to improve interlaboratory agreement did not work well for urea and creatinine, but met expectations for glucose. The laboratories achieved an interlaboratory coefficient of variation of 10% for glucose in this first trial.