PubMed · 10292749
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M S Lifshitz, R P De Cresce. Du Pont Dimension.. https://pubmed.ncbi.nlm.nih.gov/10292749/
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Direct HDL-cholesterol (HDLc) assays have several advantages over other assays that are more laborious and time-consuming. A recent College of American Pathologists (CAP) report indicates that at least 385 Beckman LX-20 analyzers use the selective detergent (homogeneous or direct) method for analyzing HDLc. There is no published evaluation of direct HDLc assays on the Beckman platform. Here we report our evaluation of a direct HDLc assay marketed by Beckman for the Beckman LX-20 analyzers. In general, the assay performed well; however, the total error was not within National Cholesterol Education Program (NCEP) guidelines. This was largely because of a significant positive bias that appeared to be due, at least in part, to triglycerides. This bias was worse at HDLc concentrations <40 mg/dL, which may make it difficult to identify a low HDLc concentration and consequently an increased risk for cardiovascular disease (CVD).
BACKGROUND: Erythropoietin (EPO) is a glycoprotein hormone produced by specialized cells in the kidney that acts as the primary regulator of erythropoiesis. Serum EPO measurements are useful for diagnostic evaluations of anemia and polycythemia. METHODS: The IMMULITE 2000 is an automated random access immunoassay analyzer for the central laboratory. The limit of detection (LOD), linearity, imprecision, comparison to another commercially available assay, and reference interval of a new EPO assay for this analyzer were assessed. RESULTS: The LOD was 0.2 U/l. The assay was linear within an allowable systematic error of 10% over the range tested (2-178 U/l). The total imprecision of the new assay was <7% for concentrations from 15.8 to 68.4 U/l. Comparison with the Advantage EPO assay method showed comparable results. Deming regression analysis gave a slope of 1.13+/-0.02, an intercept of -1.09+/-0.97, and a S(y/x) of 7.1 (r=0.99) over the range tested (2-200 U/l). CONCLUSIONS: The IMMULITE 2000 EPO assay shows acceptable performance and is suitable for routine clinical use.
UNLABELLED: The literature about salivary lactate dehydrogenase (LDH) activity shows different results, conditioned by the diversity of methods used for sampling, handling and analysis. OBJECTIVES: The aim of this study was to design a protocol for quantifying salivary lactate dehydrogenase activity. METHODS: Whole saliva samples were collected from 100 healthy volunteers by chewing a roll of cotton. Lactate dehydrogenase activity determinations were made with the Cobas Mira Plus II autoanalyser using the recommendations proposed by the International Federation of Clinical Chemistry (IFCC) and the French Society of Clinical Biology (SFBC). Samples were stored at room temperature (20-22 degrees C), in the refrigerator (4 degrees C) and freezer (-20 degrees C). The correction capacity of the autoanalyser was evaluated by making serial determinations in samples of saliva diluted in water. RESULTS: The frozen samples, but not those stored in the refrigerator or at room temperature, showed an important degradation of lactate dehydrogenase activity. When the samples were diluted in water, the lactate dehydrogenase activity varied substantially with the International Federation of Clinical Chemistry method after correction, but not when using the French Society of Clinical Biology method. CONCLUSION: For salivary lactate dehydrogenase activity quantification we suggest that samples be stored at 4 degrees C and analyse with the French Society of Clinical Biology method.