Biomedical subjects
Publications and source records attributed to T H Schwartz.
Changes in serum biochemical values as a function of serum-clot contact time were investigated. Time extending to 48 hours were studied by drawing sets of six specimens from ten subjects. Glucose, lactic dehydrogenase, the transaminases, potassium, alkaline phosphatase, and iron showed significant changes. Other common tests, including electrophoretic separations, were not affected.
Changes in serum chemistry values as a result of incomplete removal of erythrocytes and in vitro hemolysis during the preparative process have been studied. Two levels of contamination, corresponding to removal of 99% and 99.9% of the erythrocytes, were used to examine the effects of both hemolyzed and intact cells. Forty chemical procedures and methods were considered. Serum LDH values were most strongly affected by hemolyzed erythrocytes. Potassium, creatine phosphokinase, aspartate aminotransferase, alanine aminotransferase, and iron showed smaller but significant effects due to the presence of 1% hemolyzed cells, with lesser effects observed at the 0.1% level. The presence of non-hemolyzed cells at either level did not significantly alter chemistry results.
An integral blood-drawing-serum separator tube, (SST) is evaluated for use as an in-laboratory serum storage device. Sera stored in the SST were compared with paired controls that were specimens from the same subjects stored in closed culture tubes. Eighty-six serum chemistry determinations showed no clinically significant change as a result of 48 hours of storage in the original blood-drawing tubes. Storage of serum in this manner provides the laboratory with specimens for reanalysis or additional analyses while eliminating manipulative steps, including serum removal, tube relabeling, and intertube transfers, and reducing errors due to misidentification and/or contamination.
We have evaluated a serum separator device that is designed to effect better separation and isolation of serum from clotted blood. This device consists of an evacuated blood-drawing tube (Vacutainer) containing 1.5 ml of a semi-solid silicon polymer that forms a barrier between serum and clot during centrifugation. We compared test specimens with conventionally processed (Vacutainer) specimens as controls. Eighty-one chemical, toxicological, and immunological reactions, tests, or methods were studied. For several tests we observed changes that are statistically but not clinically significant. The one clinically significant change in serum chemistry values occurred in the case of lactate dehydrogenase, for which values were increased by 5-8% of the upper limit of normal.
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A blind quality control system using a special type of commercial reference serum is described. As packaged, the product contains six pools of analyzed reference sera with vials identified by coded numbers. The test constituents in the pools cover the range of multichannel analyzers in a random manner, i.e., each pool contains constituents in the low, normal and elevated ranges. As specific pools are not identified, and the analyst is unaware of the expected values for each constituent, results collected for quality control purposes are unbiased, i.e., free of conscious or unconscious editing. Data analysis in the proposed system is by least-squares technics. During an eight-week period, performance was studied using the standard error of the estimate to evaluate precision and the slope of the regression line to evaluate accuracy on the SMA and Mark X instruments. As an empirical comparison, the data are expressed as relative errors and precision and accuracy of analyzer performance evaluated as mean and standard deviation. The proposed regression analysis-based technic has the advantage of simultaneously evaluating linearity, as well as checking accuracy and precision over the total dynamic range of the instrument by use of a series of related serum pools.