Analyte Concentrations In Plasma Research Articles

Effect of transport conditions on the stability of biochemical markers in blood.

We examined the stability of lipids, carotenoids, alpha-tocopherol, and endogenous hormones in plasma prepared from whole blood that had been mailed to a central location for processing. Initially, to simulate transport conditions, whole-blood samples were stored in the laboratory, either at room temperature or cooled, for up to 72 h before processing. In the latter samples, lipid concentrations changed up to 1.4% per day, carotenoids up to -5.5%, and hormones up to 9.5%. In a second study, analyte concentrations in plasma from cooled whole blood mailed via overnight courier were compared with those from plasma that had been immediately separated, frozen, and mailed via overnight courier. Concentrations of cholesterol, high-density lipoprotein subfraction 3, apolipoprotein B, and retinol were stable. Overall, for each marker except estradiol, the between-person variation was at least twice the within-person variation. In a third study, at least 340 micrograms of DNA was recovered from 30 mL of cool-shipped whole blood. Our results indicate that shipping whole-blood samples by overnight courier is feasible for assay of several biochemical markers of interest in epidemiological research.

A Comparison of Results for Serum Versus Heparinized Plasma for 30 Common Analytes

Twenty paired serum and heparinized plasma samples were assayed for 30 common analytes in order to determine whether medically significant differences exist at high and low decision levels. Linear-regression analysis was used to determine total systematic error and to predict analyte concentrations in plasma at decision levels. The predicted value was compared with criteria for medically allowable error in order to determine the validity of substituting heparinized plasma for serum. There were statistically significant and predictable differences between heparinized plasma and serum for assays of ammonia, ionized calcium, potassium, and amylase. There was marked bias and proportional error for alanine aminotransferase, γglutamyltransferase, lactate dehydrogenase, and aspartate aminotransferase. Transferase interference was method-dependent, and findings were not consistent with the recommendation provided in the manufacturer's method description. Serious analytical errors are likely if heparinized plasma is substituted for serum without study in the user's own laboratory.

Effect of heparin and citrate on measured concentrations of various analytes in plasma.

Frequently it is assumed that concentrations of biochemical analytes are similar for serum and plasma, without regard to the anticoagulant. Recently it has been hypothesized that use of certain anticoagulants results in an osmotic redistribution of fluid between blood cells and plasma, causing some dilution of the plasma. We sought to determine the effect of two commonly used anticoagulants, heparin and citrate, on the measured concentrations of 13 clinical-chemical analytes, including selected trace elements, vitamins, lipids, and proteins. The data demonstrate that hyperosmolar citrate causes a significant dilution of all indices measured. In contrast, heparin had no osmotic effect; concentrations of most of the analytes measured in the heparinized plasma were statistically no different from those measured in the corresponding serum. Therefore, anticoagulants must be chosen carefully, especially if concentrations in plasma and serum are to be compared.