Comparison of Serum and Heparinized Plasma Samples for Measurement of Chemistry Analytes

Abstract

Twenty apparently healthy volunteers who had been fasting for 12–14 h had serum and lithium-heparin specimens collected in that standard draw order during a single venipuncture. All studies conducted with human samples were approved by the Institutional Review Board of the University of Utah. The samples were centrifuged, serum and plasma were separated from cells within 1 h of collection, and 1-mL aliquots were frozen within 2 h of collection and stored at −70 °C for up to 8 months. Before analysis, the aliquots were thawed and mixed well. Matched aliquots of serum and heparinized plasma were analyzed within 4 h of thawing. The serum samples were analyzed sequentially, followed immediately by sequential analysis of the heparin-plasma samples. Alanine aminotransferase, albumin, alkaline phosphatase, aspartate aminotransferase, calcium, carbon dioxide, chloride, cholesterol, creatinine, γ-glutamyltranspeptidase, glucose, LD, potassium, phosphorus, sodium, total bilirubin, total protein, urea nitrogen, and uric acid were analyzed on both a Roche Modular P analyzer and a Vitros 950 analyzer. Additional assays for aldolase, α₁-antitrypsin, amylase, angiotensin-converting enzyme (ACE), bile acids, direct bilirubin, ceruloplasmin, complement C4, complement C3, high-sensitivity C-reactive protein, creatine kinase, fructosamine, HDL-cholesterol, haptoglobin, iron, lipoprotein(a), lipase, LDL-cholesterol, magnesium, prealbumin, pancreatic amylase, phospholipids, transferrin, triglycerides, total iron-binding capacity, and unbound iron-binding capacity were performed only on the Roche Modular P analyzer. All reagents were from the instrument manufacturers unless otherwise stated in Table 1 of the Data Supplement that accompanies the online version of this letter at http://www.clinchem.org/content/vol50/issue9/.