Estimation of the minimal preanalytical uncertainty for 15 clinical chemistry serum analytes

Abstract

BACKGROUND: We sought a model to estimate preanalytical uncertainty of blood samples collected and processed by using optimal procedures. METHODS: Optimal preanalytical handling of blood samples included use of a loosely fastened tourniquet, wide bore needles, recommended clotting time and centrifugation speed, and minimal storage before analysis. Blood was collected from each arm of 20 volunteers into 2 rapid-serum tubes and 2 serum-separation tubes. Linear mixed-effects models were used to estimate the between-venipuncture SD, the preanalytical SD (excluding venipuncture), the measurement repeatability SD, and systematic differences between the tubes and between venipunctures. RESULTS: No significant systematic differences were found between successive venipunctures. However, statistically significant mean differences were seen between serum-separation tubes and rapid-serum tubes for 7 of the 15 analytes. The preanalytical SD (excluding venipuncture) for lactate dehydrogenase (3.2 U/L, 95% CI 2.8 -3.7) was significantly higher than the SD for measurement repeatability (1.9 U/L, 95% CI 1.7-2.1). For potassium both the preanalytical SD (excluding venipuncture) (0.092 mmol/L, 95% CI 0.080 - 0.11) and the between-venipuncture SD (0.075 mmol/L, 95% CI 0.048 - 0.12) were significantly higher than the measurement-repeatability SD (0.031 mmol/L, 95% CI 0.028 - 0.035). For glucose the between-venipuncture SD (0.20 mmol/L, 95% CI 0.14 - 0.27) was significantly higher than the preanalytical SD (excluding venipuncture) (0.07 mmol/L, 95% CI 0.06 - 0.08), and the measurement repeatability SD (0.057 mmol/L, 95% CI 0.051- 0.064). CONCLUSIONS: By applying linear mixed-effects models we have estimated the minimal preanalytical uncertainty that will influence all patient results. © 2010 American Association for Clinical Chemistry.