The stability of 65 biochemistry analytes in plasma, serum, and whole blood.

OBJECTIVES: The pre-analytical stability of various biochemical analytes requires careful consideration, as it can lead to the release of erroneous laboratory results. There is currently significant variability in the literature regarding the pre-analytical stability of various analytes. The aim of this study was to determine the pre-analytical stability of 65 analytes in whole blood, serum and plasma using a standardized approach. METHODS: Blood samples were collected from 30 healthy volunteers (10 volunteers per analyte) into five vacutainers; either SST, Li-heparin, K2-EDTA, or Na-fluoride/K-oxalate. Several conditions were tested, including delayed centrifugation with storage of whole blood at room temperature (RT) for 8 h, delayed centrifugation with storage of whole blood at RT or 4 °C for 24 h, and immediate centrifugation with storage of plasma or serum at RT for 24 h. Percent deviation (% PD) from baseline was calculated for each analyte and compared to the maximum permissible instability (MPI) derived from intra- and inter-individual biological variation. RESULTS: The majority of the analytes evaluated remained stable across all vacutainer types, temperatures, and timepoints tested. Glucose, potassium, and aspartate aminotransferase, among others, were significantly impacted by delayed centrifugation, having been found to be unstable in whole blood specimens stored at room temperature for 8 h. CONCLUSIONS: The data presented provides insight into the pre-analytical variables that impact the stability of routine biochemical analytes. This study may help to reduce the frequency of erroneous laboratory results released due to exceeded stability and reduce unnecessary repeat phlebotomy for analytes that remain stable despite delayed processing.

Evaluation of a New NT-proBNP Immunoassay on an Automated Core Laboratory System.

BACKGROUND: Heart failure remains a major cause of morbidity and mortality despite improvements in treatment. This study aimed to evaluate the Alere N-terminal pro B-type natriuretic peptide (NT-proBNP) immunoassay on the Abbott Alinity i platform. METHODS: The analytical performance including precision, linearity, limit of quantitation (LOQ), carryover, dilution-recovery, and stability was evaluated. A method comparison between the Abbott Alere NT-proBNP assay and Roche Elecsys proBNP II assay was performed using 70 residual plasma samples. RESULTS: Total imprecision was 4.1%, 3.5%, and 2.3% for low (120.9 ng/L), medium (333.9 ng/L), and high (4767.4 ng/L) QC levels, respectively. The manufacturer's claimed LOQ of 8.3 ng/L was verified. Method comparison between the Alere NT-proBNP assay and the Elecsys proBNP II assay showed good agreement between assays with an R value of 0.998, a slope of 1.05 (95% CI, 1.03-1.06), and an intercept of 45.81 (95% CI, -46.6.84 to 138.22). The Bland-Altman plot showed an absolute bias of 250 ng/L or 6.02%. Subrange analysis (NT-proBNP <2000 ng/L) showed good agreement with an R value of 0.998, a slope of 1.04 (95% CI, 1.02-1.06), and an intercept of -4.83 (95% CI, -26.95 to 17.28), with a mean bias of 26 ng/L or 3.2%. The stability of NT-proBNP was also verified in lithium heparin plasma samples stored at 4°C over a 7-day period. Hemolysis and lipemia interference thresholds were verified, but icterus impacted NT-proBNP recovery by >20% at low analyte concentrations. CONCLUSIONS: The Alere NT-proBNP assay demonstrated acceptable analytical performance and very good clinical concordance with the Elecsys proBNP II assay.