Automated Biochemical Analysis of Pericardial Fluid: Validation of the Assays for Lactate Dehydrogenase, Total Protein, Albumin, Amylase, Urea Nitrogen, Cholesterol, Direct and Total Bilirubin, and Lactate on an Automated Chemistry Analyzer.

BACKGROUND: Biochemical analysis of pericardial fluid (PF) can aid in the determination of the etiology of pericardial effusions. We validated 9 assays for albumin, amylase, blood urea nitrogen, cholesterol, direct and total bilirubin, lactate, lactate dehydrogenase, and total protein on the Roche Cobas c702 analyzer for PF. METHODS: For each analyte, a recovery study was conducted to assess the effect of matrix; intra- and interassay precisions were determined at 3 levels; linearity was evaluated using 5 concentrations across the analytical measurement range; common interferences of hemoglobin, bilirubin, and triglycerides were investigated; and the stability at 22°C up to 7 days, 2°C to 8°C up to 14 days, and -20°C up to 4 weeks was studied. RESULTS: For all analytes, the recoveries were within 90% to 110%; the coefficient of variation ranged from 0% to 6% for intraassay and 1.1% to 6.9% for interassay precision. All assays exhibited linear response; the slopes ranged from 0.99 to 1.008, and R2 ranged from 0.999 to 1.000. No significant interferences of hemoglobin, bilirubin, or lipids were observed for all analytes except for direct bilirubin, which was negatively affected by hemoglobin and lipids. At -20°C, all analytes were stable for 4 weeks. At 2°C to 8°C, all were stable for 14 days except lactate dehydrogenase (2 days) and direct bilirubin (2 days). At 22°C, all were stable for 7 days except for direct bilirubin (8 hours) and total bilirubin (3 days). CONCLUSION: No matrix effects were observed with the assays for these 9 analytes in PF on the Cobas c702 analyzer.