36 Analytical Validation of Key Biochemical Analytes in Pericardial Fluid: Bridging the Gap in Clinical Diagnostics

Background Pericardial effusion occurs when there is excessive fluid accumulation in the pericardium, which may result from various medical conditions, including infections, autoimmune diseases, malignancies, injuries, and kidney failure. Pericardiocentesis is performed to drain the excess fluid, relieve pressure, and prevent cardiac tamponade. The analysis of specific biomarkers in pericardial fluid aids in diagnosing the underlying causes of fluid build-up. However, pericardial fluid is not currently an approved specimen type for any tests available on an automated chemistry analyzer. This study aims to validate the analysis of nine analytes including total protein, albumin, total bilirubin, direct bilirubin, cholesterol, amylase, lactate dehydrogenase (LDH), blood urea nitrogen (BUN), and lactic acid in pericardial fluid to establish their analytical performance and determine their clinical utilities. Methods Residual pericardial samples obtained for cytology analysis were used in this study to validate the analytical performance of nine biochemical analytes on the Roche Cobas c701 analyzer (Roche Diagnostics, Inc.). Key parameters included in the validation study were recovery, precision, stability, analytical measurement range (AMR), clinical reportable range (CRR), and common interferences. Samples for the recovery study were prepared by spiking pericardial fluid with a known concentration of an analyte in a ratio of no less than 9:1 (volume of pericardial fluid to volume of serum), ensuring that more than 90% of the mixture was pericardial fluid. Intra-day and inter-day precision studies were performed at medical decision limits or various concentrations. Linearity will be determined using serial dilutions of a sample containing a high concentration of an analyte. Stability studies will be performed using aliquots of a sample stored at room temperature, refrigerated, and frozen for various lengths of time. The interferences of hemolysis, icterus, and lipemia on the nine tests in pericardial fluid samples will be studied by adding hemolysate, bilirubin, and triglycerides to pericardial fluid. Results Preliminary data from the recovery studies demonstrated that the analytical method produced accurate and valid results, with reliable analyte recovery within acceptable limits (90–110%) for all nine analytes at four different levels. Intra-assay and inter-assay precision studies for total protein, albumin, total bilirubin, and direct bilirubin at three different levels met the acceptance criteria, with a coefficient of variation (CV) of less than 10%. Conclusion This study addresses a significant gap in laboratory medicine by validating key analytes in pericardial fluid. Completing the validation assessment, including linearity, precision and the other studies, will pave the way for establishing reliable clinical cutoff for these analytes or their serum-to-fluid ratios. These clinical cutoffs are essential for accurate clinical interpretation, improved diagnostic precision, and enhanced patient care. Furthermore, laboratory workflows for body fluid handling, developed based on the study results, will support greater standardization and efficiency in clinical laboratories.