A Rapid Approach for Assessing Body Fluid Matrix Effects

While clinical laboratories routinely perform automated chemistry assays on approved specimens (e.g., plasma and serum), the FDA has not evaluated the validity of these assays for nonapproved specimens (e.g., various body fluids). To meet College of American Pathologists' regulatory requirements, clinical laboratories must evaluate body fluid matrix effects. However, full validation studies are challenging due to time and labor demands. Therefore, a rapid and practical approach for validating body fluids benefits clinical laboratories by improving efficiency and minimizing resources utilized.

Excess body fluids and plasma specimens were collected and frozen until testing was performed. Pooled body fluid specimens were spiked with a 10% spike solution (pooled plasma) containing analyte mixtures with measured concentrations. Matrix interference studies and dilution studies were performed on the Roche cobas automated (6000/8000) analyzers.

The matrix effects for albumin, amylase, blood urea nitrogen, cholesterol, creatinine, glucose, lactate, lactate dehydrogenase, lipase, potassium, sodium, total bilirubin, total protein, triglycerides, and uric acid were all within acceptable limits (±20% of full recovery). However, lipase was observed to be unstable in peritoneal fluid. Dilution linearity was confirmed for all analytes in pleural, peritoneal, ascites, and synovial fluids (R2 > 0.90).

Our study describes a rapid and practical approach for evaluating body fluid matrix effects in automated clinical chemistry assays. By streamlining the validation process, this approach can help laboratories maintain compliance while minimizing time and resources.