Appraisal of Analytes in the Laboratory Panels for Liver Function Tests: Do we Need Aspartate Aminotransferase and Direct Bilirubin in the Panels? Running Head: AST and Direct Bilirubin in Lab Panels

Background: The Centers for Medicaid and Medicare Services approved a number of panels as screening tests including those for liver functions. The utility of routinely testing for Aspartate aminotransferase (AST) and direct bilirubin was questioned and empirical data analyzed to suggest alternatives. Methods: Tests done over six months were examined for AST, ALT, total and direct bilirubin values. Panels in which AST exceeded the ALT value by 40 units or more and the AST/ALT ratio was 2.0 or greater, were subjected to review of medical records. The incidence of elevated direct bilirubin at various levels of total bilirubin was assessed. Results: 2.9% of the AST and ALT tests involving 379 patients met the criteria of AST ≥ ALT by 40 units and AST/ALT 2.0. Alcohol use/abuse was the primary reason for the AST-ALT abnormality in only 49.3% of the patients. AST-ALT levels and ratio were useful in revealing alcohol abuse in perhaps one patient. Bilirubin results revealed that direct bilirubin was elevated in only 0.4% of the samples if the total bilirubin was <0.9 mg/dL. Conclusions: AST determinations do not add meaningful information about liver function and removing this analyte from the panels will not materially affect the usefulness of results. Testing for direct bilirubin should be changed to reflex testing only if total bilirubin is ≥ 0.9 mg/dL. Not performing AST and direct bilirubin routinely has the potential of saving >$92 MM/year.