A-115 Evaluation of Activated Aspartate Aminotransferase (A-AST) Assay using the Abbott Alinity c and Architect c4000

Abstract Background Aspartate Aminotransferase (AST) is an enzyme primarily found in hepatocytes. Elevated serum AST levels may indicate diseases such as hepatitis, mononucleosis, and alcohol cirrhosis. Activated AST (A-AST) includes pyridoxal-5’-phosphate (P5P), the active form of vitamin B6 as a cofactor, ensuring assay reliability even in patients with vitamin B6 deficiency. This study assessed the performance and clinical suitability of the A-AST assay using the Abbott Alinity c and Architect c4000 analyzers. Methods Method comparison (MC), linearity, precision, reference interval verification, and reagent carryover studies were conducted. MC was performed using residual patient serum or plasma samples (N=48). Additional MC studies were conducted with various subsets of these samples. Samples were analyzed on the Alinity and Architect analyzers using the A-AST assay and compared to the legacy AST assay not containing P5P. To investigate observed differences between legacy AST (non-International Federation of Clinical Chemistry and Laboratory Medicine standardized) and A-AST assays (IFCC-standardized), additional analysis was performed between two Abbott analyzers: Alinity and Architect. Additionally, the Alinity was compared to Roche ASTP (IFCC-standardized) using samples (N=25) on the cobas pro c503 analyzer, an assay which also contains P5P. An external MC with Multicare Health Systems was conducted with samples (N=10) using the A-AST assay on the Alinity. Linearity was evaluated using commercially available linearity material. Intra-assay precision was assessed with 10 replicates of commercially available control material in a single run. Inter-assay precision involved analyzing 5 replicates of each control per day, over 5 days (total 25 replicates). Reference interval verification was performed by collecting plasma from self-reported healthy volunteers (N=25; 12 males, 13 females). Reagent carryover was assessed on the Alinity between A-AST and open channel assays following the manufacturer*s operation manual. EP Evaluator was used for data analysis. Results MC showed slopes ranging from 1.13-1.25 with an average percent bias of 20.1% when comparing A-AST to the legacy AST assay. Comparisons between Alinity A-AST and Architect A-AST assays demonstrated a slope of 1.07 and percent bias of 8.1%. Comparisons between Abbott A-AST and Roche ASTP assays showed a slope of 1.08 and percent bias of 5.2%. Comparisons between ARUP A-AST and Multicare A-AST on Alinity showed a slope of 1.08 and percent bias of 5.4%. Overall, MC studies indicated an expected positive percent bias between Abbott legacy assays and IFCC-standardized assays which is likely attributable to the different formulations. Linearity studies demonstrated percent recoveries ranging from 91.9-101.1%. Precision analysis revealed within-run and total coefficient of variation <2.6%. The existing reference interval of 16-40 U/L was verified with 96% of results within the proposed interval. No reagent carryover was observed. Conclusion The Abbott A-AST assay demonstrated acceptable performance on the Alinity and Architect platforms. Differences observed for MC are likely due to varying formulations and standardizations of the A-AST assay compared to the legacy AST assay. The A-AST assay delivers dependable and precise results which are not impacted by vitamin B6 status, making it a valuable resource for the clinical diagnosis and monitoring of conditions linked to increased concentrations of AST.