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.
Villanueva et al. (Wed,) studied this question.
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