B-024 Validation of an open-channel assay for measuring serum total bile acid (TBA) using the Cobas® Pro analyzer

Abstract Background Blood total bile acids (TBA) levels are routinely used for identifying and monitoring intrahepatic cholestasis of pregnancy (ICP). ICP is characterized by disrupted biliary flow causing bile acids to accumulate in circulation which can have consequences on both maternal and fetal outcomes. As such, TBA levels are crucial for appropriate management of patients with ICP and timely results are of particular importance at our institution with a focus on high-risk pregnancy patients. This study aimed to validate an open-channel assay for blood TBA on the cobas® c 503 analyzer following Clinical Laboratory Standards Institute (CLSI) recommendations. Methods The analytical performance of a TBA open-channel assay (Aviva Systems Biology) on the cobas® c 503 analyzer was assessed. Assay parameters were established based on Roche recommendations for converting cobas® c 502 – where TBA was previously being tested on – open-channel parameters to the c 503 analyzer. The validation consisted of precision, correlation, linearity, and dilutional recovery studies using a total allowable error of 10%. The data were visualized using Microsoft Excel and analyzed according to CLSI recommendations. Results Total imprecision of the assay was <2% across both manufacturer quality control materials. Correlation with patient samples (n = 40) against the c502 TBA assay was excellent (R2 = 0.9969) across a concentration range of 1 – 108 µmol/L.The assay demonstrated excellent linearity across the manufacturer stated analytical measurement range (1 – 100 µmol/L) and we were able to extend the measuring range up to 500 µmol/L through verifying acceptable recovery for 1:5 on-board dilutions. Conclusion Using a conversion system to migrate assay parameters from the cobas® c502 to c503 analyzer, we established a TBA assay that demonstrated excellent analytical performance with respect to precision, correlation, linearity, and dilutional recovery.