Amniotic fluid gamma-glutamyl transferase for prediction of biliary atresia in cases of non-visualisation of the fetal gallbladder: a retrospective study using a validated analytical platform and local reference range

Introduction:The level of amniotic fluid gammaglutamyl transferase (AFGGT) may help identify biliary atresia (BA) in cases of non-visualisation of the fetal gallbladder (NVFGB).This study aimed to validate a serum/plasma matrix-based gammaglutamyl transferase (GGT) assay for amniotic fluid (AF) samples, establish a local gestational age-specific AFGGT reference range, and evaluate the efficacy of AFGGT for predicting fetal BA in pregnancies with NVFGB using the constructed reference range. Methods:The analytical performance of a serum/ plasma matrix-based GGT assay on AF samples was evaluated using a Cobas c502 analyser.Amniotic fluid gamma-glutamyl transferase levels in confirmed euploid singleton pregnancies (16 +0 to 22 +6 weeks of gestation) were determined using the same analyser to establish a local gestational age-specific reference range (the 2.5th to 97.5th percentiles).This local reference range was used to determine the positive predictive value (PPV) and negative predictive value (NPV) of AFGGT level <2.5th percentile for identifying fetal BA in euploid pregnancies with NVFGB. Results:The serum/plasma matrix-based GGT assay was able to reliably and accurately determine GGT levels in AF samples.Using the constructed local gestational age-specific AFGGT reference range, the NPV and PPV of AFGGT level <2.5th percentile for predicting fetal BA in pregnancies with NVFGB were 100% and 25% (95% confidence interval=0, 53), respectively.