Cholylglycine determination by an automated chemiluminescence immunoassay: preliminary results in the intrahepatic cholestasis of pregnancy

Abstract

Background: One of the most frequent reasons to determine total bile acids (TBA) in a routine laboratory is for the diagnosis and management of intrahepatic cholestasis of pregnancy (ICP). The analytical methods that can be carried out for TBA determination are enzymatic and immunometric methods. However, the enzymatic methods suffer of significant cross-reactivity with ursodeoxycholic acid (UDCA), the principal drug administered in the ICP management. The aim of this paper is to evaluate the clinical utility of a new fully-automated chemiluminescence immunoassay (CLIA) to measure cholylglycine (CG) in the ICP. Methods: Two cohorts of patients with a singleton pregnancy, in the third trimester, were retrospectively recruited. The first cohort (controls, n=56, 21–48 years) was represented by patient hospitalized, for a different reason respect to ICP. The second cohort (ICP women, n=32, 22–45 years) was composed of women with a final diagnosis of ICP, before the treatment with UDCA. Results: Intra-assay and intra-laboratory imprecisions were less than 6%. The 95% CI of CG in the control cohort were 0.9–9.1 µmol/L. The levels of CG in the ICP women cohort ranged from 2.3 to 57.4 µmol/L. The optimal cut-off of CG for ICP was 5.5 µmol/L (sensitivity of 84% and specificity of 92%). Conclusions: CG determination by CLIA method has demonstrated a reliability from the analytical point of view. The obtained diagnostic accuracy for ICP was similar to the traditional assays carried out for TBA determination. Moreover, the turnaround time of CG analysis allows a rapidly answer to clinical suspects of cholestasis in pregnancies ensuring the patient-foetus safety.