Serum TBA and GCA Levels Across Pregnancy and the Gestational Age-Specific Reference Intervals for Pregnant Chinese.

Background: Reference intervals of clinical laboratory indexes are the basis of interpretation of test results. While intrahepatic cholestasis of pregnancy (ICP) could severely threaten maternal and fetal health, reference intervals of the biomarkers serum total bile acids (TBA) and glycocholic acid (GCA) are unsatisfactory. The purpose of this study was to derive gestational age-specific reference intervals for serum TBA and GCA in a Chinese population to promote early diagnosis of ICP.

Methods: A total of 416 healthy pregnant Chinese were recruited and divided into three groups by gestational age: 140 in the first trimester (1 - 13 weeks) group, 136 in the second trimester (14 - 27 weeks) group, and 140 in the third trimester (≥ 28 weeks) group. Serum TBA and GCA levels were measured respectively by cyclic enzymatic method and latex enhanced immune turbidimetry. Reference intervals were calculated with non-parametric method.

Results: The reference intervals of serum TBA are 0.90 - 6.60 μmol/L, 1.20 - 9.10 μmol/L, and 1.50 - 8.90 μmol/L respectively in the first, second, and third trimester. The reference intervals of serum GCA are 0.24 - 1.14 μg/mL in the first and second trimesters (combined) and 0.00 - 2.04 μg/mL in the third trimester.

Conclusions: Gestational age-specific reference intervals of serum TBA and GCA for pregnant Chinese were derived in strict accordance with CLSI C28-A3 guidelines, which will be valuable for early diagnosis of ICP.