Results with six "kit" radioimmunoassays for primary bile acids in human serum intercompared

Area of Science:

• Biochemistry
• Clinical Chemistry
• Immunology

Background:

• Accurate measurement of primary bile acids in human serum is crucial for diagnosing liver diseases.
• Radioimmunoassay (RIA) is a common method, but various labeled isotopes (e.g., 3H, 125I) exist, necessitating comparative studies.

Purpose of the Study:

• To evaluate and compare the performance of six different radioimmunoassay procedures for quantifying primary bile acids (cholic acid and chenodeoxycholic acid) in human serum.
• To assess the accuracy, precision, stability, and analytical recovery of both 3H-labeled and 125I-labeled RIA kits.

Main Methods:

• Six RIA kits were analyzed: two using 3H-labeled antibodies and four using 125I-labeled antibodies.
• Serum samples from 80 healthy subjects were analyzed to determine normal ranges for conjugated chenodeoxycholic acid and cholic acid.
• Correlation analyses were performed to compare results between different assays and between individual bile acids and their sum.

Main Results:

• A significant correlation (p < 0.01) was found between assays for both cholic acid and chenodeoxycholic acid across varying serum concentrations.
• All tested kits met acceptable standards for accuracy, precision, stability, and analytical recovery.
• Normal ranges established were 0.4–2.5 mumol/L for conjugated chenodeoxycholic acid and 0.3–1.5 mumol/L for conjugated cholic acid.

Conclusions:

• All six radioimmunoassay procedures are suitable for measuring primary bile acids in human serum, offering comparable results.
• While 125I-labeled assays offer convenience by not requiring liquid-scintillation equipment, they may slightly reduce antibody affinity.
• The assays are sufficiently sensitive for detecting bile acid levels in both healthy individuals and patients with liver disease.