Real-world experience with the diagnosis of bile acid malabsorption (BAM) using serum 7-alpha-C4 and 48-hour stool bile acids

Abstract

Introduction and aims

Bile acid malabsorption (BAM) is responsible for 30% of cases of diarrhea-predominant irritable bowel syndrome (IBS-D) or functional diarrhea and 63.5% of cases of diarrhea following cholecystectomy. ⁷⁵SeHCAT is the gold standard diagnostic method but is unavailable in Mexico. Alternatively, primary bile acid (PBA) and total bile acid (TBA) determination in 48 h stools and 7αC4 measurement have been proposed as screening tests.

Objective

Our aim was to evaluate the experience with PBAs and/or TBAs and to determine whether 7αC4 is a good screening biomarker for BAM in clinical practice.

Material and methods

An ambispective study of patients with chronic diarrhea was conducted. BAM was considered present with 7αC4 > 55 ng/mL (cost $420.00 USD), PBAs ≥ 9.8%, TBAs > 2,337 μmol/48 h, or TBAs > 1,000 μmol/48 h + PBAs > 4% (TBAs + PBAs) ($405.00 USD). However, those tests must be shipped to the US for their analysis (total cost $825.00 USD). Data were compared using the chi-square test and Student’s t test, and Spearman’s Rho correlations were calculated.

Results

We analyzed 48 patients with 7αC4 (age: 58.4 ± 16.9, women: 54.2%). BAM was confirmed by 7αC4 in 12.5%, by PBAs in 38.9%; by TBAs in 5.5%, and by TBAs + PBAs in 16.7%. We found elevated 7αC4 in patients with high or normal PBA/TBA levels (correlation with TBAs: 0.542, p = 0.020; PBAs: -0.127, p = 0.605; TBAs + PBAs: -0.200, p = 0.426). Lastly, BAM identified by 7αC4 was more frequent in patients with previous cholecystectomy (22.7%) vs. those without (3.8%).

Conclusions

Our study confirms that 7αC4 correlates well with TBAs and is a good biomarker for BAM screening because it can be elevated, despite normal PBA/TBA levels. Additionally, it represents a 49% cost savings in BAM investigation.