Urinary choloyl-PABA excretion in diagnosing small intestinal bacterial overgrowth - Evaluation of a new noninvasive method

The synthetic substrate cholyl-PABA, developed by conjugating cholic acid w ith paraamino-benzoic acid, is hydrolyzed by the bacterial enzyme cholyl hy drolase to release free PABA. This study aimed to evaluate whether quantita ting urinary excretion of PABA after oral administration of cholyl-PABA can detect small intestinal bacterial overgrowth. in the first phase, investig ations were performed on 10 healthy Volunteers to study the dynamics of uri nary excretion of PABA and any adverse reactions after oral administration of 1.2 g of cholyl-PABA. Another 10 healthy volunteers and 25 adult patient s with various gastrointestinal disorders participated in the second phase, where the urinary cholyl-PABA test was compared to the [C-14]xylose breath test (XBT). The upper limit of normal levels of urinary PABA excretion at the end of 4 h was 1.1% of the administered dose of cholyl-PABA. The urinar y PABA excretion after 4 hr [median (range), in percentage] in the XBT-posi tive group was 1.6 (0.6-35.0), which was significantly higher than those in the XBT-negative group [0.7 (0.4-1.8)] and the healthy controls [0.7 (0.2- 1.1)]. The agreement between the XBT and the urinary cholyl-PABA test was 8 5.7% (P < 0.01). No adverse effect was noted. In conclusion. the urinary ch olyl-PABA test offers a simple, safe, noninvasive, and rapid method for dia gnosing small intestinal bacterial overgrowth and warrants further clinical evaluation.