SERUM 7-ALPHA-HYDROXY-4-CHOLESTEN-3-ONE AND SELENOHOMOCHOLYLTAURINE (SEHCAT) WHOLE-BODY RETENTION IN THE ASSESSMENT OF BILE-ACID INDUCED DIARRHEA

Objective: To assess the reliability of serum 7 alpha-hydroxy-4-choles ten-3-one (7 alpha-3ox-C) in the differential diagnosis of bile acid i nduced diarrhoea by comparison with (75)selenohomocholyltaurine whole body retention (SeHCAT WBR). Design: One hundred and sixty-four patien ts with chronic diarrhoea were investigated prospectively in two centr es (Edinburgh and Sweden) by two different tests which measure bile ac id loss or synthesis: the SeHCAT test which measures the 7-day SeHCAT WBR and serum 7 alpha-3ox-C which reflects the rate of bile acid synth esis. Results: Forty-six patients had SeHCAT WBR of less than 10% (19 with ileal disease or resection, nine with idiopathic bile acid induce d diarrhoea and 18 with miscellaneous causes for bile acid induced dia rrhoea). All patients with ileal or idiopathic disease showed a favour able response to treatment as did 13 of the miscellaneous group. Serum 7 alpha-30x-C was raised in all subjects with ileal disease/resection , seven patients with idiopathic disease and all subjects in the misce llaneous group who responded to treatment. Sixteen out of 118 patients with SeHCAT WBR greater than or equal to 10% had raised serum 7 alpha -3ox-C. Conclusion: The positive predictive value of serum 7 alpha-30x -C was 74%. The high negative predictive value (98%) of serum 7 alpha- 3ox-C indicates the possible use of this test for excluding bile acid malabsorption in this population. All but two subjects who responded t o treatment had raised serum 7 alpha-30x-C concentrations. The possibi lity that the sensitivity of the test can be improved by repeat testin g needs to be further investigated. There was a significant correlatio n between fractional catabolic rate (FCR) SeHCAT and serum 7 alpha-3ox -C (r=0.63, P<0.0001). Further data are required to validate the refer ence range in women over 70 years of age.