We read with great interest the study by Tome et al1 in which patients with microscopic colitis treated with bile acid sequestrants were identified in hospital registers and long-term efficacy assessed using retrospective data.

Several aspects of the response to treatment in the 282 patients included were unusual. Only 64% had responded to previous treatment with budesonide, which is lower than the 81% clinical response rate reported in clinical trials2 and a large-volume case series.3 This discrepancy probably is owing to a selection bias favoring budesonide nonresponders, as would be expected from the current study's design.1 Ninety patients were tested for bile acid diarrhea, of whom 51 (57% of the tested and 18% of the total cohort) had a positive test.