Controlled trials in gastrodyspepsia: a methodological aspect.

Non-ulcer dyspepsia (NUD) is a poorly defined condition that is not very suitable for conventional randomised double-blind studies. A multi cross-over model (MCO-model) has been designed allowing identification of individual drug responders with a defined degree of certainty. The model involves regular interchanges between periods with active drug and placebo, and the evaluation is based on the number of times the active drug is associated with fewer symptoms than the preceding or following placebo period (X-score). A drug responder may be defined by a certain minimum value for the X-score. The risk of being wrong may then be easily calculated from the probability distribution of the X-score. The effect of cimetidine in patients with NUD has been studied using a variant of the MCO-model including 6 treatment periods of 2 or 4 days' duration. So far, the conclusion that the MCO-model is able to identify individual cimetidine responders among patients with NUD appears to be justified. The preliminary findings furthermore suggest that cimetidine responders among patients with NUD are characterised rather by symptoms suggestive of reflux esophagitis than by hypersecretion of acid.