Editor,—We read with great interest the excellent guidelines for clinical trials in Helicobacter pyloriinfection published last September (Gut1997;41(suppl 2):S1–23). The recommendations almost without exception, are extremely useful. We feel, however, that one or to points might be expanded, or deserve extra comment.

As the working party states, most of the studies published on eradication therapy are non-comparative or are not large enough to reach a definite conclusion. This is because the sample size required to rule out a 10% difference between treatment groups for a two-branch comparative study is nearby 600 patients.1 To our knowledge no studies of this size have been published to date and, therefore, the length and composition of ideal eradication therapy has to be determined in large multicentre trials.

Inclusion criteria, initial evaluation, and …