The authors produced a systematic assessment list to evaluate the papers selected for the review. Studies were assessed for: prospective follow-up, stated aim, choice of sample size, source of patient sample, inclusion/exclusion criteria, use of appropriate control, randomisation, description of method of randomisation, more than one examiner for direct clinical evaluations, examiner calibration, report on patient loss, follow-up, and report on whether protocol deviation had occurred. The authors do not state how the papers were assessed for validity, or how many of the authors performed the validity assessment.