There are now many evidence based clinical guidelines and good systematic reviews, some of which may relate directly to your article. We would like you, therefore, to provide suitable evidence for key statements - the Cochrane Library or a medical librarian should be able to help you.

Guidelines
Try to indicate probabilities and levels of evidence:

• Frequency information: when giving a differential diagnosis for a particular presentation please provide population estimates of the frequency of each separate diagnosis
• Diagnostic tests: please give their false positive and false negative rates (or sensitivities and specificities) and, if possible, the causes of false positives and false negatives
• Prognosis: information on prognosis or natural history is often missing from medical articles but is vital for rational decision making. Wherever possible, give information about remission, progression and risks of disease
• Treatments: please mention the level of evidence on which main treatment recommendations are made. This can be kept relatively simple, using three levels:

• No clear evidence: opinions based on clinical experience, anecdotal case studies, or descriptive articles; conflicting evidence from studies or poorly designed studies, even if randomised controlled trials
• Suggestive evidence: evidence from cohort, case control, before-and-after studies; evidence from non-randomised experimental studies
• Firm evidence: evidence from at least one properly designed randomised, controlled trial with adequate sample selection, sample size, and appropriate controls; with double or single blinding; and with clear outcome(s)

Please try to quantify the benefit of treatment, giving the relative risk reduction or the typical number needed to treat.