Is the Study Design Appropriate?

What is the appropriate study design?

Does this treatment work?

Systematic review or meta-analysis of trials; RCT

How good is a diagnostic test?

(Prospective) cohort study; systematic review of cohort studies

Should we screen?

RCT; systematic review of trials

What causes this disease?

RCT; prospective cohort study; case-control study (rare diseases); systematic review

What did people think or do?

Cohort study; cross-sectional survey; qualitative study Advice on whether a study is correctly termed prospective or retrospective can be found in this BMJ paper.

Suboptimal study designs include:

case series with no (or inadequate) control group. We will consider these if they are sufficiently informative and are compelling and well described. A suitable instance may be to describe early management of a major threat to public health.
retrospective study using casenotes, charts, or other routinely collected records in one or only a few hospital/general practice/doctor's office(s). We will consider these if the records were interrogated to answer a clear, predefined research question and the database included over 400 patients' details.
non-randomised trial of a comparison or intervention/uncontrolled intervention study. We may consider such an article, however, if it reports the evaluation of a quality improvement initiative where the rationale and process evaluation may have been more important than the outcomes; a large scale public health or health services intervention; or a "journalology"/peer review research study where randomisation was impossible.