Understanding Clinical Papers. David Bowers

      Second, it is usually difficult to select a wholly suitable control group for a case–control study. In a case–control study concerned with smoking and lung cancer, for example, should those without lung cancer be people with other cancers, or patients with other respiratory conditions, or other patients at the hospital without chest disorder, or general practice cases (and should they exclude those with chest problems), or members of the general public who are not drawn from healthcare contacts at all? None of these possible groups is wholly suited or unsuited; in the end, the findings will often be hard to interpret whichever control group is selected (sometimes case–control studies use more than one control group for just such reasons). Put another way, the control group in a case–control study is intended by the researcher to represent, as if it were a small random sample, the great many people in the population who have not developed the outcome. Unfortunately, in practice, they are instead a specifically targeted group – easily identified and included in the research – but not actually providing the representation of the non‐cases in the population that the researcher ideally wants.

      Cohort analytic studies avoid the worst aspects of the above two problems. First, because exposure is assessed at the start of the study, it is not subject to false remembering later. Second, assessment of exposure to risk often provides sensible exposed and unexposed groups, and avoids uncertainty over which comparison group to choose.

      Both these kinds of analytic observational study are greatly prone to confounding. This matter is discussed in Chapters 17, 34, and 35.

‘STROBE' GUIDELINES

      Readers of research want to know that the material in front of them is fairly and comprehensively described, preferably setting out what was planned, as well as what was done. We all hope that researchers will tell us in a thorough way what their question was, how the study planned to answer that question, how it was undertaken, what was found, and that they will give us a fair interpretation of what it all means – particularly in relation to the limitations of the design and its execution, and how generalizable the findings are likely to be. As a commendable attempt to render it more likely that we shall read research that attains these standards, people have been trying in recent years to set out guidance for the reporting of research. Researchers have got together with journal editors, and research funders and others, to draw up guidelines that are endorsed by journals as a standard of excellence for reporting. The best‐known guidelines, and the first to be widely adopted by journals and researchers, are the CONSORT guidelines for the reporting of clinical trials, discussed in the next chapter. The guidelines of interest for reporting observational analytic studies are the STROBE guidelines: STROBE stands for STrengthening the Reporting of OBservational studies in Epidemiology . The guidance covers what should be set out in cohort analytic studies, case–control studies and analytic cross‐sectional studies. Clinical research papers will sometimes allude to conformity with the STROBE guidelines and, in general, where they do so the account should adequately cover all of the components referred to above. Some journals will insist that all authors apply the guidelines and submit a checklist of the items; the checklist is not usually published but is used by the peer reviewers and editors.