Example

“Patients aged 18 years or older were recruited from 20 UK National Health Service (NHS) trusts. Patients were eligible if they had a diagnosis of shoulder pain attributable to a rotator cuff disorder (eg, cuff tendonitis, impingement syndrome, tendinopathy, or rotator cuff tear) that had started within the past 6 months. We used the diagnostic criteria set out in the British Elbow and Shoulder Society (BESS) guidelines. Patients were excluded if they had a history of significant shoulder trauma (eg, dislocation, fracture, or full-thickness tear requiring surgery), neurological disease affecting the shoulder, other shoulder conditions (eg, inflammatory arthritis, frozen shoulder, or glenohumeral joint instability), received corticosteroid injection or physiotherapy for shoulder pain in the past 6 months, or were being considered for surgery. Detailed criteria are in the protocol” [181].

 

Explanation

A comprehensive description of the eligibility criteria used to select the trial participants is needed to help readers interpret the study. In particular, all inclusion and exclusion criteria should be reported to judge to whom the results of a trial apply—that is, the trial’s generalisability (applicability) and relevance to clinical or public health practice (item 30) [179]. A description of the method of recruitment, such as by referral or self-selection (eg, through advertisements) is also important in this context. Because they are applied before randomisation, eligibility criteria do not affect the internal validity of a trial, but they are central to its external validity.

 

Typical and widely accepted selection criteria relate to the nature and stage of the condition or disease being studied, the exclusion of persons thought to be particularly vulnerable to harm from the study intervention, and to issues required to ensure that the study satisfies legal and ethical norms. The informed consent of study participants, for example, is typically required in intervention studies. Where relevant, it is important to describe whether sex and/or gender were taken into account in the design of the trial, including whether there was adequate representation of men and women (or diverse genders), and justify the reasons for any exclusion [182].

 

Despite their importance, eligibility criteria are often not reported adequately. For example, in an analysis of 283 reports of trials published between 1994 and 2006 in high impact general medical journals, reporting of exclusion criteria was often poor and incomplete: 84% of published trials contained at least one poorly justified exclusion criteria, and in 61% more than a quarter of the trial’s exclusion criteria were poorly justified [183]. Any differences in eligibility criteria between the trial protocol and final publication should also be highlighted and reasons for any discrepancies reported. A review of 52 protocols and 75 subsequent full publications submitted to a German medical ethics committee between 2000 and 2006 identified modifications to the eligibility criteria for 85% of trial publications, with 41% of final publications containing newly added criteria [184]. Similar deficiencies have been found in other studies [185, 186].