Eligibility criteria

Item 14a: Eligibility criteria for participants

Example

“Patients should meet the following inclusion criteria: (1) KOA (knee osteoarthritis) according to the clinical American College of Rheumatology (ACR) criteria.[references] The clinical ACR criteria [reference] for KOA are: knee pain and at least three of the six following features: age ≥50, morning stiffness <30 min, crepitus, bony tenderness, bony enlargement, no palpable warmth. KOA will be confirmed with radiographs, including anterior-posterior and medio-lateral radiographs for imaging of the tibiofemoral joint, and an axial view for imaging of the patellofemoral joint. Patients with tibiofemoral (and patellofemoral) OA will be included. Kellgren and Lawrence (K&L) grading system for OA [references] will be applied, with K&L grade 2 or higher defined as OA; radiographic KOA is defined as definite osteophytes and possible joint space narrowing [references]; (2) pain, nominated by the patient as three or higher on a visual analogue scale on most days of the last 3 months [reference]; (3) aged ≥50 years.

Exclusion criteria are:

• Treatment with exercise therapy or joint infiltrations (eg, corticosteroids, hyaluronic acid) in the preceding 6 months.

• Being on a waiting list for knee replacement.

• Any contra-indication for exercise therapy as established by the treating physician.

• Corticosteroid infiltrations in the last 6 months.

• Cognitive impairment (unable to understand the test instructions and/or Mini-Mental State Examination score <23/30).

• Unable to understand the Dutch language.

• Inflammation unrelated to OA (eg, due to acute or chronic infection) established by CRP >10 mg/L.

• Presence of a disorder (eg, cancer, fibromyalgia, rheumatoid arthritis) and/or medication (eg, opioids, immunotherapy, anti-epileptics) that influences pain and/or the immune system" [205].

Explanation

The criteria for eligible participants in a trial are important, partly because they should reflect the aim of the trial, and partly because they affect recruitment, attrition, [206-212] outcome event rates, [213, 214] and generalisability [215]. 

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Typical selection criteria relate to the nature and stage of the condition or disease being studied, to the exclusion of persons thought to be particularly vulnerable to harm from study participation, and to issues required to ensure that the study satisfies legal and ethical norms.

Reviews of two samples of 108 and 292 trial protocols from 2016 found that patient eligibility criteria were reported in 100% of protocols [9, 10]. The importance of transparent documentation is highlighted by evidence that the eligibility criteria listed in published trials often differ from those specified in the trial protocol [216, 217] For example, a systematic review of articles comparing protocols and published reports (the vast majority being clinical trials or systematic reviews) found discrepancies regarding eligibility criteria in 25% to 57% of studies [64]. 

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Certain eligibility criteria may warrant explicit justification in the protocol, particularly when they limit the trial sample to a narrow subset of the population [215, 218]. The appropriateness of restrictive participant selection depends on the trial objectives [219]. When trial participants differ substantially from the relevant clinical population, the trial results may not easily be extrapolated to routine clinical settings [216, 220].

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Summary of key elements to address

• Specific inclusion and exclusion criteria defining the trial population to be randomised.