Background: The INVESTIGATE-I study was designed to inform a future definitive randomised trial of invasive urodynamic testing, compared to basic clinical assessment with noninvasive tests prior to surgical treatment, in women with stress urinary incontinence or stress-predominant mixed urinary incontinence. In a pilot randomised controlled trial, women from seven participating sites were screened, consented and randomised. Overall, 771 patients were identified from clinic notes and correspondence as being potential recruits and were sent the Patient Information Leaflet. Of those screened, 284 were deemed eligible, giving an overall 'screen positive' rate of 37 %. The numbers screened at individual centres varied between 14 and 399; the 'screen positive' rate varied between 22 and 79 % and the percentage of eligible women recruited varied between 55 and 100 %. The aim of this additional substudy was to explore why 'screen positive' rates may have varied so widely between apparently similar sites.
Results: All 11 trial staff involved in screening in the seven recruiting sites were asked to evaluate a series of 20 identical vignettes, mainly based on actual general practitioner referral letters. Of the vignettes, 16 mentioned one or more definite inclusion criteria; the remainder had possible inclusions. Four had definite exclusions; 12 had possible exclusions. Free-text comments were sought to clarify the screeners' decisions. For six vignettes everyone agreed that the patient was eligible; for one all agreed she was not eligible; the breakdown for the remainder was mixed. Free-text comments illuminated uncertainties that may have led to variability in judging potential eligibility.
Conclusions: Variability in judgements about potential trial eligibility highlights the importance of explicit and objective inclusion and exclusion criteria, and of agreed strategies for making judgements when information is missing. During the development and planning of trials, vignettes might be a valuable tool for training those involved in screening and recruiting patients, for identifying potential problems and ensuring greater consistency in the application of eligibility criteria.
Trial registration: ISTCTN registry: ISRCTN71327395 , registered on 7 June 2010.
Keywords: Eligibility; Equipoise; Randomised controlled trial; Recruitment; Screening; Stress urinary incontinence; Surgery; Urodynamic investigation; Vignette.