ClinicalTrials.gov registration can supplement information in abstracts for systematic reviews: a comparison study

Abstract

BackgroundThe inclusion of randomized controlled trials (RCTs) reported in conference abstracts in systematic reviews is controversial, partly because study design information and risk of bias is often not fully reported in the abstract. The Association for Research in Vision and Ophthalmology (ARVO) requires trial registration of abstracts submitted for their annual conference as of 2007. Our goal was to assess the feasibility of obtaining study design information critical to systematic reviews, but not typically included in conference abstracts, from the trial registration record.MethodsWe reviewed all conference abstracts presented at the ARVO meetings from 2007 through 2009, and identified 496 RCTs; 154 had a single matching registration record in ClinicalTrials.gov. Two individuals independently extracted information from the abstract and the ClinicalTrials.gov record, including study design, sample size, inclusion criteria, masking, interventions, outcomes, funder, and investigator name and contact information. Discrepancies were resolved by consensus. We assessed the frequencies of reporting variables appearing in the abstract and the trial register and assessed agreement of information reported in both sources.ResultsWe found a substantial amount of study design information in the ClinicalTrials.gov record that was unavailable in the corresponding conference abstract, including eligibility criteria associated with gender (83%; 128/154); masking or blinding of study participants (53%, 82/154), persons administering treatment (30%, 46/154), and persons measuring the outcomes (40%, 61/154)); and number of study centers (58%; 90/154). Only 34% (52/154) of abstracts explicitly described a primary outcome, but a primary outcome was included in the “Primary Outcome” field in the ClinicalTrials.gov record for 82% (126/154) of studies. One or more study interventions were reported in each abstract, but agreed exactly with those reported in ClinicalTrials.gov only slightly more than half the time (88/154, 56%). We found no contact information for study investigators in the abstract, but this information was available in less than one quarter of ClinicalTrial.gov records (17%; 26/154).ConclusionRCT design information not reported in conference abstracts is often available in the corresponding ClinicalTrials.gov registration record. Sometimes there is conflicting information reported in the two sources and further contact with the trial investigators may still be required.

Reporting Weaknesses in Conference Abstracts of Diagnostic Accuracy Studies in Ophthalmology

“…8 A previous evaluation of the content of abstracts of randomized trials presented at the ARVO Annual Meeting also found important study design information frequently unreported. 9 However, the authors concluded that missing information was often available in the corresponding ClinicalTrials.gov record. Because diagnostic accuracy studies are rarely registered, 10 complete reporting of conference abstracts is even more critical for these studies.…”

How should systematic reviewers handle conference abstracts? A view from the trenches

“…Inclusion of conference abstracts in this searchable database means searching for conference abstracts is less resourceintensive than in the past. Second, largely driven by their brevity, abstracts may not contain adequate information for systematic reviewers to appraise the design, methods, risk of bias, outcomes, and results of studies reported in the abstracts [18][19][20][21]. Third, the dependability of results presented in abstracts also is questionable [22][23][24], which occurs at least in part because (1) most abstracts are not peer-reviewed and (2) results reported in abstracts are often preliminary and/or based on limited analyses conducted in a rush to meet conference deadlines.…”

Radiological and clinical outcomes of novel Ti/PEEK combined spinal fusion cages: a systematic review and preclinical evaluation

“…Conversely, the limited information on study design in abstracts makes it difficult to evaluate the validity of study methodology and results, although minimized if CON-SORT guidelines for conference abstract reporting are adopted [31].…”