Article type
Year
Abstract
Background: Many diagnostic accuracy studies are never reported in full in a peer-reviewed journal. Searching for unpublished studies may avoid bias due to selective publication, enrich the power of systematic reviews, and thereby help to reduce research waste.
Objectives: To assess searching practices among recent systematic reviews of diagnostic accuracy, with a special focus on the identification and inclusion of unpublished studies.
Methods: We included systematic reviews if they had evaluated the diagnostic accuracy of one or more index tests against a reference standard in humans. We extracted data from 100 non-Cochrane systematic reviews of diagnostic accuracy indexed in MEDLINE and published between 10-2017 and 01-2018, and from all 100 Cochrane systematic reviews of diagnostic accuracy published by 12-2018, irrespective of whether meta-analysis had been performed.
Results: Non-Cochrane and Cochrane reviews searched a median of 4 (IQR 3-5) and 6 (IQR 5-9) databases, respectively; most often MEDLINE/PubMed (n=100 and n=100) and EMBASE (n=81 and n=100). No language restrictions were applied in 37 and 90 reviews, and efforts to contact authors in case of incomplete or unclear data were announced or reported by 31 and 78 reviews. Additional efforts to identify studies beyond searching bibliographic databases were performed in 76 and 98 reviews, most often through screening reference lists (n=71 and n=96), review/guideline articles (n=18 and n=52), citing articles (n=3 and n=42), or contacting authors/experts (n=6 and n=37). Specific sources of unpublished studies were searched in 22 and 68 reviews, for example conference proceedings (n=4 and n=18), databases only containing conference abstracts (n=2 and n=33), or trial registries (n=12 and n=39). At least one unpublished study was included in 17 and 23 reviews. Overall, 39 of 2,082 studies (1.9%) included in non-Cochrane reviews were unpublished, and 64 of 2,780 studies (2.3%) in Cochrane reviews, most often conference abstracts (97/103).
Conclusions: Searching practices vary considerably across systematic reviews of diagnostic accuracy. Cochrane reviews seem to make more efforts to identify studies, both published and unpublished. Unpublished studies are a minimal fraction of the evidence included in recent reviews. This represents avoidable research waste, may introduce bias, and could have negative effects on patient care.
Objectives: To assess searching practices among recent systematic reviews of diagnostic accuracy, with a special focus on the identification and inclusion of unpublished studies.
Methods: We included systematic reviews if they had evaluated the diagnostic accuracy of one or more index tests against a reference standard in humans. We extracted data from 100 non-Cochrane systematic reviews of diagnostic accuracy indexed in MEDLINE and published between 10-2017 and 01-2018, and from all 100 Cochrane systematic reviews of diagnostic accuracy published by 12-2018, irrespective of whether meta-analysis had been performed.
Results: Non-Cochrane and Cochrane reviews searched a median of 4 (IQR 3-5) and 6 (IQR 5-9) databases, respectively; most often MEDLINE/PubMed (n=100 and n=100) and EMBASE (n=81 and n=100). No language restrictions were applied in 37 and 90 reviews, and efforts to contact authors in case of incomplete or unclear data were announced or reported by 31 and 78 reviews. Additional efforts to identify studies beyond searching bibliographic databases were performed in 76 and 98 reviews, most often through screening reference lists (n=71 and n=96), review/guideline articles (n=18 and n=52), citing articles (n=3 and n=42), or contacting authors/experts (n=6 and n=37). Specific sources of unpublished studies were searched in 22 and 68 reviews, for example conference proceedings (n=4 and n=18), databases only containing conference abstracts (n=2 and n=33), or trial registries (n=12 and n=39). At least one unpublished study was included in 17 and 23 reviews. Overall, 39 of 2,082 studies (1.9%) included in non-Cochrane reviews were unpublished, and 64 of 2,780 studies (2.3%) in Cochrane reviews, most often conference abstracts (97/103).
Conclusions: Searching practices vary considerably across systematic reviews of diagnostic accuracy. Cochrane reviews seem to make more efforts to identify studies, both published and unpublished. Unpublished studies are a minimal fraction of the evidence included in recent reviews. This represents avoidable research waste, may introduce bias, and could have negative effects on patient care.