Review of the usefulness of contacting other experts when conducting a literature search for systematic reviews. The comprehensiveness of Medline and Embase computer searches. Searches for controlled trials of homoeopathy, ascorbic acid for common cold and ginkgo biloba for cerebral insufficiency and intermittent claudication. Beyond Medline: reducing bias through extended systematic review search. Lessons for search strategies from a systematic review, in The Cochrane Library, of nutritional supplementation trials in patients after hip fracture. Developing methods for systematic reviewing in health services delivery and organization: an example from a review of access to health care for people with learning disabilities. Part 1. Identifying the literature. Systematic reviews of health effects of social interventions: 1. Finding the evidence: how far should you go? Searching one or two databases was insufficient for meta-analysis of observational studies. Spinal palpation: The challenges of information retrieval using available databases. Searching multiple databases for systematic reviews: added value or diminishing returns? Effectiveness and efficiency of search methods in systematic reviews of complex evidence: audit of primary sources.
nan To assess the comprehensiveness of Medline and Embase computer searches for controlled trials.
                Comparison of articles found after an exhaustive search of the literature with the yield of a Medline or Embase search. This was performed for controlled clinical trials on the efficacy of three interventions: homoeopathy, ascorbic acid for common cold, and ginkgo biloba for intermittent claudication and cerebral insufficiency. The number of controlled trials found by exhaustive search of the literature was 107, 61 and 45, respectively.
                For homoeopathy, ascorbic acid and ginkgo the proportion of all trials found by Medline was 17%, 36% and 31% respectively and for Embase 13%, 25% and 58% respectively. After checking of the references in the Medline articles 44%, 79% and 76% of all trials were identified. After checking of the references in the Embase articles 42%, 72% and 93% of all trials were identified. About 20% of the articles was not correctly indexed. Of the best trials 68%, 91% and 83% could be found with Medline and 55%, 82% and 92% of the best trials were identified through Embase.
                For the topics mentioned, Medline and Embase searches are sufficient to get an impression of the evidence from controlled trials, but only if references in the articles are followed for further evidence. If one wants to get a more complete picture, additional search strategies make sense. Of course, this picture may be different for other topics. To evaluate the sensitivity and precision of various extended search methods in identifying randomized controlled trials (RCTs) for systematic reviews.
                Prospective analysis of extended search methods (specialized databases or trial registries, reference lists, hand-searching, personal communication, and Internet) used in two systematic reviews of RCTs. The gold standard was the total number of RCTs identified by major databases (MEDLINE, EMBASE, etc.) and extended search strategies combined. Sensitivity was the proportion of all known RCTs identified by any extended search method. Precision reflected the proportion of all items uncovered by any extended search method that actually were RCTs.
                The extended search identified 94 additional RCTs for the systematic reviews beyond those identified with the major databases. Specialized databases and trial registries had the highest sensitivity and precision for the lipid-lowering project (13.6% and 52.7%, respectively; p < .05) followed by scanning of reference lists (7.2% sensitivity and 41.9% precision; p <.05). Hand-searching was more effective than personal communication and Internet searching (1.7% sensitivity and 12.2% precision; p < .05). The acupuncture project had slightly different results, with the specialized databases and trial registries tied with the review of reference lists for highest sensitivity (14.2%). The precision followed the same trend as the lipid-lowering project (17.6% specialized databases; 8.3% reference lists; p < .05). A post-hoc analysis showed that 75 of the 94 RCTs were indexed in the major databases but missed by the major database search.
                Extended searching identified additional RCTs for the systematic reviews beyond those found in major databases. Specialized databases and trial registries were most effective. An important number of RCTs were missed by the major database search. Timing and accuracy of indexing may explain this finding. The definitive measure, whether there is an association between the method used to uncover RCTs, the quality of the items uncovered and their impact on systematic review results, is yet to be determined. A key aim when conducting systematic reviews of randomized controlled trials (RCTs) is to include all of the evidence, if possible. Serious bias may result if trials are missed through inadequate search strategies.
                The objective was to evaluate the search plan for identifying RCTs in nutrition as part of a systematic review, in The Cochrane Library, of nutritional supplementation trials in patients after hip fracture.
                We identified potential studies by searching the electronic databases BIOSIS, CABNAR, CINAHL, EMBASE, HEALTHSTAR, and MEDLINE; reference lists in trial reports; and other relevant articles. We also contacted investigators and other experts for information and searched 4 nutrition journals by hand.
                We identified 15 RCTs that met the predefined inclusion criteria. The search plan identified 8 trials each in EMBASE, HEALTHSTAR, and MEDLINE and 7 in BIOSIS and CABNAR. BIOSIS was the only electronic database source of 2 trials. Eleven trials were identified by searching electronic databases and 2 unpublished trials were identified via experts in the field. We found one trial, published only as a conference abstract, by searching nutrition journals by hand. After publication of the protocol for the review in The Cochrane Library, we were informed of another unpublished trial.
                We found that a limited search plan based on only MEDLINE or one of the other commonly available databases would have failed to locate nearly one-half of the studies. To protect against bias, the search plan for a systematic review of nutritional interventions should be comprehensive. Our objectives were to identify literature on: (i) theory, evidence and gaps in knowledge relating to the help-seeking behaviour of people with learning disabilities and their carers; (ii) barriers experienced by people with learning disabilities in securing access to the full range of health services; (iii) interventions which improve access to health services by people with learning disabilities.
                twenty-eight bibliographic databases, research registers, organizational websites or library catalogues; reference lists from identified studies; contact with experts; current awareness and contents alerting services in the area of learning disabilities.
                Inclusion criteria were English language literature from 1980 onwards, relating to people with learning disabilities of any age and all study designs. The main criteria for assessment was relevance to the Guilliford et al. model of access to health care (Gulliford et al. Access to health care. Report of a Scoping Exercise for the National Co-ordinating Centre for NHS Service Delivery and Organisation R & D (NCCSDO). London: NCCSDO, 2001), which was modified to the special needs of people with learning disabilities. Inclusion criteria focused on relevance to the model with initial criteria revised in light of literature identified and comments from a consultation exercise with people with learning disabilities, family and paid carers and experts in the field. Data abstraction was completed independently and selected studies were evaluated for scientific rigour and the results synthesized.
                In total, 2221 items were identified as potentially relevant and 82 studies fully evaluated.
                The process of identifying relevant literature was characterized by a process of clarifying the concept under investigation and sensitive search techniques which led to an initial over-identification of non-relevant records from database searches. Thesaurus terms were of limited value, forcing a reliance on using free-text terms and alternative methods of identifying literature to supplement and improve the recall of the database searches. A key enabler in identifying relevant literature was the depth and breadth of knowledge built up by the reviewers whilst engaged in this process. There is little guidance on how to identify useful evidence about the health effects of social interventions. The aim of this study was to assess the value of different ways of finding this type of information.
                Retrospective analysis of the sources of studies for one systematic review.
                Case study of a systematic review of the effectiveness of interventions in promoting a population shift from using cars towards walking and cycling.
                Only four of the 69 relevant studies were found in a "first-line" health database such as Medline. About half of all relevant studies were found through the specialist Transport database. Nine relevant studies were found through purposive internet searches and seven relevant studies were found by chance. The unique contribution of experts was not to identify additional studies, but to provide more information about those already found in the literature.
                Most of the evidence needed for this review was not found in studies indexed in familiar literature databases. Applying a sensitive search strategy across multiple databases and interfaces is very labour intensive. Retrospective analysis suggests that a more efficient method might have been to search a few key resources, then to ask authors and experts directly for the most robust reports of studies identified. However, internet publications and serendipitous discoveries did make a significant contribution to the total set of relevant evidence. Undertaking a comprehensive search may provide unique evidence and insights that would not be obtained using a more focused search. To address methodologic issues in searching for observational studies by presenting database search methods and results.
                Results of two literature searches for publications reporting on observational studies of alcohol consumption and the risk of breast cancer and large bowel cancer were compared, to evaluate the sensitivity of various bibliographic databases and search strategies, including hand-searching reviews and meta-analyses.
                The target sensitivity of 90% of publications in the breast cancer search was achieved by starting with Medline, then adding Biosis, Embase, and SCI EXPANDED-SSCI, which provided a total of 72 (91%) of the 79 relevant publications. To reach a similar 89% sensitivity for large bowel cancer, at least Biosis, Dissertation Abstracts Online, Embase, ETOH, and Medline had to be searched, with the addition of hand search of reviews and meta-analyses.
                Limiting a search to one or two databases when conducting meta-analyses of observational studies will not provide a thorough summary of the existing literature. The findings support recommendations to implement a comprehensive search of electronic databases and the reference lists of recent review articles and meta-analyses. This study addressed 2 questions: first, what is the yield of PubMed MEDLINE for complementary and alternative medicine (CAM) studies compared to other databases; second, what is an effective search strategy to answer a sample research question on spinal palpation?
                We formulated the following research question: "What is the reliability of spinal palpation procedures?" We identified specific Medical Subject Headings (MeSH) and key terms as used in osteopathic medicine, allopathic medicine, chiropractic, and physical therapy. Using PubMed, we formulated an initial search template and applied it to 12 additional selected databases. Subsequently, we applied the inclusion criteria and evaluated the yield in terms of precision and sensitivity in identifying relevant studies.
                The online search result of the 13 databases identified 1189 citations potentially addressing the research question. After excluding overlapping and nonpertinent citations and those not meeting the inclusion criteria, 49 citations remained. PubMed yielded 19, while MANTIS (Manual Alternative and Natural Therapy Index System), a manual therapy database, yielded 35 citations. Twenty-six of the 49 online citations were repeatedly indexed in 3 or more databases. Content experts and selective manual searches identified 11 additional studies. In all, we identified 60 studies that addressed the research question. The cost of the databases used for conducting this search ranged from free-of-charge to $43,000 per year for a single network subscription.
                Commonly used databases often do not provide accurate indexing or coverage of CAM publications. Subject-specific specialized databases are recommended. Access, cost, and ease of using specialized databases are limiting factors. To explore whether searching specialised bibliographic databases identified additional relevant papers to those located by a Medline search for a systematic review of exercise therapy.
                Searches were performed in Medline, two further generalised medical databases (Embase, Cochrane Library) and four specialised databases (CancerLit, Cinahl, PsychInfo, SportDiscus) to identify controlled trials of exercise interventions for cancer patients.
                A total of 749 different publications were located through the search, of which 18 met inclusion criteria. Fifteen (83%) of these were identified through Medline and three (17%) from three individual specialised databases. A further seven studies meeting inclusion criteria were located through reference lists and contact with experts.
                In this example, searching Medline and additional specialised databases along with checking reference lists and contacting experts was the most effective means of ensuring that all relevant papers were included in the review. Searching Medline alone for systematic reviews of exercise or other unconventional therapies is likely to be inadequate. To describe where papers come from in a systematic review of complex evidence. Method Audit of how the 495 primary sources for the review were originally identified.
                Only 30% of sources were obtained from the protocol defined at the outset of the study (that is, from the database and hand searches). Fifty one per cent were identified by "snowballing" (such as pursuing references of references), and 24% by personal knowledge or personal contacts.
                Systematic reviews of complex evidence cannot rely solely on protocol-driven search strategies.
There is some evidence to support the use of checking reference lists for locating studies in systematic reviews. However, this evidence is derived from weak study designs. In situations where the identification of all relevant studies through handsearching and database searching is difficult, it would seem prudent that authors of reviews check reference lists to supplement their searching. The challenge, therefore, is for review authors to recognize those situations.