BMC Medicine BioMed Central

BackgroundSystematic reviews summarize all pertinent evidence on a defined health question. They help clinical scientists to direct their research and clinicians to keep updated. Our objective was to determine the extent to which systematic reviews are clustered in a large collection of clinical journals and whether review type (narrative or systematic) affects citation counts.MethodsWe used hand searches of 170 clinical journals in the fields of general internal medicine, primary medical care, nursing, and mental health to identify review articles (year 2000). We defined 'review' as any full text article that was bannered as a review, overview, or meta-analysis in the title or in a section heading, or that indicated in the text that the intention of the authors was to review or summarize the literature on a particular topic. We obtained citation counts for review articles in the five journals that published the most systematic reviews.Results11% of the journals concentrated 80% of all systematic reviews. Impact factors were weakly correlated with the publication of systematic reviews (R2 = 0.075, P = 0.0035). There were more citations for systematic reviews (median 26.5, IQR 12 – 56.5) than for narrative reviews (8, 20, P <.0001 for the difference). Systematic reviews had twice as many citations as narrative reviews published in the same journal (95% confidence interval 1.5 – 2.7).ConclusionsA few clinical journals published most systematic reviews. Authors cited systematic reviews more often than narrative reviews, an indirect endorsement of the 'hierarchy of evidence'.

[1]  K. Shojania,et al.  Taking advantage of the explosion of systematic reviews: an efficient MEDLINE search strategy. , 2001, Effective clinical practice : ECP.

[2]  I. Chalmers.  The Cochrane Collaboration: Preparing, Maintaining, and Disseminating Systematic Reviews of the Effects of Health Care , 1993, Annals of the New York Academy of Sciences.

[3]  K. Dickersin,et al.  Identification of meta-analyses. The need for standard terminology. , 1990, Controlled clinical trials.

[4]  G H Guyatt,et al.  Publication bias: a brief review for clinicians. , 2000, Mayo Clinic proceedings.

[5]  Gordon H. Guyatt,et al.  Users' Guides to the Medical Literature: A Manual for Evidence-Based Clinical Practice; Users' Guides to the Medical Literature: Essentials of Evidence-Based Clinical Practice , 2003, BMJ : British Medical Journal.

[6]  Kirby P. Lee,et al.  Association of journal quality indicators with methodological quality of clinical research articles. , 2002, JAMA.

[7]  F. Mosteller,et al.  A comparison of results of meta-analyses of randomized control trials and recommendations of clinical experts. Treatments for myocardial infarction. , 1992, JAMA.

[8]  R. Brian Haynes,et al.  Developing optimal search strategies for detecting clinically sound studies in MEDLINE. , 1994, Journal of the American Medical Informatics Association : JAMIA.

[9]  K A McKibbon,et al.  Locating and Appraising Systematic Reviews , 1997, Annals of Internal Medicine.

[10]  C. Mulrow.  The medical review article: state of the science. , 1987, Annals of internal medicine.

[11]  P. Seglen,et al.  Education and debate , 1999, The Ethics of Public Health.

[12]  R. Brian Haynes,et al.  Enhancing Retrieval of Best Evidence for Health Care from Bibliographic Databases: Calibration of the Hand Search of the Literature , 2001, MedInfo.

[13]  Carol Lefebvre,et al.  The effect of postings information on searching behaviour A statistical approach to designing search filters to find systematic reviews : objectivity enhances accuracy , 2001 .

[14]  David Moher,et al.  The Medical Review Article Revisited: Has the Science Improved? , 1999, Annals of Internal Medicine.