title: Impact factor: a valid measure of journal quality?
abstract: OBJECTIVE
  Impact factor, an index based on the frequency with which a journal's articles are cited in scientific publications, is a putative marker of journal quality. However, empiric studies on impact factor's validity as an indicator of quality are lacking. The authors assessed the validity of impact factor as a measure of quality for general medical journals by testing its association with journal quality as rated by clinical practitioners and researchers.
  
  
  METHODS
  We surveyed physicians specializing in internal medicine in the United States, randomly sampled from the American Medical Association's Physician Masterfile (practitioner group, n = 113) and from a list of graduates from a national postdoctoral training program in clinical and health services research (research group, n = 151). Respondents rated the quality of nine general medical journals, and we assessed the correlation between these ratings and the journals' impact factors.
  
  
  RESULTS
  The correlation between impact factor and physicians' ratings of journal quality was strong (r2 = 0.82, P = 0.001). The correlation was higher for the research group (r2 = 0.83, P = 0.001) than for the practitioner group (r2 = 0.62, P = 0.01).
  
  
  CONCLUSIONS
  Impact factor may be a reasonable indicator of quality for general medical journals.
authors.affiliation: Division of Medical Informatics & Outcomes Research, Portland VA Medical Center and Oregon Health & Science University, Portland VA Medical Center (P3MED) 3710 Southwest US. Veterans Hospital Road Portland, Oregon 97207, USA. sahas@ohsu.edu
authors.forename: Somnath
authors.initials: S
authors.lastname: Saha
authors.forename: Sanjay
authors.initials: S
authors.lastname: Saint
authors.forename: Dimitri A
authors.initials: DA
authors.lastname: Christakis
mesh_terms: D000328:Adult; D015706:Bibliometrics; D005260:Female; D006801:Humans; D007388:Internal Medicine / Q000706:statistics & numerical data; D016243:Library Collection Development / Q000592:standards; D008297:Male; D008875:Middle Aged; D010506:Periodicals as Topic / Q000145:classification / Q000592:standards* / Q000706:statistics & numerical data*; D010820:Physicians / Q000706:statistics & numerical data; D011897:Random Allocation; D015203:Reproducibility of Results; D012108:Research Personnel / Q000706:statistics & numerical data; D012737:Sex Factors; D012922:Social Change; D011795:Surveys and Questionnaires; D014481:United States / Q000453:epidemiology