Impact factor: A valid measure of journal quality?

Objectives: 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.