[The impact factor of medical journals, a bibliometric indicator to be handled with care]

THE IMPACT FACTOR OF MEDICAL JOURNALS: Is a criterion for the assessment of their activity. Three bibliometrical indicators are published every year: the impact factor, the rapidity of citation index, which reflects the upward slope in increased citations and the duration of their actuality, reflecting the downward slope, after the peak. THE JOURNALS USED TO CALCULATE THESE INDICATORS: Are selected according to their periodicity, conformity to international editorial conventions, presence of a reading committee, of their citation frequency and, for a new journal, the earlier publications of the redaction committee and the authors. THERE ARE SEVERAL BIASES IN THE CALCULATION OF THE IMPACT FACTOR: The choice of the citations is subjective and the non-pertinence of the citations is well known. Several variables may intervene, such as the type of journal and its size, domain concerned, language of the publication, self-citations, coding of the articles depending on their nature, and the choice of the manuscripts published ("hot papers"). The impact factor is an indicator of citations and not of their quality, and can certainly not be used to assess an authors' work.