[The impact factor: a factor of impact or the impact of a (sole) factor? The limits of a bibliometric indicator as a candidate for an instrument to evaluate scientific production].

The Impact Factor is a bibliometric quantitative parameter introduced in 1971 and used to evaluate, classify and compare scientific journals. It is essentially the ratio between the number of citations they receive, computed on the basis of those included in the Science Citation Index, and the number of published articles. It is thus a dynamic parameter and an indicator of the editorial quality of a journal. It has also been considered a putative index of the scientific production of a single author. The Impact Factor was first proposed as a useful instrument for planning library choices, programming personal journal buying and reading, and directing scientific journal editors in their editorial strategies. However, since among the numerous variables which may influence the Impact Factor there are such parameters as: the average number of bibliographical references in a single article, self-citations, "salami publications", the Impact Factor, though adequate to judge entities such as journals, institutions and whole scientific communities, seems on the contrary inadequate to evaluate accurately the quality of the single investigator, paper, and research group. Furthermore, a limited number of papers, all focused on the so-called "hot topics", may contribute to increase the Impact Factor of a single journal. There is therefore still much research to be done to find truly "objective" methods to evaluate critically the "quality" (and not only the "quantity") of the work of a single author, a scientific group, and an entire institution, so that not only quantitative, but also qualitative evidence may be acquired!