[The impact factor--a reliable sciento-metric parameter?].

With shortage of research funds and increasing competition for medical posts, performance indicators and control instruments are being looked for in order to be able to allot research funds and make professorial appointments in relation to scientific performance. Incomprehensibly for many, the impact factor has become the decisive scientometric indicator at German universities despite of substantial systematic limitations. The impact factor is derived from the journal citation reports. Its basis of calculation entails the following problems: the editorial board of the private Institute of Scientific Information (ISI) decides on whether a journal is to be classified as a source journal. The citation index of all journals is calculated from their citations alone. Crucial means of influencing the impact factor result from self-citations and citation groups in these source journals. Languages other than English and other than Latin alphabets are appreciably disadvantaged by the citation index, which is why for example despite its international significance the rapid development of the osteosynthesis technique in German speaking countries went unnoticed by British and American orthopedic surgeons and scientists. The articles on postgraduate training necessarily published by clinicians in the respective language of their country are not cited because the addresses of such publications do not engage in research. Clinical disciplines (especially highly specialized disciplines such as trauma and hand surgery) thus attain appreciably lower impact factors for their journals than basic disciplines and interdisciplinary clinical sectors which lead the ranking of journals. The period covered in calculating the impact factor is only 2 years. Very modern and widely disseminated organs of publication with a short information halflife are favored. From the 10 objectively most often cited and most important journals for the scientific society, only 2 are to be found amongst those with the highest impact factor. The impact front-runner from 1995 has a very low absolute number of citations. The impact factor provides limited statistical information on a journal in its special field. Using it for this purpose presupposes knowledge of rules, limitations and constraints. Its uncritical use as a general currency of science is fundamentally unscientific. In addition, this leads to the specialists in the field knowledge of the universities being disregarded in favor of a pseudo-objective parameter determined elsewhere. At all events, correction factors for the impact factor have to be applied in respect to the different disciplines. The faculties should reach agreement on relevant (also on German language) organs of publication. The impact factor is not suitable as an indicator of the research activity and the quality of a researcher or an institution. Besides careful human judgement and other classical methods of decision making, the Science Citation Index can contribute to the individual evaluation.