Journal impact factor and individual article impact

In the October issue of the American Journal of Emergency Medicine, Dr Li et al [ ] tried to quantify national contributions to emergency medicine (EM) research by analyzing the publications in highly cited EM journals. There were 2 points in this article that may be misleading. First, EM journals were classified into category of “emergency medicine” not category of “critical care medicine” in 2010 Journal Citation Reports (JCR) [ ]. The EM journals were classified into different categories before 1990 JCR. In 1991 JCR, EM journals were classified into category of “critical care,” and this category was renamed “emergency medicine and critical care” in 1996 JCR. This category was divided into “critical care medicine” and “emergency medicine” in 2000 JCR. The number of journals in category of emergency medicine increase from12 in 2000 JCR to 23 in 2010 JCR [ ]. Second, the journal impact factor is not representative of individual article citations and quality because of the skewed distributions of articles' citation [ , , ]. Therefore, adopting the accumulated impact factors and the average impact factor of each country as a measurement of contribution may not be feasible. It is the article citations that determine the journal impact factor, not vice versa. Based on the same phenomena that the citations of articles are skewed distribution, highly plus rarely cited articles and evenly cited articles all lead to the same mean citation. The mean citation alone without other descriptive statistic parameters (eg, median, mode, SD, skewness, and kurtosis) only disclosed part of the whole picture of national contributions to EM research.