Are medical mailing lists reliable sources of professional advice?

Professional mailing lists are one of the more useful and popular medical resources on the Internet. Some concern has been raised about the reliability of these uncontrolled forums. We have studied some quality aspects of a subset of Internet mailing lists on nephrology. From November 1996 to March 1997 the mailing lists NEPHROL, PDIAL-L and HYPERTEL were studied. The subscribers that posted, and a representative sample of the total number of subscribers of each list, were searched in the Medline Silver-Platter database, and their individual impact factors were obtained from the Science Citation Index. In addition, the first authors of the original articles, and short communications from the more established nephrology journals, were searched similarly, in order to compare the mailing lists with the journals. NEPHROL was the most active list (7 postings/day on average). HYPERTEL had the best average impact factor among the subscribers who posted (6.6). In general, the journals showed higher average impact factors than the mailing lists, but without statistically significant differences. HYPERTEL, PDIAL-L and NEPHROL are high quality nephrology mailing lists, and can be considered as a complement to the specialized nephrology journals.