Use of World Wide Web-based directories for tracing subjects in epidemiologic studies

The recent availability of World Wide Web-based directories has opened up a new approach for tracing subjects in epidemiologic studies. The completene ss of two World Wide Web-based directories (Canada411 and InfoSpace Canada) for subject tracing was evaluated by using a randomized crossover design f or 346 adults randomly selected from respondents in an ongoing cohort study . About half (56.4%) of the subjects were successfully located by using eit her Canada411 or InfoSpace. Of the 43.6% of the subjects who could not be l ocated using either directory, the majority (73.5%) were female. Overall, t here was no clear advantage of one directory over the other. Although Canad a411 could find significantly more subjects than InfoSpace, the number of p otential matches returned by Canada411 was also higher, which meant that a longer list of potential matches had to be examined before a true match cou ld be found. One strategy to minimize the number of potential matches per t rue match is to first search by InfoSpace with the last name and first name , then by Canada411 with the last name and first name, and finally by InfoS pace with the last name and first initial. Internet-based searches represen t a potentially useful approach to tracing subjects in epidemiologic studie s.