Electronic telephone directory listings: Preferred sampling frame for a population-based study of childhood cancer in Australia

PURPOSE: We report our telephone-based system for selecting community contr ol series appropriate for a complete Australia-wide series of Ewing's sarco ma cases. METHODS: We used electronic directory random sampling to select age-matched controls. The sampling has all listed telephone numbers on an up dated CD Rom. RESULTS: 95% of 2245 telephone numbers selected were successfully contacted . The mean number of attempts needed was 1.94, 58% answering at the first a ttempt. On average, we needed 4.5 contacts per control selected. Calls were more likely to be successful (reach a respondent) when made in the evening (except Saturdays). The overall response rate among contacted telephone nu mbers was 92.8%. Participation rates among female and male respondents were practically the same. The exclusion of unlisted numbers (13.5% of connecte d households) and unconnected households (3.7%) led to potential selection bias. However, restricting the case series to listed cases only, plus havin g external information on the direction of potential bias allow meaningful interpretation of our data. CONCLUSION: Sampling from an electronic directory is convenient, economical and simple, and gives a very good yield of eligible subjects compared to o ther methods. (C) 2000 Elsevier Science Inc. All rights reserved.