Comparison of telephone sampling and area sampling: Response rates and within-household coverage

Random digit dialing is used frequently in epidemiologic case-control studi es to select population-based controls, even when both cases and controls a re interviewed face-to-face. However, concerns persist about the potential biases of random digit dialing, particularly given its generally lower resp onse rates. In an Atlanta, Georgia, case-control study of breast cancer amo ng women aged 20-54 years, all of whom were interviewed face-to-face, two s tatistically independent control groups were compared: those obtained throu gh random digit dialing (n = 652) and those obtained through area probabili ty sampling (n = 640). The household screening rate was significantly highe r for the area sample, by 5.5%. interview response rates were comparable. T he telephone sample estimated a significantly larger percentage (by approxi mately 7%) of households to have no age-eligible women. Both control groups , appropriately weighted, had characteristics similar to US Census demograp hic characteristics for Atlanta women, except that respondents in both cont rol groups were more educated and more likely to be married. The authors co nclude that households contacted through random digit dialing are somewhat less likely to participate in the household screening process, and if they are cooperative, some households may not disclose that age-eligible women r eside therein. Investigators need to develop improved methods for screening and enumerating household members in random digit dialing surveys that tar get a specific subpopulation, such as women.