Alternative strategies for selecting population controls: comparison of random digit dialing and targeted telephone calls.
OBJECTIVE
This project was carried out to identify a valid framework for selecting controls to be used in a population-based case-control study of breast cancer, and to compare participation rates and characteristics between women contacted using a standard random digit dialing (RDD) strategy and those who were sent a letter of presentation prior to telephone contact (targeted telephone calls, TTC).


METHODS
Twelve hundred women, ages 20-74, were sampled from the Department of Motor Vehicles (DMV) and Health Care Financing Administration (HCFA) records. Women for whom telephone numbers were obtained (N = 771) were randomly assigned to RDD or TTC. The respondents participated in a brief telephone interview. Odd ratios (OR) and their 95% confidence intervals (CI) were used to estimate differences in characteristics of the respondents between the two contact strategies.


RESULTS
Telephone numbers were obtained for 79% of women aged > or = 55 years and for only 38% of women aged < 55 years. Interviews were obtained for 48% of women for whom we obtained telephone numbers, and for 77% of women for whom eligibility was confirmed via telephone contact. Participation of target women appeared to be higher for the TTC than the RDD group (42% vs. 35%, p = 0.054). Among respondents who were > or = 55 years old, those in the TTC group were 80% more likely (OR = 1.8, 95% CI: 0.9-3.4) to report a serious medical condition than women in the RDD group, 60% less likely (OR = 0.4, 95% CI: 0.2-1.0) to report having used oral contraceptives, and 80% less likely (OR = 0.2, 95% CI: 0.1-0.5) to report having had breast surgery.


CONCLUSIONS
Characteristics of respondents differed according to method of contact. These differences, along with the sampling frame used, should be considered when interpreting findings of case-control studies.
Funkhouser
E
E
Department of Epidemiology, School of Public Health, University of Alabama at Birmingham, 35294-0022, USA.
Macaluso
M
M
Wang
X
X
D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000453:epidemiology; D016022:Case-Control Studies; D015340:Epidemiologic Research Design; D005260:Female; D006801:Humans; D008875:Middle Aged; D018579:Patient Selection; D013689:Telephone