Factors associated with response to a follow-up postal questionnaire in a cohort of American Indians.

OBJECTIVE: The aim of the study was to collect pilot data on response rates to a follow-up postal questionnaire in a cohort of American Indians living in the Southwestern United States. We tested the effect of questionnaire length on response. METHODS: Cohort members were American Indian adults aged 18 and over who completed the baseline study visit. Study participants (N=1587), cohort members who completed the baseline study visit during the first year of enrollment, were randomized into two groups to receive either an 18-page or 3-page follow-up postal questionnaire. Data were collected between October 2005 and March 2006. RESULTS: The response rates after two questionnaire mailings and a reminder postcard were significantly higher for the short versus the long (56.2%, 48.1% p= < 0.01) questionnaire. Being female and being aged 50 or older were associated with returning a completed questionnaire. A reminder postcard and second mailing improved response by 11.7% and 13.4% respectively. CONCLUSIONS: These results show that a postal questionnaire can be used in a cohort of American Indians living in the Southwest, but suggest that questionnaires should be short and repeat mailings are needed.

Recruiting Hispanic women for a population-based study: validity of surname search and characteristics of nonparticipants.

Conducting research on the health of Hispanic populations in the United States entails challenges of identifying individuals who are Hispanic and obtaining good study participation. In this report, identification of Hispanics using a surname search and ethnicity information collected by cancer registries was validated, compared with self-report, for breast cancer cases and controls in Utah and New Mexico. Factors influencing participation by Hispanics in a study interview in 2000-2005 were evaluated. The positive predictive value of identification as Hispanic by cancer registry records and surname search was 82.3% for cases and 73.2% for controls. Hispanics who were correctly classified differed from those who were misclassified, reporting lower language acculturation and educational attainment. Older age was positively associated with success in contacting Hispanic controls (p(trend) < 0.0001) but negatively associated with cooperation with the interview (p(trend) < 0.0001). Community characteristics described by US Census data, including income, education, and urban/rural residence, did not significantly influence participation by Hispanic cases or controls. The authors conclude that a surname search efficiently identifies Hispanics, although individuals identified using this method are not completely representative. Recruitment of Hispanic cases and controls does not appear to be affected by selection bias related to community characteristics.