Mortality surveillance in collaborative trials

The Hypertension Detection and Follow-Up Program (HDFP) carried out two pilot surveillances covering the enumerated population to test procedures to be used in assessing the ability of the program to influence life expectancy in the total population. A rigorously sequenced pilot survey of 2,611 households was conducted and carefully monitored through two mailings, telephone contacts, home visits, and communication with "contact" persons. The response rates at each stage varied among the 13 centers. Overall, there was a 42.7% yield from the first mailing; 42.5% of those receiving a second mailing was completed; 78.0% for telephone 61.3% for the home visits and 55.2% from the "contact" persons. Overall, 97.4% of all persons had vital status ascertained. The second phase relaxed the rigorous sequential survey requirements and reduced the reporting requirements from every ten days to monthly. Overall, 93.3% were successfully ascertained. Reduced survey structure, slightly increased mobility (from 12% to 13%), increased workload from 200 to 400 households per center, and a longer time interval between initial enumeration and the mortality ascertainment are among the reasons for performance decline.