Mortality surveillance in collaborative trials

The Hypertension Detection and Follow-Up Program (HDFP) carried out 2 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 2 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 10 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.