ATTRITION AND USE OF PROXY RESPONDENTS AND AUXILIARY INFORMATION IN THE SICILIAN NEUROEPIDEMIOLOGIC STUDY

Two-phase prevalence surveys with screening (phase 1) and examination (phase 2) are useful for some chronic diseases. Attrition, which may b ias estimates, occurs in either phase because some eligible subjects d ie before contact, some refuse to cooperate, some are incapacitated, a nd some are unreachable. This investigation relates to a survey of neu rologic diseases conducted in three municipalities of Sicily (prevalen ce date, November 1, 1987) and considers the attrition experienced and the use of proxy respondents in phase 1 and auxiliary information in phase 2 to offset, in part, this attrition. Regarding case finding, th e salvage effort was more productive for deceased and incapacitated su bjects. The age, sex, and household size of the subject were related t o phase 1 attrition, but only age was related for all four attrition g roups-deceased, refusing, incapacitated, and unreachable subjects. On the basis of information from proxy respondents, the educational level s of refusing and unreachable subjects were compared with those of sub jects screened directly. Refusing subjects were less educated, and unr eachable subjects were more educated. The proxy respondent performance , as indicated by ''don't know'' responses, was better with screening items concerning facial paralysis and mouth drooping (and not limb sen sory abnormalities or impaired consciousness), better with younger sub jects, and worse with refusing or incapacitated subjects.