Comparison of personal interview and postal inquiry methods for assessing prevalence of angina and possible infarction

Abstract

The cardiac pain questionnaire administered by a postal inquiry was answered by 773 Norwegian men in a stratisfied sample of the interviewed on the same questions almost 3 yr previously. Median age was 57 at interview and 60 at the postal inquiry. Response rate was 86 per cent. Prevalence of angina (AP) and possible infarction (PI) was assessed from the symptom questions. The estimates of postal inquiry symptom prevalence of the interviewed population presented higher rates by the postal inquiry than from the interview: AP increased from 4.4 to 8.6, PI from 5.0 to 7.9, and AP only from 2.4 to 5.9 per 100. The conversion to symptom positives at postal inquiry was higher among interview non-specifics than other negatives. As much as 41 per cent of men with AP only status at interview converted to PI at postal inquiry. The conversion of interview symptom positives to negatives at postal inquiry was 19 per cent; lower among AP and PI than among PI only or AP only. It is concluded that though both methods seem to have a high ability to identify groups liable to excess mortality, the postal inquiry method is yielding higher prevalence rates of angina and possible infarction than the personal interview method in a Norwegian male population.