Epidemiological studies use self-reports from repeated surveys to ascertain incident disease. However, the accuracy of such measurements remains unknown, as validity studies have typically relied on data from prevalent, rather than incident, disease. This study examined the validity of self-reports in the detection of new-onset disease with measurements at baseline and follow-up conditions.
We conducted a prospective cohort study of 34,616 Finnish public-sector employees. Data from self-reported, physician-diagnosed diseases from two surveys approximately 4 years apart were compared with corresponding records in comprehensive national health registers used as the validity criterion.
There was a considerable degree of misclassification for self-reports as a measure of incident disease. The specificity of self-reports was equally high for the prevalent and incident diseases (range, 93%-99%), but the sensitivity of self-reports was considerably lower for incident than for prevalent diseases: hypertension (55% vs. 86%), diabetes (62% vs. 96%), asthma (63% vs. 91%), coronary heart disease (62% vs. 78%), and rheumatoid arthritis (63% vs. 83%).
This study suggests that the sensitivity of self-reports is substantially worse for incident than for prevalent diseases. Results from studies on self-reported incident chronic conditions should be interpreted with caution.