Background  Self-reporting is widely used in medical research. The objective of the present study was to evaluate the specificity and sensitivity of self-reported lesions of acne (scars and active lesions) obtained by an interview with the examination carried out by a dermatologist.

Methods  A questionnaire was applied to male adolescents who registered for obligatory military service. After that, skin examination was carried out.

Results  Of the 2,191 adolescents examined, 474 (21.60%) showed acne scars, and 625 (28.51%) admitted to having scars. The sensitivity of self-reported scars was 50.84%, and the specificity was 77.65%. The prevalence of active acne obtained by the dermatological examination was 85.76% and from self-reported acne was 76.12%, with a sensitivity of 80.95% and a specificity of 52.88%. Neither schooling nor social class made any difference to sensitivity or specificity.

Conclusions  Our findings showed that sensitivity and specificity of self-reported acne was very low, pointing out that, in a sample of adolescents, self-reporting of acne shows itself as an inadequate instrument for epidemiological studies.