Validity of subject self-report for acne.

Background/objective: Acne prevalence studies often use subject self-report as data source. Our aim was to evaluate the validity of acne self-report.

Methods: Responses of university students to an acne questionnaire were compared to the trained observer's concurrent examination of acne. The validity of self-report was measured by sensitivity, specificity, positive predictive value and negative predictive value. Agreement was measured by Cohen's kappa and correct classification percentage.

Results: The sensitivity of self-report was 0.55 (95% CI 0.47-0.63), the specificity was 0.72 (95% CI 0.63-0.80), the positive predictive value was 0.70 (95% CI 0.61-0.78), and the negative predictive value was 0.57 (95% CI 0.49-0.65). Cohen's kappa was 0.26 (95% CI 0.15-0.38) and correct classification percentage was 63.

Conclusions: Validity of self-report was moderate at best and agreement was fair, indicating that college students could not accurately report that they have acne. This is likely not sufficient for clinical or research activities or to assure that individuals who self-guide their acne therapy actually have acne.