Sensitivity and specificity of self-reported use of dietary supplements

Objective: To evaluate the sensitivity and specificity of a self-administered food frequency questionnaire (FFQ) - used in a cohort of 48 000 men to determine dietary supplement use. Design: Questionnaire data regarding use of dietary supplements were compared with 14 24-h recall interviews spread over a year. Setting and subjects: A random sample of 248 middle-aged and elderly Swedish men was included in the analysis. Results and conclusions: Use of any supplement in at least one interview was reported by 51% ( in three or more interviews by 38%). Sensitivity and specificity of the FFQ regarding any supplement use was 78 and 93%, respectively. Sensitivity for multivitamins, vitamins C and E was 69, 67 and 78%, respectively. The sensitivity increased to 93% and the specificity decreased to 88% when a user was defined as a person reporting use in at least three interviews. Conclusions: Dietary supplement use might be measured by a self-administered questionnaire relatively well especially when supplements are used more regularly.