Validity of self-reported diabetes varies with sociodemographic charecteristics: Example from Iran

Introduction: The purpose of this study was to examine the validity of self-report diabetes according to socio-demographic characteristics in participants of Ravansar Non-Communicable Diseases (RaNCD) cohort study. Methods: The study population included 10182 adults (35-65 years old) participating in RaNCD. The 'gold standard' for diagnosis of diabetes mellitus was taken as a history of relevant medicine use and/or measurement of fasting blood glucose indicating diabetes. Self-report data collected before the clinical examinations through interviews by well-trained staff. Sensitivity, specificity, and positive and negative predictive values were used to estimate the accuracy of self-report in diabetes. Results: Of the 10182 individuals invited to participate in the RaNCD, 96 people were not willing to participate in the study (participation rate = 99.06%). The prevalence of diabetes by self-report and gold standard was 10.04% and 8.19% respectively. Among those who said they had diabetes, 389 (38.78%) did not have diabetes. Self-reported diabetes had sensitivity, specificity, positive and negative predictive values of 75.0%, 95.8%, 61.2% and 97.7%, respectively. Being female, aging, smoking, and having a family history of diabetes increased the chance of false positive; and being male, having a family history of diabetes, aging, and increasing BMI increased the chance of false negative. Conclusions: Although the overall validity of self-report in diabetes seems to be acceptable in the study population with a correction factor of 25.3%, it should be noted that the is influenced by age, gender, and family history of diabetes.