Variations in the agreement of self-reported cancer: A Danish nationwide study.

Previous studies show that the agreement between self-reported and registry-documented diseases varies across diseases. Few studies have addressed these challenges across site-specific cancer diagnoses. The present study aimed to examine the sensitivity and negative predictive value (NPV) of self-reported cancer in a Danish nationwide survey among adults aged ≥16 years, using registry data as the criterion standard. Moreover, the influence of sociodemographic variables and time since diagnosis on sensitivity was explored using multiple logistic regression models. Self-reported data on cancer history of any site were derived from the Danish National Health Survey 2017 (n = 183 372). Individual-level survey data were linked to data from the Danish Cancer Registry on 10 site-specific cancer diagnoses. NPV was consistently high ≥99.5% across the included cancer diagnoses. In contrast, sensitivity varied greatly and was lowest for cancer in brain/central nervous system (CNS) among both men (25.6%) and women (23.9%) and highest for rectal cancer among men (96.9%) and for breast cancer among women (98.9%). Sensitivity was also relatively low for nonmelanoma skin cancer (41.4% among men; 44.6% among women) and urinary tract cancer (60.0% among men; 60.4% among women). When restricting diagnostic definitions for cancer in brain/CNS and urinary tract cancer to include only malignant neoplasms, sensitivity increased. For several cancer diagnoses, sensitivity decreased with increasing age and lower educational level, whereas conflicting results were observed for time from diagnosis to self-report. Future studies are encouraged to use self-reported cancer history data with caution and for example, include questions on only site-specific cancer diagnoses with high sensitivity.