Questionnaire items to assess skin color and erythemal sensitivity: reliability, validity, and "the dark shift".

BACKGROUND: Skin pigmentation is a key factor for UV radiation exposure related cancers. To appropriately target cancer control activities related to this exposure and for better representation in epidemiologic studies, a valid and reliable assessment of skin color is required.
METHODS: The validity and reliability of two self-report measures were assessed: skin color and erythemal sensitivity. A sample of 289 university students categorized their unexposed skin color and photosensitivity via a questionnaire. Skin color was also measured by spectrophotometer. After 7 days, participants repeated the self-report assessment.
RESULTS: Significant correlations were found for both self-report items with objective measures, indicating that these items may be valid assessment tools (color: Spearman's rho=-0.75, P<0.001; photosensitivity: Spearman's rho=-0.64, P<0.001). No sex differences in validity were evident. Stronger correlations were found among those of European than those of non-European ethnicity (color: Spearman's rho=-0.78 versus -0.59, bootstrap P=0.007; photosensitivity: Spearman's rho=-0.63 versus -0.28, bootstrap P=0.001). Strong biases toward overestimation of skin pigmentation were evident, ranging from 36% in the self-identified fair skin group to 77% in the medium skin color group. Intrarater reliability of the questionnaire items was high (color: k=0.78, P<0.001; photosensitivity: k=0.77, P<0.001).
CONCLUSIONS: Study findings suggest that self-report may be a valid measurement strategy when assessing skin type, but there is a bias toward overestimation of skin color and, potentially, UV radiation resilience. IMPACT: This bias has the potential to undermine the effectiveness of skin cancer prevention efforts and needs to be addressed in health promotion programs. Copyright (c) 2010 AACR