Reliability of interviewer and subject assessments of nevus counts in a study of melanoma

Several types of data are presented concerning the reliability of counting or estimating the density of nevi (moles), a major risk factor for melanoma, using methods typically employed in epidemiologic studies. First, interviewer-derived counts of nevi on the arm produced estimates of inter-observer, inter-subject, temporal and random variability, and their interactions. Second, interviewer-derived arm counts and respondent self-reports of whole body nevus density were compared. Finally, we compared male and female cases and controls with respect to their reported rates of having a relative with a malignant mole. Overall, the intra-observer reliability ranged from 55 to 81%, and was better for observers with more experience. The correlation between the interviewer counts and respondents' self-reported estimates was 0.41. The data on malignant moles in relatives suggest higher reporting rates in male cases and lower reporting in male controls relative to their female counterparts, but there is little difference by sex in the reporting of one's own nevus density.