INTEROBSERVER VARIABILITY AMONG PATHOLOGISTS EVALUATION OF MALIGNANT-MELANOMA - EFFECTS UPON AN ANALYTIC STUDY

This study examined whether inter-observer variability in rating tumor characteristics affected results of an investigation of surveillance bias and malignant melanoma at the Lawrence Livermore National Laborat ory. The 20 cases from the Laboratory and their 36 non-laboratory cont rols belonged to the same pre-paid health plan and were diagnosed with melanoma between 1970 and 1984. Tumors were independently and then jo intly rated by three dermatopathologists blind to the subjects' Labora tory status. The mean difference between the reviewers and the consens us reading for tumor thickness was small, ranging from -0.06 mm (95% c onfidence interval [CI] - 0.12, 0.00) to 0.00 mm (95% CI - 0.07, 0.07) . Agreement was much lower for histologic type (kappa = 0.48, 95% CI 0 .37, 0.58). Because the inter-observer variability, the study's hypoth esis was rejected by analyses based on data from the consensus reading and two reviewers, but not on data from the third reviewer. These fin dings suggest that epidemiologists using data subject to inter-observe r variability may want to employ consensus instead of individual ratin gs.