Expert review of the diagnosis and histologic classification of Hodgkin disease in a population-based cancer registry: interobserver reliability and impact on incidence and survival rates.

BACKGROUND: The reliability of Hodgkin disease (HD) diagnosis and histologic classification is an ongoing concern but has not been evaluated in a population-based case series in 20 years. Yet, diagnostic error in cancer registry data used in surveying HD occurrence may produce statistics that misrepresent incidence, mortality, or survival.
METHODS: Uniform pathology review was attempted for all 395 women ages 19--79 years with incident HD reported to a population-based cancer registry in 1988--94. Agreement between original registry and review diagnoses was measured with positive predictive values and kappa statistics. Incidence rates and survival probabilities were computed based on registry and review diagnoses.
RESULTS: Registry and review diagnosis agreed for 245 of the 362 reviewed cases. Positive predictive values varied by histologic subtype (nodular sclerosis, 95%; lymphocyte predominance, 69%; mixed cellularity, 58%; lymphocyte depletion, 0%; not otherwise specified, 40%), but agreement was good overall (kappa, 0.66, 95% confidence interval, 0.56--0.76). Eleven patients were determined not to have HD; all were older than age 44 years. Hodgkin disease incidence rates differed for original and review diagnoses only in older women, for whom registry rates slightly overestimated incidence. Five-year survival rates did not differ for registry and review data overall or by age group.
CONCLUSIONS: For most adult women patients, the diagnosis of HD was confirmed on review, reflecting the very good agreement between registry and review diagnoses for nodular sclerosis, the most common subtype. Thus, cancer registry statistics for this time period can provide accurate estimates of disease patterns for HD overall and for the nodular sclerosis variant. For other histologic subtypes, rates may be unreliable, and HD occurrence overall may be less dependable in populations with larger proportions of these subtypes. Copyright 2001 American Cancer Society.