Understanding the validity of self-reported positive family history of lymphoma in extended families to facilitate genetic epidemiology and clinical practice.

The validity of self-reported information about familial Hodgkin lymphoma (HL), important for epidemiologic research and clinical practice, is undetermined. We attempted to validate 55 familial lymphomas previously reported by 48 subjects in a population-based case-control study of HL in women. Of 44 diagnoses (80%) reported by 40 (83%) recontacted subjects, we obtained medical documentation for 36 (82%). Twenty-nine (81%) were validated as lymphoma, with accuracy better for first-degree relatives and subjects with larger nuclear families and other family illness. Fourteen reports of familial HL were validated as lymphoma for 13 (93%) and as HL for nine (64%). Fifteen reports of familial NHL were validated as lymphoma for 10 (67%) and as NHL for 10 (67%). Thus, familial HL reported by HL patients and controls is highly likely to be lymphoma even in extended family members but less likely to be HL per se. Validity may vary with the subject's family size and medical history.