Problems ascertaining friend controls in a case-control study of lung cancer

Willingness of newly diagnosed lung cancer patients to volunteer names of friends as potential control subjects was assessed from August through December 1988 in a case-control study at the National Cancer Institute and Naval Hospital, Bethesda, Maryland. Friend controls appeared ideal to examine a genetically determined metabolic characteristic and lung cancer risk, since potentially confounding characteristics could be matched and cooperation should be high. Only 11 of 23 cases named at least one friend. Cases interviewed during the second study month were most likely to volunteer names. Either the recency of the diagnosis of a highly fatal disease or the referral to a tertiary care research hospital may have contributed to the reluctance of cases to volunteer names. No characteristic was identified that might offer a means to increase referral of friend controls.