HOW ACCURATE IS SELF-REPORTED FAMILY HISTORY OF COLORECTAL-CANCER

Much of the evidence that supports a relation between a positive famil y history of and increased risk for colorectal cancer is based on info rmation obtained exclusively from patients. There have been few assess ments of the accuracy of such data. The validity of self-reported fami ly history of colorectal cancer was assessed in the course of a case-c ontrol study of colorectal adenomas conducted among patients aged 20-7 5 years who underwent colonoscopy in Brisbane, Australia between 1980 and 1985. Family histories reported by a subsample of 237 colonoscopy patients (74 cases and 163 controls) were compared with relatives' med ical records and death certificates. Patients' reports of colorectal c ancer in 90 relatives were confirmed for 70 (77.8%; 95% confidence int erval (CI) 67.8-85.9). Among 124 reports by patients of relatives who had other abdominal cancer or bower conditions, 114 (91.9%; 95% CI 85. 7-96.1) were confirmed to be correct, while 10 (8.1%) were found to be colorectal cancer. Finally, 105 (99.1%; 95% CI 94.9-100.0) of a rando m sample of 106 completely negative reports by patients were confirmed to be correct. Overall, 77% of positive family histories (any positiv e relatives) were confirmed, and it was estimated that 98% of negative family histories (no positive relatives) were correct. Cases were sli ghtly more accurate than controls in reporting both positive and negat ive histories among their relatives. By extrapolation of these results to the total sample of 1,244 patients in the larger case-control stud y, sensitivity of self-reported positive family history was estimated to be 0.87 among cases and 0.82 among controls, and specificity was es timated to be 0.97 in both groups.