Reliability of Self-Reported Family History of Cancer in a Large Case–Control Study of Lymphoma

JNCI Journal of the National Cancer Institute, Jan 2006

Background: Case–control studies of familial cancer risk traditionally rely on self-reported family history of cancer, which may bias results due to differential recall between case patients and control subjects. To evaluate the reliability of self-reported data, we analyzed questionnaire and registry-based data on familial cancer from a population-based case–control study of malignant lymphoma. Methods: All 1508 lymphoma case patients and 1229 control subjects completed a telephone interview assessing cancer in family members. Participants were linked to the Swedish Multi-Generation Register and Cancer Register to identify confirmed cancer diagnoses in first-degree relatives. The sensitivity and specificity of self-reported familial cancer were calculated among case patients and control subjects and were compared using logistic regression. All statistical tests were two-sided. Results: Lymphoma case patients reported a family history of any cancer with statistically significantly higher sensitivity than control subjects (0.85, 95% confidence interval [CI] = 0.83 to 0.87 and 0.80, 95% CI = 0.77 to 0.82, respectively) but with marginally lower specificity (0.89, 95% CI = 0.87 to 0.91 and 0.92, 95% CI = 0.90 to 0.94, respectively). The sensitivity of self-reporting familial cancers by site ranged from less than 0.20 for rare malignancies to nearly 0.75 for more common types, whereas specificity was generally 0.98 or greater. For most sites, the reliability of self-report was similar in patients and control subjects. However, patients reported familial hematopoietic cancer with statistically significantly higher sensitivity (0.60, 95% CI = 0.57 to 0.62) than control subjects (0.38, 95% CI = 0.35 to 0.40). Odds ratios for the association between familial cancer and risk of non-Hodgkin lymphoma were consistently higher when based on self-reported, compared with registry data-based, family history of any cancer or of hematopoietic cancer. Conclusions: Reliability of self-reported family history of cancer varies between case patients and control subjects. Recall bias may thus produce biased results in case–control studies of familial cancer risk.

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Reliability of Self-Reported Family History of Cancer in a Large Case–Control Study of Lymphoma

Ellen T. Chang ) 0 1 Karin Ekstrm Smedby 0 1 Henrik Hjalgrim 0 1 Bengt Glimelius 0 1 Hans-Olov Adami 0 1 0 Affiliations of authors: Department of Medical Epidemiology and Biostatistics, Karolinska Institutet , Stockholm, Sweden (ETC, KES, H-OA); Northern Califor- nia Cancer Center , Fremont, CA (ETC); Department of Epidemiology Research, Danish Epidemiology Science Center, Statens Serum Institut , Copenhagen, Denmark (HH); Department of Oncology, Radiology and Clinical Immunol- ogy, University of Uppsala , Uppsala, Sweden ; and Department of Oncology and Pathology, Karolinska University Hospital, Karolinska Institutet , Stockholm, Sweden (BG). 2201 Walnut Ave., Suite 300, Fremont, CA 94538 ( 1 Journal of the National Cancer Institute , Vol. 98, No. 1, January 4, 2006 Background: Case-control studies of familial cancer risk traditionally rely on self-reported family history of cancer, which may bias results due to differential recall between case patients and control subjects. To evaluate the reliability of self-reported data, we analyzed questionnaire and registry-based data on familial cancer from a population-based case-control study of malignant lymphoma. Methods: All 1508 lymphoma case patients and 1229 control subjects completed a telephone interview assessing cancer in family members. Participants were linked to the Swedish MultiGeneration Register and Cancer Register to identify confirmed cancer diagnoses in first-degree relatives. The sensitivity and specificity of self-reported familial cancer were calculated among case patients and control subjects and were compared using logistic regression. All statistical tests were two-sided. Results: Lymphoma case patients reported a family history of any cancer with statistically significantly higher sensitivity than control subjects (0.85, 95% confidence interval [CI] = 0.83 to 0.87 and 0.80, 95% CI = 0.77 to 0.82, respectively) but with marginally lower specificity (0.89, 95% CI = 0.87 to 0.91 and 0.92, 95% CI = 0.90 to 0.94, respectively). The sensitivity of self-reporting familial cancers by site ranged from less than 0.20 for rare malignancies to nearly 0.75 for more common types, whereas specificity was generally 0.98 or greater. For most sites, the reliability of self-report was similar in patients and control subjects. However, patients reported familial hematopoietic cancer with statistically significantly higher sensitivity (0.60, 95% CI = 0.57 to 0.62) than control subjects (0.38, 95% CI = 0.35 to 0.40). Odds ratios for the association between familial cancer and risk of non-Hodgkin lymphoma were consistently higher when based on self-reported, compared with registry data-based, family history of any cancer or of hematopoietic cancer. Conclusions: Reliability of self-reported family history of cancer varies between case patients and control subjects. Recall bias may thus produce biased results in case-control studies of familial cancer risk. [J Natl Cancer Inst 2006;98:61-8] - Family history of hematopoietic malignancy is an established risk factor for lymphoma (114). However, in casecontrol studies in which participants are asked to report their relatives medical history, recall bias arises if awareness of family history differs systematically between case patients and control subjects. Patients with cancer may be more likely than control subjects to report a positive family history of cancer, leading to overestimated measures of association. Accuracy of reporting may also be affected by other factors, such as the age, sex, and education level of the subject and the amount of time since a family member was diagnosed with cancer. Nevertheless, family history of cancer is almost always assessed by self-report via questionnaires in observational studies because medical records of family members are difficult or impossible to obtain. In contrast to observational studies, verified cancer diagnoses in relatives can sometimes be assessed reliably in registry-based studies; however, these studies lack the detailed, individualized questionnaire data that enrich interview-based observational studies. A handful of casecontrol studies of several cancer types have described the accuracy of self-reported familial cancer (1520). However, some of these and other validation studies of familial cancer examined only positive self-reports, rather than both positive and negative reports, and the sensitivity and specificity of self-reported data cannot be calculated from such studies. Of the three casecontrol studies that assessed the accuracy of negative reports of familial cancer (16,18,20), two found substantial false-negative reporting of events (18,20). Most previous studies also suggest considerable false-positive reporting of familial cancer (1518,20), and some show differences in accuracy between individuals who had and had not been diagnosed with cancer (16,17). To our knowledge, no previous study has examined the accuracy of reporting familial cancer am (...truncated)


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Ellen T. Chang, Karin Ekström Smedby, Henrik Hjalgrim, Bengt Glimelius, Hans-Olov Adami. Reliability of Self-Reported Family History of Cancer in a Large Case–Control Study of Lymphoma, JNCI Journal of the National Cancer Institute, 2006, pp. 61-68, 98/1, DOI: 10.1093/jnci/djj005