Accuracy of Offspring Reports of Parental Cardiovascular Disease History: The Framingham Offspring Study

Context Although physicians use the family history in their assessment of cardiovascular disease risk, the accuracy of patient reports of family history is unknown. Contribution Using Framingham Heart Study data spanning 2 generations, the authors compared participant reports of parental history with parents' health records. Specificity was high and sensitivity was low for all items. Conclusion A positive family history item is probably accurate. A negative family history item is often inaccurate. The Editors A report of a positive family history confers an increased risk for cardiovascular disease and risk factors in first-degree relatives (1-10). Therefore, physicians use self-reported information about family history to infer the risk for cardiovascular disease in their patients, develop screening strategies, and target primary prevention efforts (11). Although most of the information about family history that is available to physicians is limited to individual patient reports of their family members' disease status, little is known about the accuracy of these reports. Previous work has largely evaluated a person's reported family history compared with the relatives' self-reported medical history (12). Few studies have validated the reported family history information with medical record information (13-15) or direct clinical assessment of the affected relatives (16). These studies have been limited to reports provided by high school students (15, 16), accounts of deceased relatives using data from death certificates (14), or small casecontrol studies restricted to male reporters (15). A better understanding of the magnitude of misreporting of family history information and the factors related to misreporting is needed to enhance physicians' ability to reliably use a patient's reported family history and identify those at increased risk for disease. This will allow prevention efforts to be focused most effectively. The multigenerational design of the Framingham Heart Study provides the unique opportunity to examine the accuracy of reported parental history information because of the availability of validated events and objective clinical assessments in a 2-generation population-based sample. We also sought to evaluate the effects of age, sex, and birth order on offspring reports of parental history. In addition, we assessed whether a less restrictive definition of cardiovascular disease might improve reporting. Methods Study Sample The Framingham Heart Study was established in 1948 when 5209 residents of Framingham, Massachusetts, 28 to 62 years of age, were enrolled in a prospective epidemiologic cohort study. Members of the original cohort have undergone follow-up examinations every 2 years. In 1971, 5124 offspring of the original cohort members and offspring spouses were enrolled in the Framingham Offspring Study. These participants undergo follow-up examinations approximately every 4 years. Study design and entry criteria have been reported elsewhere (17, 18). The Institutional Review Board at Boston Medical Center approved the examination content for both offspring and original cohort examinations. Family History Questionnaire From 1995 to 1998, offspring participants who attended a routine research examination (1656 men and 1875 women) were asked to complete a self-administered Awareness of Coronary Factors questionnaire that included questions about cardiovascular risk factors and disease for themselves and their parents. Participants were asked, Did your parents and did you ever have high blood pressure, ever have high blood cholesterol >6.2 mmol/L (>240 mg/dL), ever have diabetes mellitus, have a heart attack before age 55, have a stroke before age 65, or die of heart disease? Participants reported separately for their father and mother. Final Study Sample Only offspring participants who had both natural parents in the original cohort of the Framingham Heart Study were eligible for inclusion in this study. Exclusions included 682 offspring with only one parent in the original cohort, 15 offspring with neither parent in the original cohort, and 1079 offspring spouses. An additional 10 offspring participants were excluded because parental data were unavailable. Reports of parental history information were missing for 117 participants who were excluded. Therefore, the study sample consisted of 791 male offspring reporters and 837 female offspring reporters. Ascertainment of Risk Factors Research examinations included 2 measurements of resting blood pressure obtained by physicians, a physician-administered medical history questionnaire and physical examination for the presence of symptoms and signs of cardiovascular disease, resting electrocardiography, and blood specimens for glucose and cholesterol levels. Parental hypertension was defined as a blood pressure of 160/95 mm Hg or greater or the use of antihypertensive medications on at least 2 research examinations. We did not use criteria for hypertension recommended in the sixth report of the Joint National Committee on Prevention, Detection, and Treatment of High Blood Pressure because many original cohort members died before publication of these criteria (19). Diabetes mellitus was defined as a random blood glucose level of 11.1 mmol/L (200 mg/dL) or greater or the use of insulin or oral hypoglycemic agents. High blood cholesterol level was considered present if the total cholesterol level was 6.2 mmol/L (240 mg/dL) or greater or if the parent was using cholesterol-lowering medications on at least 2 research examinations. Risk factors in offspring reporters were defined by using more contemporary criteria and were considered to be present if criteria were met at 2 or more research examinations attended or at the examination at which the parental history data were collected. Offspring hypertension was defined as a blood pressure reading of 140/90 mm Hg or greater or use of blood pressurelowering medication. Diabetes was defined as a fasting blood glucose level of 7.77 mmol/L (140 mg/dL) or greater or use of insulin or oral hypoglycemic agents. Current recommendations to diagnose diabetes by using a fasting glucose of 6.99 mmol/L (126 mg/dL) or greater were not in effect at the time of this study (20). High blood cholesterol level was considered present for a total cholesterol level of 6.2 mmol/L (240 mg/dL) or greater or use of cholesterol-lowering medication. Validation of Cardiovascular Outcomes An end point committee panel of 3 senior physician investigators reviewed all available information (Framingham Heart Study research examination records, outside personal physician and hospital records, and next-of-kin interviews) to determine the presence of myocardial infarction and to assign a cause of death. A panel of study neurologists reviewed all available information for suspected cases of stroke and transient ischemic attack. Uniform criteria for all cardiovascular disease end points and causes of death have been in place for both the original cohort and offspring since study inception. Statistical Analysis Offspring parental history reports were compared with parental data recorded in the research database. Sensitivity, specificity, positive and negative predictive values (and their 95% CIs) of offspring reports for parental risk factors, and cardiovascular events were calculated. Sensitivity measures the proportion of the offspring sample with a parent with the condition that has a positive offspring report, and specificity measures the proportion of the offspring sample with a parent free of the condition that has a negative offspring report. Positive predictive value estimates the probability that the parent has the condition, given a positive offspring report, whereas negative predictive value measures the probability that the parent does not have the condition, given a negative offspring report. Because predictive values depend on the prevalence of disease or no disease in the study sample, likelihood ratios were calculated as follows: The positive likelihood ratio was the ratio of sensitivity to 1 minus specificity and the negative likelihood ratio was the ratio of 1 minus sensitivity to specificity. The likelihood ratio, positive or negative, measured the change in odds of disease in the parent, given a positive or negative offspring report (21). Any participant response of unsure or unknown or a failure to provide a response for a given condition in the parent led to a classification of no (the parent did not have the condition). The study sample included 469 families with 2 or more offspring reporters. In these families, we examined whether differences exist in the correctness of parental history reports between the oldest and youngest sibling. To examine whether a less restrictive definition of heart attack affected the parental history report, we identified the fathers of all offspring participants with a false-positive report of a heart attack before age 55 years (report was not confirmed using our end point committee criterion for myocardial infarction). The research medical record of each father was reviewed to determine whether a heart attack occurred at age 55 years or older or if other types of coronary heart disease events had occurred. We then examined positive predictive values for each of 3 broadened definitions of heart attack: heart attack at any age, coronary heart disease before age 55, and coronary heart disease at any age. Likewise, we examined the change in positive predictive value for stroke when the definition of stroke was broadened from stroke before the age of 65 years to stroke at any age, and the change in positive predictive value for die of heart disease when the definition was broadened to death from cardiovascular disease (excluding stroke death). All statistical analyses were performed by using SAS statistical software, version 8 (SAS Institute, Inc., Cary, North Carolina) (22). Results Our study sample