Research ArticlesValidation of self-reported chronic conditions and health services in a managed care population1
Introduction
T elephone surveys are widely used to collect information about the health characteristics of a population. Although the method is cost-effective and efficient, the validity of the information collected is often questioned. Overestimates of some screening procedures and underreporting of medical conditions and risk behaviors have been attributed to survey data.1, 2, 3, 4, 5, 6 However, studies also have shown reasonable estimates of disease prevalence7 and trends over time3 based on self-reports. Much of the validation research on self-reported data for use of screening procedures has focused on mammography and Pap tests.2, 3, 8, 9, 10, 11, 12, 13, 14 Some studies have shown that self-reported data for these screening tests are generally valid.8, 9 Reporting the date of the screening examination is more problematic,3, 8, 10, 11, 12 and self-reports may significantly overestimate the use of screening,2 especially among some minority populations.12, 13, 14
The Behavioral Risk Factor Survey (BRFS) is a population-based telephone survey that provides state health departments with data for estimating prevalence of disease risk factors and for use in preventive clinical services.15 Interview information from the BRFS and direct patient examination have been used in a few studies to validate self-reported risk factors for cardiovascular disease.4, 16, 17 However, a comprehensive comparison of BRFS data with medical record data has never been undertaken. Information about the validity of self-reports from a standardized survey like BRFS would be especially useful for health plans in developing performance and accountability measures for use in plan evaluation systems such as the Health Plan Employer Data and Information Set (HEDIS).18
For this study, we examined the validity of self-reported data for the prevalence of three chronic health conditions (hypertension, hypercholesterolemia, and diabetes) and for the use of six preventive health services (blood pressure screening, blood cholesterol screening, clinical breast examination, mammography, Pap test, and influenza immunization) by comparing telephone survey findings with respondents’ medical records in a managed care population.
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Methods
In 1993, the Colorado Department of Public Health and Environment collaborated with Kaiser Permanente of Colorado (KPC) to conduct a special BRFS. The 1993 BRFS instrument, including questions regarding whether each preventive service received was performed at KPC or at some other service delivery site, was administered by telephone to a random sample of the KPC managed care population aged >21 years who had been members of KPC for at least 1 year. The sample was stratified by six age and
Results
For the three health conditions, sensitivity was highest for hypertension (83% of respondents with a medical record of hypertension reported the condition on the survey), moderate for diabetes (73%), and lowest for hypercholesterolemia (59%) (Table 1). One third of the respondents who were not sure whether their blood cholesterol had ever been checked had a medical record of hypercholesterolemia (data not shown). Specificity was high for all three conditions, especially for diabetes (99% of
Discussion
We found that sensitivity and specificity for self-reported chronic conditions were more consistent than for self-reported use of preventive clinical services. Self-reports were reasonably accurate for several routine screening tests: blood pressure screening, blood cholesterol screening, mammography, and Pap test. Although sensitivity for preventive services was high, specificity was quite low for most of the measures. However, the low specificity estimates are partially explained by the small
Acknowledgements
This project was made possible in part through grants from the Centers for Disease Control and Prevention and the Kaiser Foundation Health Plan of Colorado.
Analytic assistance and support from the Council of State and Territorial Epidemiologists is acknowledged.
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