Methods and Limitations
The prevalence of diabetes-related preventive care practices in the United States, including Puerto Rico, was determined by using data from the Behavioral Risk Factor Surveillance System (BRFSS). An ongoing, monthly telephone survey of the noninstitutionalized adult population in each state, the BRFSS provides self-reported, state-specific information on behavioral risk factors for disease and on preventive health practices. Respondents were considered to have diabetes if they responded yes to the question, Has a doctor ever told you that you have diabetes? Women who indicated that they only had diabetes during pregnancy were not considered to have diabetes. Responses to the following questions were used to determine the prevalence of diabetes-related preventive care practices among persons with diabetes:
- When was the last time you had an eye exam in which the pupils were dilated?
- About how many times in the last year has a health professional checked your feet for any sores or irritations?
- About how often do you check your blood for glucose or sugar?
- About how many times in the past 12 months have you seen a doctor, nurse, or other health professional for your diabetes?
- About how often do you check your feet for any sores or irritations?
- A test for hemoglobin A1c measures the average level of blood sugar over the past three months. About how many times in the past 12 months has a doctor, nurse, or other health professional checked you for hemoglobin A1c?
- Have you ever taken a course or class in how to mange your diabetes yourself?
- During the past 12 months, have you had a flu shot?
- Have you ever had a pneumonia vaccination?
Where feasible and in order to improve the precision of the estimates, 3-year averages were used to estimate the prevalence of preventive care practices. Not all states have complete data for each year of monitoring; therefore, each 3-year averaged estimate is composed of at least 2 years of data. Before 2001, the vaccination questions were included on the survey every other year, so 3-year averages were not used. National estimates of preventive care practices are based on single years of data.
Persons residing in nursing homes and in households without telephones are not included in this survey; therefore, these results cannot be generalized to those segments of the population. All data in the BRFSS are obtained by self-report and are subject to recall bias or may be underreported or overreported. Self-report of diabetes and self-report of socio-demographic characteristics are highly accurate.1, 2 Self-report of a dilated eye examination and influenza vaccine have been shown to have high accuracy as well.3–5 Self-report of A1c measurement has been shown to have a high sensitivity and low specificity.6 Further investigation of the reliability and validity of self-reported preventive care practices is needed.
- Bowlin SJ, Morrill BD, Nafziger AN, Lewis C, Pearson TA. Reliability and changes in validity of self-reported cardiovascular disease risk factors using dual response: the Behavioral Risk Factor Survey. J Clin Epidemiol 1996;49:511–517.
- Stein AD, Courval JM, Lederman RI, Shea S. Reproducibility of responses to telephone interviews: demographic predictors of discordance in risk factor status. Am J Epidemiol 1996;141:1097–1106.
- Will JC, German RR, Shurman E, Michael S, Kurth DM, Deeb L. Patient adherence to guidelines for diabetic eye care: results from the Diabetic Eye Disease Follow-up Study. Am J Public Health 1994;4:1669–1671.
- Hutchison BG. Measurement of influenza vaccination status of the elderly by mailed questionnaire: response rate, validity and cost. Can J Public Health 1989;80:271–275.
- MacDonald R, Baken L, Nelson A, Nichol KL. Validation of self-report of influenza and pneumococcal vaccination status in elderly outpatients. Am J Prev Med 1999;16(3):173–177.
- Briggs Fowles J, Rosheim K, Fowler EJ, Craft C, Arrichiello L. The validity of self-reported diabetes quality of care measures. Int J Qual Health Care 1999;11(5):407–412.