Self-reported health parameters compared with clinician measurements: methods in practice-based research

Journal Name: 
J Public Health Manag.Pract
CONTEXT: Self-reported health data are used by health insurance companies to assess risk. Most studies show underreporting compared with clinical measurements. OBJECTIVE: To compare self-reported height, weight, blood pressure, waist circumference, and dietary intake with registered dietitian's (RD's) measures of the same parameters. DESIGN: This is a secondary analysis of data collected in a larger study on the benefits of Medical Nutrition Therapy from an RD for overweight and obese patients when provided free of charge through an insurance benefit. SETTING: Participants completed a health risk assessment survey at home, from which the self-reported measures were extracted. The clinical measurements were taken by an RD in the office during a visit for Medical Nutrition Therapy. PARTICIPANTS: Participants were 81.4% female, with a mean body mass index of 35.0. All were insured and had a least 1 visit with an RD. MAIN OUTCOME MEASURE(S): Main outcomes were correlation between self-reported and RD-measured height, weight, body mass index, blood pressure, and waist circumference. Blood pressure was categorized as normal or high and the kappa statistic was used to examine category agreement between the 2 measures. Servings of food groups were compared between the 2 measures by examining cumulative percent within 0, 1, or 2 servings of the RD-measured value. RESULTS: The 2 measures of height and weight were highly correlated (0.974 and 0.986, respectively). Blood pressure was more weakly correlated and when categorized had low kappa scores, as did servings of food groups. CONCLUSIONS: Height and weight were more closely correlated than in previous studies. In an insured population enrolled in a weight management program, self-reported measures may be accurate for determining program impact. Blood pressure may be better collected categorically than continuously. The necessity of food intake assessment on a risk assessment should be reconsidered
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