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

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 κ 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 κ 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.

Duke Scholars

Author Don W. Bradley Family Medicine and Community Health, Family Medicine