Outcomes, health policy, and managed care: relationships between patient-reported outcome measures and clinical measures in outpatients with heart failure

Abstract

Background: Patient-reported outcomes are increasingly used to assess the efficacy of new treatments. Understanding relationships between these and clinical measures can facilitate their interpretation. We examined associations between patient-reported measures of health-related quality of life and clinical indicators of disease severity in a large, heterogeneous sample of patients with heart failure.

Methods: Patient-reported measures, including the Kansas City Cardiomyopathy Questionnaire (KCCQ) and the EuroQol Visual Analog Scale (VAS), and clinical measures, including peak VO(2), 6-minute walk distance, and New York Heart Association (NYHA) class, were assessed at baseline in 2331 patients with heart failure. We used general linear models to regress patient-reported measures on each clinical measure. Final models included for significant sociodemographic variables and 2-way interactions.

Results: The KCCQ was correlated with peak VO(2) (r = .21) and 6-minute walk distance (r = .27). The VAS was correlated with peak VO(2) (r = .09) and 6-minute walk distance (r = .11). Using the KCCQ as the response variable, a 1-SD difference in peak Vo(2) (4.7 mL/kg/min) was associated with a 2.86-point difference in the VAS (95% CI, 1.98-3.74) and a 4.75-point difference in the KCCQ (95% CI, 3.78-5.72). A 1-SD difference in 6-minute walk distance (105 m) was associated with a 2.78-point difference in the VAS (95% CI, 1.92-3.64) and a 5.92-point difference in the KCCQ (95% CI, 4.98-6.87); NYHA class III was associated with an 8.26-point lower VAS (95% CI, 6.59-9.93) and a 12.73-point lower KCCQ (95% CI, 10.92-14.53) than NYHA class II.

Conclusions: These data may inform deliberations about how to best measure benefits of heart failure interventions, and they generally support the practice of considering a 5-point difference on the KCCQ and a 3-point difference on the VAS to be clinically meaningful.

Trial registration: ClinicalTrials.gov NCT00047437.

Figure 1. Side-by-Side Box Plot of the VAS and the KCCQ Overall Score by NYHA Class

The upper and lower bounds of the boxes represent interquartile ranges. The lines dividing the boxes represent medians and the points inside represent means. The upper ends of the whiskers represent maximum observations; the lower ends represent minimum observations (NYHA = 3) or minimum observations above the lower fence of 1.5 interquartile range below the 25th percentile (NYHA = 2); and the open points represent extreme observations below the lower fence.

Figure 2. Interaction Between Age and Peak VO₂ in Relationship With the KCCQ Physical Limitation Subscale

The solid lines represent predicted regression lines at the mean age (59 years, in red), 1 SD above the mean age (72 years, in blue), and 1 SD below the mean age (47 years, in green), with all categorical variables (ie, education level, annual income, employment status, marital status, and ethnicity) held at their modes. The dashed lines represent 95% confidence intervals around the fitted lines. β̂ denotes predicted slope.

Figure 3. Interaction Between Ethnicity and Peak VO₂ in Relationship With the KCCQ Physical Limitation Subscale

The solid lines represent predicted regression lines for patients of Hispanic or Latino ethnicity and for patients who are not Hispanic or Latino, with age held at the mean (59 years) and all categorical variables (ie, education level, annual income, employment status, and marital status) held at their modes. The dashed lines represent 95% confidence intervals around the fitted lines. β̂ denotes predicted slope.