Longitudinal predictive ability of mapping models: examining post-intervention EQ-5D utilities derived from baseline MHAQ data in rheumatoid arthritis patients.

Abstract

OBJECTIVES:

The purpose of this methodological study was to to provide insight into the under-addressed issue of the longitudinal predictive ability of mapping models. Post-intervention predicted and reported utilities were compared, and the effect of disease severity on the observed differences was examined.

METHODS:

A cohort of 120 rheumatoid arthritis (RA) patients (60.0% female, mean age 59.0) embarking on therapy with biological agents completed the Modified Health Assessment Questionnaire (MHAQ) and the EQ-5D at baseline, and at 3, 6 and 12 months post-intervention. OLS regression produced a mapping equation to estimate post-intervention EQ-5D utilities from baseline MHAQ data. Predicted and reported utilities were compared with t test, and the prediction error was modeled, using fixed effects, in terms of covariates such as age, gender, time, disease duration, treatment, RF, DAS28 score, predicted and reported EQ-5D.

RESULTS:

The OLS model (RMSE = 0.207, R(2) = 45.2%) consistently underestimated future utilities, with a mean prediction error of 6.5%. Mean absolute differences between reported and predicted EQ-5D utilities at 3, 6 and 12 months exceeded the typically reported MID of the EQ-5D (0.03). According to the fixed-effects model, time, lower predicted EQ-5D and higher DAS28 scores had a significant impact on prediction errors, which appeared increasingly negative for lower reported EQ-5D scores, i.e., predicted utilities tended to be lower than reported ones in more severe health states.

CONCLUSIONS:

This study builds upon existing research having demonstrated the potential usefulness of mapping disease-specific instruments onto utility measures. The specific issue of longitudinal validity is addressed, as mapping models derived from baseline patients need to be validated on post-therapy samples. The underestimation of post-treatment utilities in the present study, at least in more severe patients, warrants further research before it is prudent to conduct cost-utility analyses in the context of RA by means of the MHAQ alone.

• Authors: Nick Kontodimopoulos, Panagiotis Bozios, John Yfantopoulos, Dimitris Niakas
• Journal: The European journal of health economics : HEPAC : health economics in prevention and care (Eur J Health Econ) Vol. 14 Issue 2 Pg. 307-14 (Apr 2013) ISSN: 1618-7601 [Electronic] Germany
• PMID: 22252308 (Publication Type: Journal Article)

Chemical References

• Antirheumatic Agents

Topics

• Antirheumatic Agents (economics, therapeutic use)
• Arthritis, Rheumatoid (drug therapy)
• Cohort Studies
• Female
• Humans
• Male
• Middle Aged
• Models, Economic
• Outcome Assessment, Health Care
• Predictive Value of Tests
• Quality of Life
• Regression Analysis
• Severity of Illness Index