Long-term cost and utility consequences of short-term clinically important deterioration in patients with chronic obstructive pulmonary disease: results from the TORCH study

Abstract

Purpose: Clinically important deterioration (CID) in chronic obstructive pulmonary disease (COPD) is a novel composite endpoint that assesses disease stability. The association between short-term CID and future economic and quality of life (QoL) outcomes has not been previously assessed. This analysis considers 3-year data from the TOwards a Revolution in COPD Health (TORCH) study, to examine this question. Patients and methods: This post hoc analysis of TORCH (NCT00268216) compared costs and utilities at 3 years among patients without CID (CID-) and with CID (CID+) at 24 weeks. A positive CID status was defined as either: a deterioration in forced expiratory volume in 1 second (FEV₁) of ≥100 mL from baseline; or a ≥4-unit increase from baseline in St George's Respiratory Questionnaire (SGRQ) total score; or the incidence of a moderate/severe exacerbation. Patients from all treatment arms were included. Utility change was based on the EQ-5D utility index. Costs were based on healthcare resource utilization from 24 weeks to end of follow-up combined with unit costs for the UK (2016 GBP), and reported as per patient per year (PPPY). Adjusted estimates were generated controlling for baseline characteristics, treatment assignment, and number of CID criteria met. Results: Overall, 3,769 patients completed the study and were included in the analysis (stable CID- patients, n=1,832; unstable CID+ patients, n=1,937). At the end of follow-up, CID- patients had higher mean (95% confidence interval [CI]) utility scores than CID+ patients (0.752 [0.738, 0.765] vs 0.697 [0.685, 0.71]; difference +0.054; P<0.001), and lower costs PPPY (£538 vs £916; difference: £378 [95% CI: £244, £521]; P<0.001). The cost differential was primarily driven by the difference in general hospital ward days (P=0.003). Conclusion: This study demonstrated that achieving early stability in COPD by preventing short-term CID is associated with better preservation of future QoL alongside reduced healthcare service costs.

Keywords: EQ-5D; direct medical costs; resource utilization; utilities.

Figure 1

Study design. Abbreviation: CID, clinically important deterioration.

Figure 2

Patient disposition. Abbreviations: CID, clinically important deterioration; COPD, chronic obstructive pulmonary disease; EQ-5D, EuroQol 5-dimensional scale; TORCH, TOwards a Revolution in COPD Health.

Figure 3

Total direct costs PPPY* (2016 GBP)^† by CID status, for all treatments (A) and by individual treatment (B). *Cost data are presented to three significant figures for values of four figures or more and to the nearest pound for values of three figures or less; ^†adjusted using a two-part modeling approach, where a logistic regression was run to predict the likelihood of having costs >0, followed by a generalized linear model (gamma distribution with a log link) run for patients with positive costs. The results of these two models were then used to calculate predicted cost estimates for each patient. 95% CIs were generated using 5,000 bootstrapped samples (sampling with replacement). Analysis of complete cases was weighted by the inverse probability of being a complete case. Abbreviations: CI, confidence interval; CID, clinically important deterioration; FP, fluticasone propionate; GBP, Great British Pounds; PPPY, per patient per year; SAL, salmeterol.

Figure 4

EQ-5D score by time and CID status at Week 24 and 3 years. *EQ-5D was administered in only a subset of countries participating in the TORCH study. Abbreviations: CID, clinically important deterioration; EQ-5D, EuroQol 5-dimensional scale; TORCH, TOwards a Revolution in COPD Health.