Background The explosion of drug development for rheumatoid arthritis and the revolution of early aggressive therapy for the disease have fuelled the search for better approaches to establish cost-effectiveness in early arthritis (EA). Unfortunately consensus on the choice of utility instrument is still lacking.
Objectives We aimed to compare the EQ-5D and SF-6D, 2 indirect utility measures widely used to calculate quality-adjusted life-years (QALYs), in terms of their utility score changes, and QALYS gain obtained, in a large prospective cohort of patients with EA, according to different therapeutic strategies.
Methods – Patients: included in the French nationwide ESPOIR cohort of EA (at least 2 swollen joints for less than 6 months and suspicion of RA).
– Data available: SF-6D and EQ-5D utility measures were longitudinally assessed in 813 patients with EA (at baseline, 6 months, 1year). Bio-clinical variables and X-rays were also recorded.
– Analysis: The change in SF-6D and EQ-5D utility scores and the QALYS gain obtained according to each utility measure change at 1 year (area under the curve (AUC) of the change in utility score between baseline and 6 months + AUC of the change in utility score between 6 and 12 months) were calculated and compared using paired t-test for the entire sample. This analysis was also conducted in patients treated by methotrexate (MTX) within the first 3 months without biological treatment.
Results 813 patients were included: mean age=48.1±12.6 years, 76.7% were female, mean DAS28=5.11±1.31; 372 patients (45.8%) were RF-positive and 315 (38.8%) were ACPA-positive.
At 12 months, the majority of patients had improved (91.4%): mean DAS change= -1.95 (SD=1.5). Whereas the distribution of utility scores was bimodal for the EQ-5D and near normal for the SF-6D, the distribution of utility change was almost normal for both. The EQ-5D provided larger absolute mean change estimates with greater change variance than the SF-6D: 0.154±0.315 for EQ-5D vs 0.095±0.129 for SF-6D at 1 year.
Regarding the 313 patients treated by MTX within the first 3 months without biological treatment, the mean QALYs gain for the EQ-5D was 0,118±0,213 and for the SF-6D=0,071±0,082 with a significant difference of 0,050±0,190 QALYs in favour of EQ-5D (70% more QALYs gained than with SF-6D) (p<0.0001).
Conclusions The high mean change of the EQ-5D compared to the SF-6D has consequences for cost-effectiveness analyses. In this example, the change estimated with the EQ-5D would result in a cost per QALY gained 40% lower than the cost per QALY gained calculated with the SF-6D. Furthermore, the smaller variance of the SF-6D would result in less uncertainty in estimating the relative cost-effectiveness of 2 treatments. The SF-6D may be more appropriate for use in RCTs of treatments for EA patients.
Disclosure of Interest : None declared
Statistics from Altmetric.com
If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.