Estimation of minimal clinically important change of the Japanese version of EQ-5D in patients with chronic noncancer pain: a retrospective research using real-world data

BACKGROUND: Quality of life (QoL) is routinely assessed and evaluated in medical research. However, in Japan, there is a lack of solid cutoff criteria for evaluating QoL improvement in chronic noncancer pain management. The present study was conducted to identify the minimal clinically important change (MCIC) of the Japanese version of EuroQol-5D 3L(EQ-5D) utility score and numeric rating scale (NRS) with an emphasis on chronic noncancer pain. METHODS: The data source for this post hoc research was the post-marketing surveillance (PMS) data for a tramadol/acetaminophen combination tablet, which was previously conducted in real-world settings. The parameters extracted from the PMS data were sociodemographic characteristics, NRS, EQ-5D, and dichotomous physician’s global impression of treatment effectiveness (PGI). The optimal cutoff points of MCIC for EQ-5D utility and NRS scores were evaluated using receiver operating characteristics (ROC) analysis. An anchor-based approach using PGI was applied. RESULTS: Data of 710 patients with chronic noncancer pain were extracted from the PMS database. The NRS score decreased by 2.7 (standard deviation, 2.3) points, whereas the EQ-5D score increased by 0.16 (0.20) points at 4 weeks from baseline. The changes from baseline in NRS and EQ-5D were significantly correlated (r = 0.53, p < 0.001). The estimated optimal cutoff points of MCIC for EQ-5D and NRS were 0.10 and −2.0 points, respectively. The area under the curve of ROC was > 0.80 in both analyses. CONCLUSION: These results demonstrated novel cutoff criteria for the Japanese version of EQ-5D, focusing on patients with chronic noncancer pain. The obtained criteria were fairly consistent and can be confidently utilized as an evaluation tool in medical research on chronic noncancer pain in Japan, with additional functionality and usability for QoL assessment in pain management practice. TRIAL REGISTRATION: The data source of this post hoc research was a PMS study with the identifier number UMIN000015901 at umin.ac.jp, UMIN clinical trial registry (UMIN-CTR).