Association between under-dose of enzyme replacement therapy and quality of life in adults with late-onset Pompe disease in China: A retrospective matched cohort study

Background Due to the high cost of enzyme replacement therapy (ERT), most of adults with late-onset Pompe disease (LOPD) who received ERT used the medication with insufficient dosefs in China. Objective To compare the change in quality of life (QoL) between adults with LOPD receiving underdose ERT and no ERT, and identify factors associated with the change of QoL. Methods A retrospective matched cohort study was conducted among adult patients with LOPD in a nationwide Pompe registry in China. Eligible participants were those who completed two investigations, and didn’t expose to ERT at baseline or before. The treated group were those who used ERT during follow-up; the untreated group received general care. The treated and untreated group were matched with a ratio of 1:2. QoL was assessed by the SF-12 and EQ-5D-5L. The dose of ERT was evaluated by the ratio of actual vials patients used divided by the indicated vials patients should use. The treated patients were further classified into mild and severe under-dose users by the median ratio. Multivariate linear regression analyses were performed to estimate the average treatment effect in the treated groups and identify factors associated with the changes of QoL scores. Results The study sample included 5 mild under-dose users, 6 severe under-dose users, and 22 untreated participants. Compared with the untreated group, mild under-dose ERT had no significant effect on the changes of QoL scores. In contrast, severe under-dose ERT was associated with a decline of physical QoL (β = -6.19, p = 0.001), but an increase of overall health state (β = 19.69, p = 0.032). A higher score of physical QoL (β = -0.74, p = 0.001) and overall health state (β = -0.69, p<0.001) at baseline was associated with decline in corresponding scores at follow-up. Being female was a contributor to the worsening of the overall health state (β = -22.79, p = 0.002), while being employed or at school was a predictor of improvement in mental QoL (β = 5.83, p = 0.002). Conclusions A Pompe-disease specific instrument based on patient experiences is warranted to closely monitor changes in QoL on a routine basis. It is desirable for patients with severe underdose ERT to discuss with physicians whether to adjust treatment strategies.