Mapping naso-ocular symptom scores to EQ-5D-5L utility values in Japanese cedar pollinosis

The total naso-ocular symptom score (TSS) is widely used as an endpoint to evaluate the severity of seasonal allergic rhinitis. However, it is not a generic preference-based measure. We sought to develop an algorithm for mapping between the TSS and health utility in Japanese cedar pollinosis (JCP). We also performed a cost-utility analysis of sublingual immunotherapy (SLIT) for JCP by using this algorithm. Patients with JCP filled out the TSS questionnaire and EQ-5D-5L simultaneously during the pollen season in 2019 and in 2020. We estimated a direct utility mapping model by regressing responses to individual TSS questions directly onto utility. The incremental cost-effectiveness ratio (ICER) of active SLIT to a placebo was determined by examining the drug expense and the estimated quality-adjusted life year (QALY) using a dataset from a double-blind placebo-controlled clinical trial. A total of 238 records were included for analysis. The estimated utility decreased with increasing severity of rhinitis. Patients with comorbid asthma showed lower utility. A negative and significant correlation was seen between the TSS and utility in both 2019 and 2020. The estimated equations were: Y(utility) = −0.0161∗X(TSS) + 1.005 in non-asthmatic JCP patients. The ICER of active SLIT to the placebo was estimated to be 4,049,720 and 6,011,218 JPY/QALY in the first and second year, respectively. It is possible to reasonably predict utility from the total naso-ocular symptom score by using regression models. In the estimated algorithm, pre-seasonal SLIT for JCP is cost-effective.