Impact of influenza-like illnesses on health state utility value among Japanese children and adults.

Purpose: For future health technology assessment, an assessment of the utility value of influenza-like illnesses (ILIs) is crucial. Therefore, the objective of this study was to evaluate the impact of ILIs on utility value in a Japanese population.

Methods: We conducted an online survey between March and June 2024 to evaluate the impacts of ILIs on health-related quality of life, using a Japanese version of the EuroQol 5 Dimensions 5 Levels (EQ-5D-5 L) and EuroQol visual analog scale (EQ-VAS). Participants were children and adults aged < 80 years who experienced ILI symptoms or required home isolation due to a respiratory infection. A follow-up survey was conducted 2-3 weeks after the first survey to assess recovery. For children, we asked their parents or guardians to answer as the child's proxy. A generalized linear model was used to assess the impact of patient demographics, type and onset of symptoms and diagnosis on disutility.

Results: In total, 392 participants answered the first survey, and 264 participants answered the follow-up survey (134 adult participants and 130 parents or guardians). Compared with those who only answered the first survey, those who also answered the follow-up survey were older and more likely to be male in adult participants. The mean differences in the utility value and VAS scores between the first and follow-up surveys were - 0.055 and - 10.6 in the adult samples and - 0.079 and - 17.9 in the pediatric samples, respectively. In the generalized linear model, symptom onset within 7 days in the first survey was significantly associated with disutility value (coefficient - 0.049 [95% confidence interval [CI] - 0.086 to - 0.012], p = 0.010). However, none of the patient demographics were significantly associated with disutility value.

Conclusion: Utility values were lower during the symptomatic phase compared with the recovery phase. Our results are useful for disease burden assessment, health technology assessment, and cost-effectiveness analysis, which can support decision-making on the preventive and therapeutic management of respiratory infections.