Regional disparities in interferon therapy for chronic hepatitis C in Japan: a nationwide retrospective cohort study

BACKGROUND: Many patients with chronic hepatitis C have been treated with interferon (IFN) therapy in Japan, especially after the introduction of subsidies for medical expenses in 2008. However, its performance and outcome have never been evaluated. Therefore, a nationwide, mail-based, retrospective cohort study was conducted. METHODS: Regional disparities in the demographic features, treatment performance, and virological response were evaluated using an intent-to-treat design. The participating prefectures were classified into nine regions from north to south (Hokkaido/Tohoku, Kanto, Shin-etsu, Hokuriku, Tokai, Kinki, Chugoku, Shikoku, and Kyushu). Multivariate logistic regression analysis was performed to select predictive factors for treatment performance and outcome. RESULTS: From December 2009 to May 2013, 16,854 patients with chronic hepatitis C were registered from 37 prefectures in Japan (median age: 60 years; 50.4 % male; 74.8 % IFN-naïve; HCV genotype [1 or 2]/viral load [high (≥5 log IU/mL) or low (<5 log IU/mL)]: 1/high = 58.2 %, 1/low = 5.2 %, 2/high = 27.3 %, 2/low = 7.5 %; 83.4 % treated with peginterferon-α and ribavirin). Mean age, proportion of elderly patients (≥65 years), male sex, IFN-experienced, and HCV genotype were significantly different among the nine regions (all P < 0.001). Regional disparities were independently selected as one of the predictive factors for treatment performance and outcome in patients treated with peginterferon-α and ribavirin, which revealed two regions that required further investigation. CONCLUSIONS: Regional disparities still exist in IFN therapy, and are strongly associated with treatment performance and outcome. Since the accessibility to medical resources for individual patients seemed to be different among the nine regions, public health actions should be focused on how to construct and properly manage consultation networks between base hospitals and local clinics, especially in those regions with low population density. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12889-015-1891-2) contains supplementary material, which is available to authorized users.