Geographical and socioeconomic differences in compliance with and access to allergen immunotherapy in Denmark: A nationwide registry-based study - 1998-2016

BACKGROUND: Allergen immunotherapy (AIT) is a cost-effective treatment option in moderate-severe allergic rhino-conjunctivitis. Inequality in access to AIT and variation in compliance related to socioeconomic status or geographical location have not been described previously.

OBJECTIVE: The aim of the study was to evaluate access to grass pollen AIT at various educational attainment levels in the five regions of Denmark. Furthermore, grass pollen AIT treatment compliance was evaluated with respect to age, educational attainment and geographical area.

METHODS: The unique civil registration number of every citizen in Denmark was combined with the nationwide Danish National Health Service Prescription Database and Statistics Denmark Database to extract age, gender, residence and educational attainment of every citizen who collected prescribed AIT medication from 1998 to 2016. Then, compliance and use of AIT were calculated with respect to age, geographical location and educational attainment.

RESULTS: The use of subcutaneous AIT (SCIT) was significantly higher in the Capital Region; this difference was less predominant for sublingual AIT (SLIT). People who were educated only to primary school or vocational training levels were less frequent users of AIT. Compliance was especially low in the Capital Region and among people educated only to primary school level. In the age groups, compliance was similar, apart from SLIT users aged 0-9, for whom compliance was higher.

CONCLUSION: This nationwide study finds that SLIT has the potential to reduce inequality in access to AIT. A focus intervention is needed to facilitate access to and compliance with AIT in groups with lower socioeconomic status.