Ann Haerskjold, Lonny Henriksen, Susanne Way, Mikkel Malham, Jesper Hallas, Lars Pedersen, Lone Graff Stensballe

National prescription databases are important tools in pharmacoepidemiological studies investigating potential long-term adverse events after drug use. Palivizumab is a biological pharmaceutical used as passive prophylaxis against severe infection with respiratory syncytial virus in high-risk children. To assess the registration of palivizumab in the Danish National Prescription Registry (DNPR) and to examine if palivizumab reimbursement data obtained from the Danish Health and Medicines Authority could serve as a supplement to data from the DNPR. Registration of palivizumab exposure in the DNPR between 1999 and 2010 was compared to two external data sources: registration of palivizumab exposure in medical records, and palivizumab reimbursement data. During the study period, 182 children with palivizumab exposure were registered in the DNPR. A total of 207 children were registered for palivizumab reimbursement. The sensitivity of palivizumab registration in the DNPR was 26% (20%-34%), and the specificity of no palivizumab registration in the DNPR was 97% (94%-99%), with data from the medical record as the reference. Palivizumab registration sensitivity in reimbursement data was 29% (22%-36%), and the specificity of no palivizumab registration in the DNPR was 97% (94%-99%), with data from the medical record as the reference. Exposure to palivizumab was underestimated in the DNPR. Reimbursement data are a readily accessible data supplement, which only slightly increased the sensitivity of palivizumab registration in the DNPR. Our findings underline the need to improve DNPR information concerning drugs administered in hospitals.