The national incidence of PML in Sweden, 1988-2013.

OBJECTIVE: To investigate the incidence of progressive multifocal leukoencephalopathy (PML) and patient characteristics in Sweden between 1988 and 2013. METHODS: All PML diagnoses in Sweden between 1988 and 2013 were identified in the National Patient Register. Information to validate the diagnosis and patient characteristics was obtained from medical records. RESULTS: Medical record review classified 108 out of 250 patients (43%) as definite (n = 84), probable (n = 4), or possible (n = 20) PML according to diagnostic criteria. Accurate diagnoses were more common in records obtained from neurology departments (82% of patients seen in neurology departments) compared with other departments (31%) (p < 0.001). The incidence of PML increased from a largely stable level at 0.026 (95% confidence interval [CI] 0.021-0.031) per 100,000 individuals per year during 1988-2010 to 0.11 (95% CI 083-0.137) during 2011-2013, during which time there was a notable increase (p < 0.001). Hematologic malignancies (n = 34), HIV/AIDS (n = 33), and autoimmune disease (n = 23) were the most common underlying diseases. Treatment with a monoclonal antibody prior to PML diagnosis was identified in 26 patients. CONCLUSION: An increased incidence of PML in Sweden was observed and coincided with the prior use of monoclonal antibody treatment. The high level of misdiagnosis emphasizes the importance of immediate contact with a neurology center upon suspicion of PML.

Use of palivizumab is underestimated in the Swedish Prescribed Drug Register - implications for register-based drug studies.

BACKGROUND: Register studies are a valuable tool, when monitoring the safety of drugs. The Swedish Prescribed Drug Register (PDR) was established in 2005 and keeps records of all prescribed drugs dispensed in community pharmacies. Drugs prescribed in-hospital are not registered on an individual level, which may hamper the validity of register-based studies on drugs potentially administered in-hospital. OBJECTIVE: The objective was to assess the ability of the PDR to identify children treated with the monoclonal antibody palivizumab, which is used for prophylaxis against respiratory syncytial virus (RSV) infection in children. METHODS: Palivizumab exposure as filled prescriptions recorded in the PDR was assessed by indication of treatment (preterm-born children, bronchopulmonary dysplasia, or hemodynamically significant heart disease) and presented as numbers and proportions. For a random sample of children with an indication for treatment and without record of palivizumab exposure in the drug register, numbers and proportions by indication of treatment as noted in medical records were presented. The extent of underreporting in the drug register was estimated by indication for treatment. RESULTS: Through the national health registers, 2,317 children were identified as being at risk for severe infection with RSV infection and 75% had no records indicating palivizumab exposure in the PDR. In a random sample of 176 children at high risk for RSV infection and with no records of palivizumab prescription fills in the PDR, 47% had been treated with palivizumab according to medical records. The PDR underestimated palivizumab treatment with 49% in children born preterm, 42% in children with bronchopulmonary dysplasia, and 23% in those with a hemodynamically significant heart disease. CONCLUSION: Our findings underline the need of improving the information in the Swedish national registers concerning drugs administered in-hospital.