Pediatric acquired demyelinating syndromes: a nationwide validation study of the Danish National Patient Register.

objectiveTo validate the Danish National Patient Register's (NPR) diagnoses of pediatric acquired demyelinating syndromes (ADS) including multiple sclerosis (MS). STUDY DESIGN AND

settingWe identified ADS diagnostic groups using International Classification of Diseases (ICD) codes and reviewed medical records to validate the NPR diagnoses during 2008-2015.

resultsAmong 409 children in the study, 184 children had a validated and final ADS diagnosis after reviewing medical records as follows: optic neuritis (ON; n=46), transverse myelitis (TM; n=16), acute disseminated encephalomyelitis (ADEM; n=50), clinically isolated syndrome (CIS) including dissemination in space (CIS [DIS]) but not dissemination in time (n=6), neuromyelitis optica spectrum disorder (NMOsd; n=5), and MS (n=61). During the mean follow-up of 4.6 years, 33% of children initially diagnosed with monophasic ADS progressed to MS. Positive predictive value (PPV) was 0.71 (95% confidence interval [CI] =0.62-0.80) for ON, 0.64 (95% CI =0.43-0.82) for TM, 0.93 (95% CI =0.84-0.98) for MS, 0.27 (95% CI =0.19-0.35) for CIS, 0.43 (95% CI =0.10-0.82) for NMOsd, and 0.15 (95% CI =0.10-0.20) for ADEM. Assuming complete coverage for non-MS ADS, the sensitivity was 0.99 (95% CI =0.93-1.00) for ON, 0.83 (95% CI =0.36-1.00) for CIS (DIS), and 0.80 (95% CI =0.56-0.94) for TM, but only 0.58 (95% CI =0.43-0.72) for ADEM and 0.60 (95% CI =0.15-0.95) for NMOsd.

conclusionPPV was high for MS and considered acceptable for ON and TM; therefore, these ICD revision 10 (ICD-10) codes from the NPR are useful for epidemiological studies. Conversely, PPV was low for CIS and ADEM; NMOsd was inconclusive.