Cathrine Wildenschild,1 Frank Mehnert,1 Reimar Wernich Thomsen,1 Helle Klingenberg Iversen,2 Karsten Vestergaard,3 Annette Ingeman,1 Søren Paaske Johnsen11Department of Clinical Epidemiology, Aarhus University Hospital, Aarhus, 2Department of Neurology, Glostrup Hospital, Glostrup, 3Department of Neurology, Aalborg Hospital, Aarhus University Hospital, Aalborg, DenmarkBackground: The validity of the registration of patients in stroke-specific registries has seldom been investigated, nor compared with administrative hospital discharge registries. The objective of this study was to examine the validity of the registration of patients in a stroke-specific registry (The Danish Stroke Registry [DSR]) and a hospital discharge registry (The Danish National Patient Registry [DNRP]).Methods: Assuming that all patients with stroke were registered in either the DSR, DNRP or both, we first identified a sample of 75 patients registered with stroke in 2009; 25 patients in the DSR, 25 patients in the DNRP, and 25 patients registered in both data sources. Using the medical record as a gold standard, we then estimated the sensitivity and positive predictive value of a stroke diagnosis in the DSR and the DNRP. Secondly, we reviewed 160 medical records for all potential stroke patients discharged from four major neurologic wards within a 7-day period in 2010, and estimated the sensitivity, specificity, positive predictive value, and negative predictive value of the DSR and the DNRP.Results: Using the first approach, we found a sensitivity of 97% (worst/best case scenario 92%-99%) in the DSR and 79% (worst/best case scenario 73%-84%) in the DNRP. The positive predictive value was 90% (worst/best case scenario 72%-98%) in the DSR and 79% (worst/best case scenario 62%-88%) in the DNRP. Using the second approach, we found a sensitivity of 91% (95% confidence interval [CI] 81%–96%) and 58% (95% CI 46%–69%) in the DSR and DNRP, respectively. The negative predictive value was 91% (95% CI 83%–96%) in the DSR and 72% (95% CI 62%–80%) in the DNRP. The specificity and positive predictive value did not differ among the registries.Conclusion: Our data suggest a higher sensitivity in the DSR than the DNRP for acute stroke diagnoses, whereas the positive predictive value was comparable in the two data sources.Keywords: diagnosis, sensitivity, specificity, registries