National data with high validity and completeness showed that only 0.04% of Danish children had been registered with diagnosed hypertension

AIM: Hypertension has been reported in up to 4.0% of American children, but no national data exist in Europe. We studied the frequency of registered hypertension in Danish children and evaluated the data. METHODS: This 2014-2015 study focused on patients under the age of 16 registered with hypertension in the Danish National Patient Register and 10 paediatric departments in central and eastern Denmark. The diagnoses were coded according to the International Classification of Diseases, 10th revision. All the subjects' medical records were reviewed, including any confirmed diagnoses. RESULTS: There were 55 784 children under 16 in the study regions at 30 April 2014. By May 2015, 222 of those had been registered with hypertension: 200 in the Danish National Patient Register and 191 in the 10 paediatric departments. Their medical records confirmed hypertension in 187 and 185 cases, respectively. The prevalence of registered and confirmed hypertension was 222/553 784 (0.04%). The positive predictive values of hypertension were 187/200 (94%) and 185/191 (97%), and the completeness of diagnosed hypertension was 187/222 (84%) and 185/222 (83%). CONCLUSION: The registers had high-quality positive predictive values and completeness, but only 0.04% of the Danish children were registered with a verified diagnosis of hypertension.