International Classification of Diseases Coding Changes Lead to Profound Declines in Reported Idiopathic Pulmonary Arterial Hypertension Mortality and Hospitalizations

Sudden shifts in reported IPAH mortality and hospital discharges were seen in all databases, likely related to coding changes. These findings raise questions about the accuracy of pulmonary hypertension diagnosis codes. Studies based on International Classification of Diseases, Ninth Revision and International Classification of Diseases, 10th Revision codes may have inadvertently included patients with other forms of pulmonary hypertension and should be reevaluated in this context. Validation studies of the IPAH diagnosis code are needed, and changes to the ICD coding system should be considered.