Table 1.

Schema for classification of pulmonary hypertension in veterans by ICD-9 diagnosis code usage.

PH Grouping Designation	Included ICD-9Codes
Group 1, PAH	416.0, 416.2, 416.8, 416.9 (Excluded if meeting any of the below)
Group 2, PH due to left heart disease	402.01, 402.11, 402.91, 404.01, 404.03, 404.11, 404.13, 404.91, 404.93, 428.xx
Group 3, PH due to lung diseases and/or hypoxemia	490.xx–496.xx, 500.xx–508.xx, 515.xx, 516.xx, 517.1, 517.2, 327.23
Group 4, chronic thromboembolic PH	416.2
Group 5, PH with unclear multifactorial mechanisms	282.0x, 282.4x, 282.6x, 271.xx, 272.7
Multiple causes, unclassifiable	Patients with ICD-9 diagnosis codes included in more than 1 of Groups 2, 3, 4, and/or 5 above

ICD-9 codes of 416.0, 416.2, 416.8, 416.9 were required to be present for inclusion. PAH, pulmonary arterial hypertension; PH, pulmonary hypertension.