Coagulation assays. When CTEPH is suspected, coagulopathy can be assessed by measuring anticardiolipin antibodies, lupus anticoagulant, and anti-b-2-glycoprotein antibodies.13
Chest CT will show radiographic findings in greater detail. An enlarged pulmonary artery (diameter ≥ 29 mm) or a ratio ≥ 1 of the diameter of the main pulmonary artery to the diameter of the ascending aorta is suggestive of PH.
Other tests. Overnight oximetry and testing for sleep-disordered breathing, performed in an appropriate setting, can be considered.13,14,19
Pulmonary function testing with diffusion capacity for carbon monoxide, high-resolution chest CT, and a 6-minute walk test (6MWT) can be considered in patients who have risk factors for chronic lung disease. Pulmonary function testing, including measurement of the diffusing capacity of the lungs for carbon monoxide, arterial blood gas analysis, and CT, is used to aid in interpreting echocardiographic findings in patients with lung disease in whom PH is suspected.
Testing for comorbidities. A given patient’s predisposing conditions for PH might already be known; if not, laboratory evaluation for conditions such as sickle cell disease, liver disease, thyroid dysfunction, connective tissue disorders (antibody tests of antinuclear antibody, rheumatoid factor, anticentromere, anti-topoisomerase, anti-RNA polymerase III, anti-double stranded DNA, anti-Ro, anti-La, and anti-U1-RNP), and vasculitis (anti-neutrophil cytoplasmic autoantibodies) should be undertaken.
Analysis of stool and urine for Schistosoma spp parasites can be considered in an appropriate clinical setting.13
Right heart catheterization. Once alternative diagnoses are excluded, RHC is recommended to make a definitive diagnosis and assess the contribution of left heart disease. Vasoreactivity—defined as a reduction in mPAP ≥ 10 mm Hg to reach an absolute value of mPAP ≤ 40 mm Hg with increased or unchanged cardiac output—is assessed during RHC by administering nitric oxide or another vasodilator. This definition of vasoreactivity helps guide medical management in patients with PAH.7,20
