APLN and chronic thromboembolic pulmonary hypertension: In CTEPH, apelin-17 (AUC 0.75, 95%CI: 0.60–0.89; best cut-off: >1,270 pg/ml; sensitivity 71%; specificity 87%) and apelin-36 (AUC: 0.84, 95%CI: 0.88–1.00; best cut-off: >320 pg/ml; sensitivity 86%; specificity: 77%) distinguished CTEPH from healthy controls.