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Objective: To explore the correlation between submaximal exercise measurements and peak oxygen uptake in patients with pulmonary arterial hypertension (PAH)., Methods: The clinical data were retrospectively analyzed for 106 patients with PAH from Affiliated Shanghai Pulmonary Hospital, Tongji University from October 2010 to October 2013. The examinations included routine pulmonary function test, N-terminal pro-brain natriuretic peptide (NT-proBNP), 6-minute walk test, right heart catheterization and cardiopulmonary exercise testing. And within the same period, matched 20 healthy subjects without smoking and cardiopulmonary diseases were selected as control group., Results: Peak oxygen uptake (P-VO2), anaerobic threshold (AT), oxygen uptake efficiency slope (OUES) and oxygen uptake efficiency plateau (OUEP) were significantly lower in patients with PAH than control group ((841 ± 257) vs (1 682 ± 284) ml/min, (661 ± 171) vs (1 041 ± 243) ml/min, 1.1 ± 0.4 vs 2.3 ± 0.4, 25.8 ± 5.2 vs 35.5 ± 4.0, respectively) (all P < 0.001). And the predicted parametric values (%pred) were also lower in PAH group than control group (all P < 0.001). While the lowest ventilation (VE)/CO2 output (VCO2) (L-VE/VCO2) and VE/VCO2 slope were significantly higher in PAH group than control group (50.5 ± 15.9 vs 30.5 ± 3.0 and 57.2 ± 23.2 vs 25.6 ± 2.8, both P < 0.001). Pearson correlation analysis showed, except for VE/VCO2 slope%pred, AT%pred, L-VE/VCO2%pred, OUES%pred and OUEP%pred were correlated with P-VO2 (all P < 0.001). According to multiple linear regression analysis, only AT%pred and OUES%pred were the independent predictors of P-VO2 (β = 0.394, 0.384, both P < 0.001) and OUES%pred might be better than AT%pred (the adjusted β = 0.674). When AT%pred < 58.0% or OUES%pred < 65.0%, exercise capacity in PAH declined obviously with the sensitivity was 92.3% and 96.2% and the specificity 81.2% and 75.5% respectively., Conclusions: Exercise capacity in patients with PAH is significantly lower than healthy subjects. OUES%pred and AT%pred may be used as an independent predictor of exercise capacity. And OUES%pred may be more powerful.