How do you clinically distinguish between group I and group III PH in patients with CTD-ILD?

The distinction between pulmonary hypertension (PH) of the group 1 (pulmonary arterial hypertension (PAH)) and group 3 (pulmonary hypertension (PH) due to lung disease and/or hypoxia) is essential since the management is different. In group 1 PH we stratify the risk and treat with a variety of PAH-s...