Improving the detection of pulmonary hypertension in systemic sclerosis using pulmonary function tests

Area of Science:

• Pulmonary Medicine
• Cardiology
• Rheumatology

Background:

• Systemic sclerosis (SSc) is associated with a high risk of pulmonary hypertension (PH).
• Accurate patient selection for right-sided heart catheterization (RHC) is crucial for diagnosing PH in SSc patients.
• Pulmonary function tests (PFTs) offer a non-invasive method to assess lung function.

Purpose of the Study:

• To develop a practical formula for predicting mean pulmonary artery pressure (mPAP) in SSc patients using PFT results.
• To improve the selection process for RHC in SSc patients based on PFT-derived predictions.
• To stratify SSc patients into low, average, and high risk groups for PH.

Main Methods:

• A formula was derived using data from 257 SSc patients undergoing RHC.
• The formula predicts mean pulmonary artery pressure (mPAP) using SpO₂ (oxygen saturation) and DLCO % predicted (diffusing capacity for carbon monoxide).
• The formula was validated in a separate cohort of 129 SSc patients.

Main Results:

• The derived formula is: predicted mPAP = 136 - SpO₂ - 0.25 × DLCO % predicted.
• Validation showed an area under the curve of 0.75, indicating good diagnostic value.
• The formula effectively stratified patients into PH risk groups: low (<25 mm Hg), average (25-35 mm Hg), and high (>35 mm Hg).

Conclusions:

• An easily applicable formula using PFTs can predict PH prevalence in SSc patients.
• This formula complements echocardiography and enhances the selection of patients for RHC.
• The formula aids in identifying SSc patients who would benefit from further investigation for pulmonary hypertension.