Pulmonary function vascular index predicts prognosis in idiopathic interstitial pneumonia

Background and objective: Pulmonary hypertension (PH) is associated with increased mortality in fibrotic idiopathic interstitial pneumonia (IIP). We hypothesize that baseline K_CO (diffusing capacity of carbon monoxide/alveolar volume) and 6‐month decline in K_CO reflect PH, thus predicting mortality in IIP. Methods: All IIP referrals (2004–2007) were identified (n = 269). 192 had pulmonary function at 6 months. Fifty‐two (27%) died during follow‐up (median 22.5 months). Outcome was evaluated for early (1 year from 6‐month pulmonary function) and overall mortality. A vascular index best predicting mortality was identified (using baseline and 6‐month decline in K_CO) and evaluated against PH at echocardiography. Results: Baseline and 6‐month decline in K_CO were associated with early and overall mortality. A positive vascular index (baseline K_CO% ≤ 50% and/or ≥15% decline in K_CO at 6 months; n = 40) was strongly predictive of early and overall mortality. Neither a diagnosis of idiopathic pulmonary fibrosis nor PH predicted early death when incorporated into this model. In patients without baseline PH, with follow‐up echocardiography (n = 60), a positive vascular index was associated with PH at follow‐up. Conclusions: A vascular index comprised of baseline and 6‐month decline in K_CO strongly predicted increased mortality and development of PH on echocardiography. In, K_CO may be an important marker for pulmonary vascular disease and its associated mortality.