Lung disease severity in idiopathic pulmonary fibrosis is more strongly associated with impedance measures of bolus reflux than pH parameters of acid reflux alone

Background Gastroesophageal reflux (GER) has been associated with idiopathic pulmonary fibrosis (IPF). Pathogenesis may be related to chronic micro‐aspiration. We aimed to assess objective measures of GER on multichannel intraluminal impedance and pH study (MII‐pH) and their relationship with pulmonary function testing (PFT) results, and to compare the performance of pH/acid reflux parameters vs corresponding MII/bolus parameters in predicting pulmonary dysfunction in IPF. Methods This was a retrospective cohort study of IPF patients undergoing prelung transplant evaluation with MII‐pH off acid suppression, and having received PFT within 3 months. Patients with prior fundoplication were excluded. Severe pulmonary dysfunction was defined using diffusion capacity of the lung for carbon monoxide (DLCO) ≤40%. Six pH/acid reflux parameters with corresponding MII/bolus reflux measures were specified a priori. Multivariate analyses were applied using forward stepwise logistic regression. Predictive value of each parameter for severe pulmonary dysfunction was calculated by area‐under‐the‐receiver‐operating‐characteristic‐curve or c‐statistic. Key Results Forty‐five subjects (67% M, age 59, 15 mild‐moderate vs 30 severe) met criteria for inclusion. Patient demographics and clinical characteristics were similar between pulmonary dysfunction groups. Abnormal total reflux episodes and prolonged bolus clearance time were significantly associated with pulmonary dysfunction severity on univariate and multivariate analyses. No pH parameters were significant. The c‐statistic of each pH parameter was lower than its MII counterpart in predicting pulmonary dysfunction. Conclusions & Inferences MII/bolus reflux, but not pH/acid reflux, was associated with pulmonary dysfunction in prelung transplant patients with IPF. MII‐pH may be more valuable than pH testing alone in characterizing GER in IPF. Gastroesophageal reflux (GER) has been associated with idiopathic pulmonary fibrosis (IPF). We assessed objective measures of GER and their relationship with lung disease severity measured on pulmonary function testing (PFT) in IPF patients. Abnormal bolus reflux as measured on multichannel intraluminal impedance (MII) is associated with more severe dysfunction on PFT. MII parameters of reflux also more strongly correlate with lung disease severity than pH‐only measures of acid reflux. MII‐pH may be valuable in characterizing GER and help guide IPF management.