Oil red O stain of alveolar macrophages is an effective screening test for gastroesophageal reflux disease in lung transplant recipients

BACKGROUND: Gastroesophageal reflux disease (GORD) and microaspiration may be associated with lipid index; acute graft dysfunction and development of obliterative bronchiolitis (OB) after lung transplantation. The reflux disease; gold standard for diagnosis of GORD is the 24-hour esophageal pH-monitoring study, although no simple, lung transplant non-invasive screening test is routinely employed. Oil red O staining of alveolar macrophages in bronchoal-veolar lavage (BAL) fluid identifies exogenous lipid and may be a surrogate marker for microaspiration. In this study we aimed to assess the utility of the lipid index in identifying patients with significant GORD. METHODS: Our investigation was a prospective analysis of 34 lung transplant patients who were transplanted between April 1999 and July 2006 at a single institution. All patients with recurrent respiratory infections, recurrent acute rejection, unexplained graft dysfunction or newly diagnosed OB had Oil red O staining of alveolar macrophages on BAL specimens at bronchoscopy and 24-hour esophageal pH monitoring. A quantitative assessment called the lipid index was performed resulting in a score from 0 to 400. Abnormal 24-hour pH studies were defined as acid exposure >3.4% in the distal and/or >1% in the proximal esophageal site. RESULTS: Thirty-four patients with a mean age 36.1 years and mean post-operative day of 571 +/- 648 had lipid indices of 143 +/- 94 (range 3 to 341). Twenty-four-hour pH studies revealed a distal mean of 16.1 +/- 6.2% and proximal mean of 6.4 +/- 3.7%. A lipid index >150 was 82.3% sensitive and 76.4% specific for an abnormal 24-hour pH result. Foreign material present on cytology of bronchial fluid seen in 28% of patients showed poor correlation with Oil red O stains and pH studies. CONCLUSIONS: The lipid index is an effective, non-invasive screening test that provides direct evidence of esophageal aspiration. Patients with high positive results should proceed to surgical assessment for Nissen fundoplication. J Heart Lung Transplant 2010;29:859-64 Crown Copyright (C) 2010 Published by Elsevier Inc. All rights reserved.