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

Abstract

Background: Gastroesophageal reflux disease (GORD) and microaspiration may be associated with acute graft dysfunction and development of obliterative bronchiolitis (OB) after lung transplantation. The "gold standard" for diagnosis of GORD is the 24-hour esophageal pH-monitoring study, although no simple, non-invasive screening test is routinely employed. Oil red O staining of alveolar macrophages in bronchoalveolar 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.