Lipid-laden macrophage index as a marker of aspiration in children, is it reliable? A scoping review

Abstract

Introduction: A diagnostic pathway to detect aspiration is challenging and usually requires a multidisciplinary approach and a variety of tests. Lipid-laden macrophage index (LLMI) was first described in 1985 by Corwin and Irwin as a promising tool to detect aspiration. Information in the literature as well as physicians' opinions about the clinical value of the LLMI remains controversial.

Objectives: To assess the clinical value and possible limitations of LLMI as a diagnostic marker for detecting aspiration in children.

Methods: Based on the available literature we thought to answer the following questions: 1. Is there a reliable cutoff value of LLMI to detect aspiration? 2. What are the limitations of LLMI? We queried 8 electronic databases: Medline, Embase, CINAHL, Cochrane, Global Health, Web of Science, Africa Wide Information, and Global Index Medicus. Studies were selected based on established study criteria. Search was limited to publications in English language including human and animal studies. Authors reviewed 2900 articles and identified 21 relevant to the studied subject.

Results: Research reveals different proposed cutoff values for aspirators ranging from 85 to 200 macrophages. LLMI reliability has several limitations including: inter- and intraobserver variability among pathologists scores, inability to differentiate between exogenous and endogenous lipid content, inconsistencies in the definition of the term "aspiration" in various publications. Also, studies in animal models have shown that the nature of the disease, frequency of aspiration, and the time frame when bronchoalveolar lavage (BAL) is performed, could all contribute to the overlap in LLMI in aspirators versus non-aspirators.

Discussion: Our research demonstrates the limitations of LLMI in distinguishing between aspirators and non-aspirators. We believe based on these findings that airway teams should audit their local data as to the value of BAL in detecting aspiration in their patient population.

Keywords: Alveolar macrophages; Aspiration; Children; Lipid-laden macrophages index; Pulmonary pathology.