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

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.

Lipid‐Laden Macrophage Index as a Diagnostic Tool for Pediatric Aspiration: A Systematic Review

Objective

Lipid-laden macrophage index (LLMI) has been proposed as a marker for aspiration on bronchoalveolar lavage. It has also been studied as a marker for gastroesophageal reflux and other pulmonary diseases. This review aims to determine the clinical correlation between LLMI and pediatric aspiration.

Data Sources

PubMed (MeSH search), Scopus, and Cochrane Central Register of Controlled Trials (CENTRAL) portals through December 17th, 2020.

Review Methods

Preferred Reporting Items for Systematic Review and Meta-Analysis criteria were followed, and a quality assessment of included studies was performed using the Methodological Index for Non-Randomized Studies. Search criteria included all occurrences in the title or abstract of the terms "pulmonary aspiration" and "alveolar macrophages."

Results

Five studies describing 720 patients met inclusion, 3 retrospective case-control studies, and 2 prospective observational studies. Four studies suggested a link between elevated LLMI and aspiration, and 1 found no association. Control groups varied and included healthy nonaspirators to nonaspirators with other pulmonary diseases. Diagnosis of aspiration was not standardized across the studies. Three papers proposed cutoff values for LLMI, all different.

Conclusion

The existing literature indicates that LLMI is not a sensitive or specific marker for aspiration. Further study is needed to define the utility of LLMI in pediatric aspiration.

Utilization of Oil Red O staining for assessing aspiration risk in lung transplant patients: A multidisciplinary prospective study with clinical practice insights

BACKGROUND

Gastroesophageal reflux disease with microaspiration has been associated with graft dysfunction in lung transplant patients. Identifying patients with aspiration is clinically important because it enables implementation of appropriate interventions like antireflux therapy. Oil Red O (ORO) staining with determination of the lipid-laden macrophage index (LLMI) has been proposed as a noninvasive surrogate marker in the detection of aspiration. The aim of this study was to prospectively evaluate clinical utilization of ORO staining in the assessment of aspiration risk.

METHODS

All transbronchial surgical pathology biopsies obtained in lung transplant patients undergoing routine surveillance from August 2020 through November 2021 were included in this study. Clinical team members prospectively ascertained the aspiration risk category (ARC) of each patient both before and after biopsy findings and recorded reasons for change in ARC.

RESULTS

A total of 132 transbronchial biopsies with concurrent LLMI were included in the study. LLMI was low in 51 cases (38.6%), including 21 of the 54 cases (38.9%) where aspiration was suggested based on the transbronchial biopsy findings. In total, 19 cases (14.4%) underwent a change in ARC post-biopsy including 10 that were upgraded and nine cases that were downgraded. Transbronchial biopsy findings were noted as the reason for change in ARC in the majority (15/19; 79%) of cases; only a minority (2/19; 10.5%) were due to the LLMI. Notably, 16 cases (12.1%) had a low LLMI with high-risk post-biopsy ARC and nine cases (6.8%) had a high LLMI with low-risk post-biopsy ARC.

CONCLUSIONS

This study observed that clinical evaluation for aspiration relied more heavily on transbronchial biopsy findings. Although LLMI may retain clinical utility in some scenarios, reevaluation of the clinical value of ORO testing would be prudent.

Correlation between cytology Oil Red O staining and lung biopsy specimens: utility of the lipid-laden macrophage index

INTRODUCTION

Oil Red O staining is used for enumeration of the lipid-laden macrophage index (LLMI) as a surrogate for aspiration. As part of quality improvement efforts aimed at optimizing resource utilization, the utility of this stain in current cytopathology practice was re-evaluated. The objective of this study was to explore the clinical utility of Oil Red O staining in bronchoalveolar lavage (BAL) samples by correlating the LLMI with findings in concurrent histologic tissue samples.

MATERIALS AND METHODS

Lung transbronchial biopsy specimens that suggested aspiration that were submitted with concurrent BAL cytology samples were retrieved. Lung tissue biopsies were reviewed for the presence of foamy alveolar macrophages (graded as 0, 1+, and 2+), foreign material, and giant cells. The concurrent BAL was reviewed with consensus determination of the LLMI.

RESULTS

A total of 53 cases were identified. On histology, 13 cases (24.5%) were found to have no foamy alveolar macrophages, 23 cases (43.4%) were found to have 1+ foamy alveolar macrophages, and 17 cases (32.1%) were found to have 2+ foamy alveolar macrophages. Six cases (11.3%) were found to have foreign material, and 10 cases (18.9%) were found to have multinucleated giant cells. The average LLMI score was 16, with 44 (83.0%) in the low range (LLMI <40) and 9 (17.0%) in the intermediate range (LLMI of 40-90).

CONCLUSIONS

None of the cases in our study had an LLMI that exceeded the cutoff value for which aspiration would be suspected. We found no correlation of the LLMI with lung biopsies that suggested aspiration.

Bronchoalveolar Lavage in a Pediatric Population

OBJECTIVES

The cytomorphologic findings of bronchoalveolar lavage (BAL) in pediatrics were correlated with clinical symptoms.

METHODS

Patient demographics, clinical symptoms/history, cytomorphologic findings, and oil red O (ORO) staining of 100 pediatric patients who underwent BAL between 2014 and 2016 were reviewed at a large academic institution.

RESULTS

Of the 100 patients (males/females, 62:38), the most common conditions for BAL included cough (46/100), reflux (39/100), pneumonia (30/100), dysphagia (22/100), asthma (19/100), and cystic fibrosis (15/100). Sixteen of 100 patients were admitted with pulmonary symptoms from the emergency department. Cytomorphologic findings showed acute inflammation in 37 BALs and chronic inflammation in 9. Abundant thick mucin was present in 3 cytology cases from patients with cystic fibrosis. Fungal elements were detected in 3 cases (Candida, Aspergillus, and Pneumocystis jirovecii) and viral effects (rhinovirus) in one. Thirty-seven of 100 had rare ORO-positive lipid-laden macrophages (LLMs), 7 of 100 had moderate LLMs, 11 of 100 had numerous LLMs, 18 of 100 had positive staining without the degree of staining, 25 of 100 had negative ORO staining, and 2 of 100 had noncontributory ORO staining. An iron stain was done on 15 BALs (2 positive, 9 negative, and 4 noncontributory).

CONCLUSIONS

BAL cytology is a useful tool in pediatrics to discriminate underlying causes of aerodigestive system conditions, while ORO staining may occasionally help.

Oil red O staining for lipid-laden macrophage index of bronchoalveolar lavage: interobserver agreement and challenges to interpretation

INTRODUCTION

Oil Red O (ORO) staining on cytologic specimens with calculation of the lipid-laden macrophage index (LLMI) is used as a part of the workup in a number of clinical settings, particularly when aspiration is of concern. As a part of ongoing internal quality improvement measures, the objective of the present study was to evaluate the interobserver agreement of the LLMI calculation and to identify factors that affect the variability of the calculation.

MATERIALS AND METHODS

There were 9 study participants, which included 3 trainees, 3 cytotechnologists, and 3 cytopathologists. Each participant reviewed 100 ORO-stained bronchoalveolar lavage slides and assigned an LLMI score to each case. The scores were categorized into 3 groups according to the associated aspiration risk: low, LLMI <40; intermediate, LLMI 40 to 90; and high, LLMI >90. The participants were also requested to note any challenges to the calculation for each case.

RESULTS

The interobserver agreement among all participants was fair (κ = 0.23). Stratified by participant group, the interobserver agreement among the trainees was fair (κ = 0.24), among cytotechnologists was fair (κ = 0.32), and among cytopathologists was moderate (κ = 0.60). In 70 cases, at least one participant scored the case at least one category higher than the other participants; in 47 cases there was a two category difference. A primary diagnostic challenge reported by participants was macrophage pigmentation (hemosiderin, anthracosis).

CONCLUSIONS

We found only fair interobserver agreement among all 9 participants in the study. Hemosiderin and anthracotic pigmentation was a major factor impeding LLMI calculation resulting in overestimation of the LLMI.

Testing for lipid-laden macrophages in bronchoalveolar lavage fluid to diagnose vaping-associated pulmonary injury. Are we there yet?

Vaping-associated pulmonary injury (VAPI) is a severe respiratory disorder associated with the inhalation of nicotine, tetrahydrocannabinol, cannabidiol, or other active substances through a personal vaporizer ("vaping"). Within 2 months after its description, the disease has reached epidemic proportion, affecting over 2000 people and resulting in a number of fatalities. The substance(s) responsible for the lung injury are still unknown, and the pathophysiology of the disease is still incompletely understood. The manifestations of the disease are protean, and the insidiously starting respiratory, gastrointestinal, and constitutional symptoms may initially resemble a viral flu-like illness. The disease may increase in severity, requiring hospitalization, and in more severe cases, mechanical ventilation. The diagnosis of VAPI currently relies on the identification of pulmonary infiltrates on imaging studies in patients who have used vaping products, after excluding infections and other plausible alternative diagnoses. Because VAPI is currently a diagnosis of exclusion, some authors have suggested the use of lipid-laden macrophages (LLM) as a diagnostic test to confirm the disease. We review the current state of the knowledge about the pathologic basis of VAPI, and the literature on the analytic performance of the LLM test to better understand the potential utility of this test in the diagnosis of VAPI. Our review finds little evidence to suggest the use of LLM in the diagnosis of VAPI, since its underlying pathology is acute lung injury, which is unrelated to LLM, and the frequency of their detection varies greatly in different reported series.

Mixed Lipid, Fish Oil, and Soybean Oil Parenteral Lipids Impact Cholestasis, Hepatic Phytosterol, and Lipid Composition

OBJECTIVES

In parenteral nutrition-dependent infants and children, intestinal failure (IF)-associated liver disease (IFALD) remains an important problem. A comparative study was undertaken of parenteral mixed lipid (ML), ω-3 predominant fish oil (FO), and ω-6 predominant soybean oil (SO) emulsions in regards to hepatic phytosterol, neutral lipid, fatty acid (FA) content, and the relationship to cholestasis in piglets.

METHODS

Neonatal piglets received parenteral nutrition, varying in lipid dose (5 or 10 g· kg · day) and formulation: SO5 (n = 5), SO10 (n = 5), FO5 (n = 5), and ML10 (n = 5). On day 14, liver chemistry, bile flow, histology and neutral lipid staining were assessed. Hepatic triglyceride FA content was determined using thin layer and gas chromatography, and phytosterol content was assessed using gas chromatography-mass spectrometry.

RESULTS

SO groups had higher prevalence of biochemical cholestasis (P < 0.04) and lower bile flow (P < 0.0001). Hepatic campesterol, stigmasterol, and β-sitosterol were highest in SO10 (P < 0.0001). Hepatic FA (P < 0.03) and ω-6/ω-3 FA ratio (P < 0.0001) were higher in the SO groups. Neutral lipid accumulation (P = 0.3) and liver histology (P = 0.16) were not different between groups. Univariate predictors of bile flow were: campesterol (r = -0.77, P = 0.001), β-sitosterol (r = -0.74, P = 0.002), stigmasterol (r = -0.74, P = 0.002), ω-6 FA (r = -0.72, P = 0.002), and ω-3 FA (r = 0.59, P = 0.02). Only campesterol independently predicted bile flow.

CONCLUSIONS

ML and FO lipid emulsions reduce cholestasis in association with lowered hepatic phytosterol and lipid content. Lower hepatic phytosterol and ω-6 FA content, and higher ω-3 FA content are hepatoprotective. Multivariate analysis suggests reduced phytosterol accumulation may best explain the hepatoprotective effect of fish oil-containing lipids.

Prevalence of pediatric aspiration-associated extraesophageal reflux disease

IMPORTANCE

The role of aspiration-associated extraesophageal reflux disease (AERD) in patients with chronic respiratory symptoms is not well defined. Identifying the frequency of AERD in these patients may provide guidance in their treatment.

OBJECTIVE

To determine the prevalence of AERD in patients with chronic respiratory symptoms and to assess the utility of pepsin as a new marker for AERD.

DESIGN

Case-control study performed from 2008 through 2012.Western blot analysis for pepsin and oil red O staining for lipid-laden macrophages (LLMs) was performed on bronchoalveolar lavage fluid specimens.

SETTING

Tertiary referral center.

PARTICIPANTS

Sixty-five patients (aged 4.5 months to 24 years) with chronic pulmonary disease, with or without tracheostomy, were compared with controls undergoing elective surgery who had no history of pulmonary disease.

MAIN OUTCOMES AND MEASURES

Presence of pepsin and LLMs and quantity of LLMs in specimens.

RESULTS

Seventy-six total patients participated: 34 patients who underwent bronchoscopy, 31 patients with tracheostomy, and 11 controls. Pepsin-positive bronchoalveolar lavage fluid specimens were identified in 25 patients who underwent bronchoscopy (74%) and 22 patients with tracheostomy (71%). All specimens from controls were negative for pepsin. Presence of LLMs was identified in specimens from 31 patients in the bronchoscopy group (91%), 16 patients in the tracheostomy group (52%), and 7 controls (64%), with a similar distribution of the quantity of LLMs in each lavage fluid specimen among the groups.

CONCLUSIONS AND RELEVANCE

Patients with chronic pulmonary disease have a high prevalence of AERD, which may have important treatment implications. The presence of pepsin was a better predictor of AERD in patients with respiratory symptoms compared with controls than presence of LLMs. Detection of pepsin in bronchoalveolar lavage fluid specimens can serve as a biomarker for AERD and is potentially superior to the current method of measuring LLMs. Whereas there is a significant association between AERD and the presence of chronic respiratory symptoms, this study does not verify causation. Additional study investigating the mechanism of pepsin on the respiratory epithelium may further our understanding of the pathophysiologic characteristics of this association and provide additional management options for these patients.

Reflux aspiration in children with neurodisability--a significant problem, but can we measure it?

Recurrent respiratory problems are common in children with severe neurodisability, and respiratory deterioration is a leading cause of premature death in this group. Although the etiology is multifactorial, recurrent pulmonary aspiration is thought to play a significant role. Gastroesophageal reflux is known to be common, as is oral-motor discoordination. Differentiating direct aspiration of food and saliva and gastric reflux aspiration is difficult and presents a challenge in managing patients and assessing their suitability for surgical antireflux procedures. This is particularly the case when children present with predominantly respiratory symptoms, where there may be direct aspiration, reflux aspiration, neither, or both. A clinical biomarker to identify and quantify reflux aspiration would therefore be useful in surgical assessment and may also be applicable as an outcome measure for clinical trials of antireflux surgery. In this review, we discuss the evidence base behind existing and potentially novel biomarkers of aspiration in bronchoalveolar lavage fluid. We highlight the limitations of the lipid-laden macrophage index, particularly with regard to its specificity and interrater/intrarater reliability. We discuss the laboratory methods available to measure promising new biomarkers (pepsin and bile acids) and highlight their potential advantages and disadvantages. Finally, to understand how aspiration causes clinical signs and symptoms in our patients, we need to study the effect of aspirated substances on the lung, and here we review the available in vivo and in vitro literature.

Utilization of lipid-laden macrophage index in evaluation of aerodigestive disorders

OBJECTIVES/HYPOTHESIS

The utility of the lipid-laden macrophage index (LLMI) in the evaluation of airway inflammatory processes remains controversial. There is a paucity of normative data in both pediatric and adult populations, and there is wide variability in the reported cases. The goal of this project was to review the LLMI levels in a large series of patients with a wide range of well-documented pulmonary and airway diseases (cystic fibrosis, aspiration, tracheo/bronchomalacia, recurrent pneumonia, asthma, immunosuppressed conditions, and laryngeal clefts) to develop a better understanding of the clinical utility of the LLMI.

STUDY DESIGN

This study is a retrospective analysis of patients who underwent initial bronchoscopy with broncheoalveolar lavage (BAL) and had specimens sent for determination of LLMI. This study was performed at a major pediatric tertiary care medical center from April 12, 2006 to July 13, 2009.

METHODS

Medical charts were reviewed for major diagnoses, indications for bronchoscopy, the side of lung (right versus left), documented aspiration, suspected aspiration, neutrophil counts, and patient age. These qualitative and quantitative variables were considered in relation to the LLMI.

RESULTS

The cohort of patients examined were 4.9 ± 4.3 years (4 days to 18 years of age). Forty-two percent were female and 58% were male. The highest median LLMI was in immunocompromised patients with a median of 78. Recurrent pneumonia, aspiration, tracheo/bronchomalacia, and cystic fibrosis had median LLMI levels of 55, 49, 40, and 50, respectively. There was a wide range of LLMI within each primary diagnosis. There was no significant correlation between neutrophils percentage in the BAL and LLMI. There were no significant differences between BAL specimens obtained from the right or left side.

CONCLUSIONS

To our knowledge, this is the largest series of patients reported in the literature to have an LLMI compared with underlying diagnoses. Based on our data and analyses, there is wide variability between the range of LLMI and the primary diagnosis. As such, the diagnostic utility of the LLMI is limited and should be interpreted with caution.