Neutrophil Percentages in Bronchoalveolar Lavage Fluid: Implications for Diagnosing Bacterial Pneumonia in Patients with Immunocompromise and Neutropenia

Overview

Journal medRxiv

Date 2024 May 20

PMID 38766045

Authors

Kevin M Grudzinski

Samuel Fenske

Alec Peltekian

Nikolay S Markov

Anna Pawlowski

Mengjia Kang

James M Walter

Chiagozie I Pickens

Nandita R Nadig

Ankit Agrawal

Benjamin D Singer

Richard G Wunderink

Catherine A Gao

Affiliations

Soon will be listed here.

Abstract

Rationale: Pneumonia is the most common infection in ICU patients and a leading cause for death. Assessment of bronchoalveolar lavage fluid (BALF) cellularity can aid in pneumonia diagnosis. Low percentages (<50%) of BALF neutrophils have a high negative predictive value for bacterial pneumonia in a general medical ICU population. The operating characteristics in patients with immunocompromise and neutropenia are less clear.

Objective: To compare BALF % neutrophils operating characteristics in patients with and without immunocompromise or neutropenia.

Methods: This was a single center observational cohort study. Patients were categorized into three groups: (1) patients with neutropenia, (2) patients with underlying immunocompromise, and (3) patients with neither. BAL-level analysis reflected neutropenia and immunocompromise state on day of BAL sampling. Operating characteristics of BALF % neutrophils were calculated using varying thresholds of alveolar neutrophilia. Median [Q1,Q3] are reported for nonparametric data and compared using Mann-Whitney U tests.

Results: 688 mechanically ventilated patients had 1736 BAL samples. Among bacterial pneumonia episodes, no difference was found in BALF % neutrophils between patients with underlying immunocompromise and patients with neither neutropenia nor immunocompromise on day of sampling: 82.0% [61.0, 91.0] vs 81.0% [66.0, 91.0], p=0.859. However, when neutropenic on day of sampling, the median BALF % neutrophils was 35.0% [8.8, 67.5] (p<0.001 compared with other categories). In patients with neutropenia, a BALF % neutrophil threshold of 7% had a sensitivity of 90% for excluding bacterial pneumonia.

Conclusions: We found that among patients with bacterial pneumonia, BALF % neutrophil was not significantly lower in patients with a broad spectrum of immunocompromised states but was significantly lower when measured during acute neutropenia. We found varying thresholds of BALF % neutrophils across the three groups. Patients with neutropenia who mount even a low percent of alveolar neutrophils should raise concern for bacterial pneumonia.

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