# Biomarkers for pneumonia after major trauma: A systematic review and meta-analysis

## TL;DR

This study reviews blood-based biomarkers for predicting pneumonia in major trauma patients, identifying several candidates but highlighting the need for more consistent research.

## Contribution

The paper systematically evaluates and meta-analyzes blood-based biomarkers for pneumonia in major trauma patients, identifying specific candidates with statistical significance.

## Key findings

- Interleukin-6 (IL-6), CYFRA21-1, and leucocyte count were higher in pneumonia patients at admission.
- IL-10 and neutrophil oxidative burst capacity were significantly elevated in pneumonia patients during hospitalization.
- CRP levels were higher in pneumonia patients on multiple days during hospitalization.

## Abstract

Major trauma is a significant global health issue. Pneumonia poses an additional risk for morbidity and mortality after major trauma yet identifying pneumonia remains challenging in clinical practice. This systematic review aims to evaluate blood-based biomarkers for pneumonia in major trauma patients.

The search was performed across four databases up to November 18th 2024, including primary studies investigating blood-based biomarkers associated with pneumonia in adults hospitalised after major trauma (PROSPERO CRD42024542059). Risk of bias was assessed using the ROBINS-E tool and meta-analysis was performed of pooled data.

Among 20 included studies, with a total of 4316 participants, the pooled mean pneumonia rate was 32.7% (23.5%–43.4%). Seventy biomarkers for post-operative pneumonia were identified, with meta-analysis possible for 12 of the reported biomarkers. At admission interleukin (IL)-6 (standardised mean difference: 1.41 (0.04–2.77), p = 0.04), cytokeratin fragment 21-1 (CYFRA21-1; 0.53 (0.19–0.86), p = 0.002) and leucocyte count (0.28 (0.05–0.50), p = 0.01) were higher in patients who developed pneumonia. During hospitalisation, patients with pneumonia had significantly higher IL-10 (4.42 (3.89–4.95), p > 0.001) and neutrophil oxidative burst capacity (1.52 (0.96–2.09), p > 0.001) at day 1, CYFRA21-1 at day 2 (0.43 (0.10–0.76), p = 0.01), IL-6 at day 3 (3.11 (2.66–3.55), p > 0.001) and day 5 (0.57 (0.05–1.09), p = 0.03) and CRP at day 4 (1.87 (1.51–2.24), p > 0.001), day 5 (1.38 (1.03–1.72), p > 0.001), day 6 (0.74 (0.42–1.06), p > 0.001) and day 7 (0.87 (0.12–1.63), p = 0.02). Across the included studies, 85% exhibited some concerns to very high risk of bias.

While we identified potential candidate biomarkers for pneumonia in major trauma patients, the high heterogeneity across trauma populations, clinical diagnostic tools and biomarker testing methods warrants further high-quality studies to confirm their clinical value.