# Synovial Periprosthetic Infection Markers Show High Variability in Different Clinical and Microbiological Settings

## TL;DR

This study shows that synovial markers like WBC and PMN vary greatly depending on infection type and clinical factors in joint infections.

## Contribution

The study reveals how synovial markers are influenced by infection virulence, symptom duration, and histology in periprosthetic joint infections.

## Key findings

- WBC and PMN levels were higher in patients with successful pathogen detection.
- High-virulent infections showed significantly higher WBC compared to low-virulent ones.
- Symptoms lasting ≤4 weeks correlated with higher WBC and PMN levels.

## Abstract

Background/Objectives: Accurately diagnosing a periprosthetic joint infection (PJI) represents a challenging and complex task. Especially in the case of low-grade infections, important diagnostic modalities may be inconclusive and synovial markers such as white blood cell count (WBC) and polymorphonuclear percentage (PMN) gain relevance. We therefore aim to assess WBC and PMN in different clinical and microbiological settings. Methods: We performed a retrospective analysis of 115 patients with a diagnosed PJI. WBC and PMN were compared between patients with low- and high-virulent infections, negative and positive histology, symptom duration ≤ 4 weeks and >4 weeks, and positive and negative pathogen detection. Results: Synovial WBC was significantly higher in patients with successful pathogen detection (42.44 [87.0] G/L vs. 16.35 [32.0] G/L; p < 0.01), as was PMN (86.0 [60.0]% vs. 91.0 [89.0]%; p < 0.01). PJIs with high-virulent pathogens showed higher WBC compared to low-virulent pathogens (58.27 [102.0] G/L vs. 27.27 [46.0] G/L; p < 0.01). Patients with onset of symptoms ≤ 4 weeks demonstrated higher WBC (58.27 [112.0] G/L vs. 16.42 [46.0] G/L]; p < 0.01) as well as higher PMN (91.5 [9.0]% vs. 88.0 [20.0]%); p = 0.042). Cases with negative histology showed significantly lower WBC (16.73 [44.0] G/L vs. 42.86 [87.0] G/L; p < 0.01) and lower PMN (86.0 [67.0]% vs. 91.0 [9.0]%; p = 0.036). Conclusions: WBC and PMN show high variability and appear to be influenced by virulence, histology, onset of symptoms, and pathogen detection.