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Synovial Fluid Absolute Neutrophil Count and Neutrophil-To-Lymphocyte Ratio are not Superior to Polymorphonuclear
Julian E Dilley1, Abhijit Seetharam1, R Michael Meneghini1
1Department of Orthopaedic Surgery, Indiana University School of Medicine, Indianapolis, Indiana.
Background:
Serum and synovial biomarkers are currently used to diagnose periprosthetic joint infection (PJI). Serum neutrophil-to-lymphocyte ratio (NLR) has shown promise as an inexpensive test in diagnosing infection, but there are no reports of synovial NLR or absolute neutrophil count (ANC) for diagnosing chronic PJI. The purpose of this study was to investigate the diagnostic potential of both markers.
Methods:
A retrospective review of 730 patients who underwent total joint arthroplasty and subsequent aspiration was conducted. Synovial white blood cell (WBC) count, synovial polymorphonuclear percentage (PMN%), synovial NLR, synovial ANC, serum erythrocyte sedimentation rate (ESR), serum C-reactive protein (CRP), serum WBC, serum PMN%, serum NLR, and serum ANC had their utility in diagnosing PJI examined by area-under-the-curve analyses (AUC). Pairwise comparisons of AUCs were performed.
Results:
The AUCs for synovial WBC, PMN%, NLR, and ANC were 0.84, 0.84, 0.83, and 0.85, respectively. Synovial fluid ANC was a superior marker to synovial NLR (P = .027) and synovial WBC (P = .003) but not PMN% (P = .365). Synovial NLR was inferior to PMN% (P = .006) but not different from synovial WBC (P > .05). The AUCs for serum ESR, CRP, WBC, PMN%, NLR, and ANC were 0.70, 0.79, 0.63, 0.72, 0.74, and 0.67, respectively. Serum CRP outperformed all other serum markers (P < .05) except for PMN% and NLR (P > .05). Serum PMN% and NLR were similar to serum ESR (P > .05).
Conclusion:
Synovial ANC had similar performance to PMN% in diagnosing chronic PJI, whereas synovial NLR was a worse diagnostic marker. The lack of superiority to synovial PMN% limits the utility of these tests compared to established criteria.
Insights
Synovial fluid absolute neutrophil count (ANC) shows promise for diagnosing periprosthetic joint infection (PJI), performing similarly to polymorphonuclear percentage (PMN%). Synovial neutrophil-to-lymphocyte ratio (NLR) is less effective for diagnosing chronic PJI.
Area of Science:
- Orthopedic Surgery
- Infectious Disease
- Biomarker Discovery
Background:
- Periprosthetic joint infection (PJI) diagnosis relies on serum and synovial biomarkers.
- Serum neutrophil-to-lymphocyte ratio (NLR) is a cost-effective infection marker.
- Synovial NLR and absolute neutrophil count (ANC) have not been evaluated for chronic PJI diagnosis.
Purpose of the Study:
- To investigate the diagnostic potential of synovial NLR and ANC for chronic PJI.
- To compare these novel markers against established synovial and serum biomarkers.
Main Methods:
- Retrospective review of 730 patients with total joint arthroplasty and aspiration.
- Analysis of synovial and serum biomarkers including white blood cell (WBC) count, polymorphonuclear percentage (PMN%), NLR, and ANC.
- Area-under-the-curve (AUC) analyses and pairwise comparisons to assess diagnostic utility.
Main Results:
- Synovial ANC (AUC=0.85) and PMN% (AUC=0.84) demonstrated high diagnostic performance for PJI.
- Synovial ANC was superior to synovial NLR (AUC=0.83) and synovial WBC (AUC=0.84).
- Serum C-reactive protein (CRP) was the best serum marker, outperforming others except PMN% and NLR.
Conclusions:
- Synovial ANC is a valuable diagnostic marker for chronic PJI, comparable to synovial PMN%.
- Synovial NLR showed inferior diagnostic performance compared to synovial PMN%.
- The diagnostic utility of these novel synovial markers is limited compared to existing criteria.
