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Topic:

Septic Arthritis

Issue:

Hip

Category:

Congenital

Title:

Aspirations Dashed: Conventional Synovial Fluid Analysis Is Superior to Synovial Fluid and Blood Neutrophil-to-Lymphocyte Ratios in Diagnosing Pediatric Septic Arthritis of the Hip and Knee

Author:

DeFrancesco, Christopher J. MD; VanEenenaam, David P. Jr BS; Hall, Carter E. BS; Desai, Vineet M. BS; Orellana, Kevin BS; Sankar, Wudbhav N. MD

Journal:

Journal of Pediatric Orthopaedics

Date:

November/December 2024

Reference:

44(10): p e938-e944, DOI: 10.1097/BPO.0000000000002785

Level Of Evidence:

III

# of Patients:

394

Study Type:

Retrospective cohort study

Location:

Large urban tertiary-care children’s hospital

Summary:

The study examines whether synovial fluid neutrophil-to-lymphocyte ratio (SF-NLR) and blood neutrophil-to-lymphocyte ratio (B-NLR) are reliable diagnostic tools for septic arthritis (SA) in children, comparing these ratios to the conventional synovial fluid analysis (CCT) method. It finds that SF-NLR and B-NLR are not strong diagnostic indicators in pediatric SA cases.

Methods:

Retrospective analysis of emergency department visits between 2012 and 2023, where synovial fluid analysis was performed to diagnose SA of the hip or knee. Patients over 18 were excluded. The CCT was compared to SF-NLR and B-NLR in diagnosing culture-positive septic arthritis (CPSA). Receiver operating characteristic (ROC) curves were used to evaluate diagnostic accuracy.

Exclusions:

Patients aged 18 years or older

Results:

The study found that SF-NLR and B-NLR did not significantly differ between CPSA and culture-negative (CN) patients (P=0.93 and P=0.37, respectively). The CCT showed 91% sensitivity but only 35% specificity. SF-WBC was superior to SF-NLR and B-NLR in diagnosing CPSA (AUC=0.71 vs. 0.50 and 0.53, respectively; both P<0.01). Additionally, 48.8% of CCT-positive, culture-negative patients tested positive for Lyme disease.

Conclusions:

SF-NLR and B-NLR are not reliable diagnostic tools for pediatric SA of the hip or knee, unlike in adults. The findings highlight the importance of conventional synovial fluid analysis (SF-WBC) and suggest that Lyme disease may be a factor in culture-negative cases. Further studies outside Lyme-endemic areas are recommended.

Relevance:

Limitations:

Perspective:

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