24 - Accuracy of Synovial Fluid Biomarkers for Culture-Positive Septic Arthritis in a Lyme Endemic Region

Friday, April 28, 2023

5:15 PM – 7:15 PM ET

Poster Number: 24
Publication Number: 24.11

Andzelika Dechnik, Boston Children's Hospital and Boston Medical Center, Brookline, MA, United States; Caroline G. Kahane, Boston Children's Hospital, Boston, MA, United States; Lise E. Nigrovic, Boston Children's Hospital, Boston, MA, United States; Todd W. Lyons, Boston Children's Hospital, Wayland, MA, United States

Presenting Author(s)

Todd W. Lyons, MD, MPH

Assistant Professor
Boston Children's Hospital
Wayland, Massachusetts, United States

Co-Author(s)

Andzelika Dechnik, MD

Pediatric Resident Physician
Boston Children's Hospital and Boston Medical Center
Brookline, Massachusetts, United States

Background: Septic arthritis is challenging to diagnose as symptoms and laboratory results overlap with other types of arthritis, including Lyme arthritis. Arthrocentesis may be performed in cases of diagnostic uncertainty with synovial fluid biomarkers used to guide initial clinical decision-making although cultures take several days to result.

Objective: To evaluate the ability of synovial fluid biomarkers to discriminate between children with septic vs. other types of arthritis.

Design/Methods: We performed a retrospective cohort study of children aged 6 months to 18 years who presented to a single emergency department located in a Lyme disease endemic area between 2007 and 2022 who had a diagnostic arthrocentesis performed. Our primary outcome was septic arthritis, defined as a positive synovial fluid culture for a pathogenic bacteria. We compared the ability of commonly obtained synovial fluid biomarkers to discriminate between children with septic and other types of arthritis using the area under the receiver operator curve for the following: white blood cell (WBC) count, % neutrophils, absolute neutrophil count (ANC), glucose and protein.

Results: Of the 788 children undergoing diagnostic arthrocentesis, 79 (10%) had septic arthritis and 206 (26%) had Lyme arthritis. The median patient age was 8 years (interquartile range 5-12 years) and 484 (61%) were male. Compared to synovial fluid WBC count [AUC 0.72 (95%CI 0.65-0.78)], ANC [AUC 0.72 (95%CI 0.66-0.79), p=0.09], % neutrophils [AUC 0.66 (95%CI 0.60-0.71), p=0.12], and glucose [AUC 0.78 (95%CI 0.67-0.90), p=0.33] performed similarly, but protein [AUC 0.52 (95% CI 0.40-0.63), p=0.04] had lower accuracy for septic arthritis (Figure 1). Importantly, 49 (62% of the children with septic arthritis) had a synovial fluid WBC > 50,000 cells/mm³. The test performance of commonly used synovial fluid biomarker thresholds are reported in Table 1.

Conclusion(s): For children undergoing diagnostic arthrocentesis, children with septic and other types of arthritis had overlapping synovial fluid biomarkers. Additional tools are needed to accurate identify children at low and high risk for septic arthritis prior to availability of synovial fluid culture results.