Septic Arthritis in Immunosuppressed Patients: Do Laboratory Values Help?

Area of Science:

• Rheumatology
• Infectious Diseases
• Orthopedic Surgery

Background:

• Septic arthritis diagnosis often relies on synovial fluid cell count thresholds.
• A commonly cited threshold is 50,000 cells/mm^-3.
• The efficacy of this threshold in immunosuppressed patients remains unclear.

Purpose of the Study:

• To evaluate the diagnostic utility of synovial fluid cell count thresholds for septic arthritis in immunosuppressed patients.
• To determine if traditional diagnostic criteria are applicable to this patient population.

Main Methods:

• Retrospective review of 33 immunosuppressed patients diagnosed with septic arthritis between 2008 and 2018.
• Comparison of culture-positive septic arthritis cases with culture-negative cases.
• Analysis of synovial fluid cell counts, neutrophil percentages, ESR, and CRP levels.

Main Results:

• No statistically significant differences were observed in synovial fluid cell count, neutrophil percentage, ESR, or CRP between culture-positive and culture-negative groups (P=0.081).
• The median synovial fluid cell count in culture-positive patients was 29,000 cells/mm^-3.
• Only 31.2% of culture-positive patients exceeded the 50,000 cells/mm^-3 threshold.

Conclusions:

• Traditional synovial fluid cell count thresholds are not a reliable diagnostic tool for septic arthritis in immunosuppressed individuals.
• Alternative or adjunctive diagnostic methods may be necessary for this patient group.