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How Reliable Is the Absolute Synovial Polymorphonuclear Neutrophil Cell Count in Diagnosing Periprosthetic Joint
Taner Karlidag1, T David Luo2, Thorsten Gehrke1
1Department of Orthopaedic Surgery, Helios ENDO-Klinik Hamburg, Hamburg, Germany.
Background:
Diagnosing periprosthetic joint infection (PJI) is a daunting task for even the most experienced orthopedic surgeons, as there is currently no test available that can provide absolute accuracy. Utilizing an established synovial indicator for detecting PJI without incurring additional costs or resources would be the optimal solution for predicting the presence of infection. Therefore, we hypothesized that synovial absolute neutrophil count (ANC) would improve the diagnostic accuracy of chronic knee and hip PJI.
Methods:
The study included 260 patients (134 men and 126 women, mean age of 70 years [range, 26 to 89]) who underwent aspiration during preoperative workup. Of these, 109 patients (41.9%) were diagnosed with chronic PJI (50 knees, 59 hips), and 151 patients (58.1%) were diagnosed as aseptic (94 knees, 57 hips). Data obtained from all patients included age, sex, procedure type (total hip or total knee arthroplasty), operation side, synovial white blood cell count (cells/μL), synovial polymorphonuclear cells percentage, and synovial α-defensin immunoassay value at the admission were retrieved from the electronic medical record.
Results:
The calculated optimal threshold for synovial ANC of 1,415.5 cells/μL was associated with an area under the receiver operating characteristic curve (AUC) of 0.930 for chronic knee PJI diagnosis. The calculated optimal threshold for synovial ANC of 2,247 cells/μL was associated with an AUC of 0.905 for chronic hip PJI diagnosis.
Conclusions:
This study has conclusively shown that the synovial ANC serves as a valuable marker in the complicated diagnosis of PJI. This highly effective and efficient approach should be utilized for obtaining further information through standard tests, thereby ruling out the possibility of PJI.
Level Of Evidence:
III.
Insights
Synovial absolute neutrophil count (ANC) significantly improves diagnosing periprosthetic joint infection (PJI). This cost-effective method aids orthopedic surgeons in accurately identifying knee and hip PJI, reducing diagnostic uncertainty.
Area of Science:
- Orthopedics
- Infectious Diseases
- Medical Diagnostics
Background:
- Diagnosing periprosthetic joint infection (PJI) remains challenging due to the lack of a perfectly accurate diagnostic test.
- An ideal solution involves using an existing synovial indicator for PJI detection without additional costs.
- Synovial absolute neutrophil count (ANC) was hypothesized to enhance PJI diagnostic accuracy.
Purpose of the Study:
- To evaluate the diagnostic utility of synovial absolute neutrophil count (ANC) for chronic knee and hip periprosthetic joint infection (PJI).
- To determine if synovial ANC can improve the accuracy of PJI diagnosis in orthopedic surgery patients.
Main Methods:
- A cohort of 260 patients undergoing joint aspiration for PJI workup was analyzed.
- Data included patient demographics, procedure type, and synovial fluid analysis (WBC count, differential, α-defensin).
- Synovial fluid absolute neutrophil count (ANC) was calculated and correlated with PJI diagnosis.
Main Results:
- Synovial ANC demonstrated high diagnostic performance with an area under the receiver operating characteristic curve (AUC) of 0.930 for knee PJI at a threshold of 1,415.5 cells/μL.
- For hip PJI, the AUC was 0.905 with an optimal threshold of 2,247 cells/μL.
- These findings indicate strong discriminatory power for both knee and hip PJI.
Conclusions:
- Synovial absolute neutrophil count (ANC) is a valuable and efficient marker for diagnosing periprosthetic joint infection (PJI).
- This approach aids in ruling out PJI, providing crucial information through standard diagnostic tests.
- The study supports the integration of synovial ANC into routine PJI diagnostic protocols.
