The routine use of synovial alpha-defensin is not necessary
Derek F Amanatullah1, Robin Z Cheng1, James I Huddleston Iii1
1Department of Orthopaedic Surgery, Stanford University School of Medicine, Redwood City, California, USA.
Aims:
To establish the utility of adding the laboratory-based synovial alpha-defensin immunoassay to the traditional diagnostic work-up of a prosthetic joint infection (PJI).
Methods:
A group of four physicians evaluated 158 consecutive patients who were worked up for PJI, of which 94 underwent revision arthroplasty. Each physician reviewed the diagnostic data and decided on the presence of PJI according to the 2014 Musculoskeletal Infection Society (MSIS) criteria (yes, no, or undetermined). Their initial randomized review of the available data before or after surgery was blinded to each alpha-defensin result and a subsequent randomized review was conducted with each result. Multilevel logistic regression analysis assessed the effect of having the alpha-defensin result on the ability to diagnose PJI. Alpha-defensin was correlated to the number of synovial white blood cells (WBCs) and percentage of polymorphonuclear cells (%PMN).
Results:
Intraobserver reliability and interobserver agreement did not change when the alpha-defensin result was available. Positive alpha-defensin results had greater synovial WBCs (mean 31,854 cells/μL, SD 32,594) and %PMN (mean 93.0%, SD 5.5%) than negative alpha-defensin results (mean 974 cells/μL, SD 3,988; p < 0.001 and mean 39.4% SD 28.6%; p < 0.001). Adding the alpha-defensin result did not alter the diagnosis of a PJI using preoperative (odds ratio (OR) 0.52, 95% confidence interval (CI) 0.14 to 1.88; p = 0.315) or operative (OR 0.52, CI 0.18 to 1.55; p = 0.242) data when clinicians already decided that PJI was present or absent with traditionally available testing. However, when undetermined with traditional preoperative testing, alpha-defensin helped diagnose (OR 0.44, CI 0.30 to 0.64; p < 0.001) or rule out (OR 0.41, CI 0.17 to 0.98; p = 0.044) PJI. Of the 27 undecided cases with traditional testing, 24 (89%) benefited from the addition of alpha-defensin testing.
Conclusion:
The laboratory-based synovial alpha-defensin immunoassay did not help diagnose or rule out a PJI when added to routine serologies and synovial fluid analyses except in cases where the diagnosis of PJI was unclear. We recommend against the routine use of alpha-defensin and suggest using it only when traditional testing is indeterminate. Cite this article: Bone Joint J 2020;102-B(5):593-599.
Insights
Adding synovial alpha-defensin testing to prosthetic joint infection (PJI) diagnosis is only useful when traditional methods are inconclusive. This test aids in diagnosing or ruling out PJI in uncertain cases, improving diagnostic clarity.
Area of Science:
- Orthopedic Surgery
- Infectious Diseases
- Diagnostic Immunology
Background:
- Prosthetic joint infections (PJI) pose significant diagnostic challenges.
- Accurate and timely diagnosis is crucial for effective treatment and patient outcomes.
- Traditional diagnostic methods for PJI can sometimes yield indeterminate results.
Purpose of the Study:
- To evaluate the added value of a laboratory-based synovial alpha-defensin immunoassay in the diagnostic work-up of PJI.
- To determine if alpha-defensin testing improves diagnostic accuracy compared to traditional methods.
- To assess the utility of alpha-defensin in cases with unclear PJI diagnoses.
Main Methods:
- 158 patients undergoing work-up for PJI were evaluated by four physicians.
- Physicians reviewed diagnostic data, initially blinded to alpha-defensin results, then with results available.
- Multilevel logistic regression analyzed the impact of alpha-defensin on PJI diagnosis; correlation with synovial WBC and %PMN was assessed.
Main Results:
- Alpha-defensin testing did not change intraobserver or interobserver reliability.
- Positive alpha-defensin results correlated with significantly higher synovial white blood cells (WBCs) and polymorphonuclear cells (%PMN).
- Alpha-defensin did not alter PJI diagnosis when traditional testing was already conclusive, but it helped diagnose or rule out PJI in 24 of 27 (89%) indeterminate cases.
Conclusions:
- Synovial alpha-defensin immunoassay is not beneficial for routine PJI diagnosis when traditional tests are definitive.
- Alpha-defensin testing is valuable specifically in cases where PJI diagnosis remains unclear after initial assessment.
- Routine use of alpha-defensin is not recommended; its application should be reserved for indeterminate diagnostic scenarios.
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