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Published on: December 3, 2017
Diagnostic Accuracy of Alpha Defensin Lateral Flow Assay in Total Hip and Knee Arthroplasty
Mark Wu1, Brett R Bukowski1, Joel A Hickman2
1Department of Orthopedic Surgery, Mayo Clinic, Rochester, Minnesota.
Background:
Accurate diagnosis of periprosthetic joint infection (PJI) remains suboptimal. Of the tests used, one is the alpha defensin lateral flow assay (ADLFA). This study assessed ADLFA for the diagnosis of PJI in total hip arthroplasties (THAs) and total knee arthroplasties (TKAs). We hypothesized that ADLFA would have high specificity and sensitivity for diagnosing PJI, but that certain clinical features would influence test reliability.
Methods:
We reviewed 473 ADLFA tests from 141 THAs and 332 TKAs performed from 2020 to 2023 at a single institution. The mean age was 66 years, 51% were women, and mean body mass index was 32. There were 142 PJIs (2018 Musculoskeletal Infection Society criteria excluding ADLFA). Overall, 49% were primary and 51% revision procedures, 22% were on antibiotics within two weeks of arthrocentesis, 18% had an inflammatory arthropathy, and 7% had an in situ spacer.
Results:
The overall sensitivity, specificity, positive predictive value, and negative predictive value of ADLFA were 80, 97, 92, and 92%, respectively. There were 6% (29 of 473) that had false negative results, of which 38% were on antibiotics within two weeks of arthrocentesis and 21% of which were spacer aspirations. The negative predictive value was lower for those who had recent antibiotic use (76%) compared to those who did not (94%; P < 0.001). There was lower sensitivity (57%) for spacer compared to nonspacer aspirations (82%; P = 0.04). Furthermore, sensitivity in THA (67%) was lower compared to TKA (84%; P = 0.033). In TKAs, there was lower specificity (91%) for those who had inflammatory arthropathies (99%; P = 0.02).
Conclusions:
The ADLFA is highly specific in diagnosing PJI and is less sensitive in patients who have antibiotic spacers and those who have THAs compared to TKAs. Additionally, underlying inflammatory arthropathies may decrease specificity, yielding false positive results, specifically in TKAs.
Insights
The alpha defensin lateral flow assay (ADLFA) shows high specificity for diagnosing periprosthetic joint infection (PJI). However, its sensitivity is reduced in patients with antibiotic spacers or those undergoing total hip arthroplasty (THA).
Area of Science:
- Orthopedic Surgery
- Infectious Diseases
- Diagnostic Medicine
Background:
- Accurate diagnosis of periprosthetic joint infection (PJI) is critical but remains challenging.
- The alpha defensin lateral flow assay (ADLFA) is a diagnostic tool for PJI.
- Understanding factors influencing ADLFA reliability is essential for clinical application.
Purpose of the Study:
- To assess the diagnostic performance of ADLFA for PJI in total hip arthroplasties (THAs) and total knee arthroplasties (TKAs).
- To evaluate the impact of specific clinical features on ADLFA sensitivity and specificity.
Main Methods:
- Retrospective review of 473 ADLFA tests from 141 THAs and 332 TKAs.
- Analysis included patient demographics, procedure types (primary/revision), antibiotic use, inflammatory arthropathy, and in situ spacers.
- Diagnosis of PJI based on 2018 Musculoskeletal Infection Society criteria (excluding ADLFA).
Main Results:
- Overall ADLFA performance: 80% sensitivity, 97% specificity, 92% PPV, 92% NPV.
- Lower NPV (76%) observed in patients with recent antibiotic use compared to those without (94%).
- Reduced sensitivity for spacer aspirations (57%) and THAs (67%) compared to non-spacer aspirations (82%) and TKAs (84%).
- Lower specificity (91%) in TKAs with inflammatory arthropathies compared to those without (99%).
Conclusions:
- ADLFA demonstrates high specificity for PJI diagnosis.
- ADLFA sensitivity is compromised in patients with antibiotic spacers and in THAs versus TKAs.
- Inflammatory arthropathies may decrease specificity, potentially leading to false positives in TKAs.
