The Alpha-defensin Test for Periprosthetic Joint Infections Is Not Affected by Prior Antibiotic Administration

Abstract

BackgroundPrevious studies have demonstrated that the administration of antibiotics to patients before performing diagnostic testing for periprosthetic joint infection (PJI) can interfere with the accuracy of test results. Although a single-institution study has suggested that alpha-defensin maintains its concentration and sensitivity even after antibiotic treatment, this has not yet been demonstrated in a larger multiinstitutional study.Questions/purposes(1) For the evaluation of PJI, is prior antibiotic administration associated with decreased alpha-defensin levels? (2) When prior antibiotics are given, is alpha-defensin a better screening test for PJI than the traditional tests (erythrocyte sedimentation rate [ESR], C-reactive protein [CRP], fluid white blood cells, fluid polymorphonuclear cells [PMNs], and fluid culture)?MethodsThis retrospective study included data from 106 hip and knee arthroplasties with Musculoskeletal Infection Society-defined PJI from four centers. Of the 106 patients in this study, 30 (28%) were treated with antibiotics for PJI before diagnostic workup (ABX group), and 76 (72%) were not treated before the diagnostic workup (NO-ABX group). There were no differences in age, sex, joint, culture-negative rate, or bacteriology between groups. The patients in the ABX group had antibiotics initiated by physicians who commenced care before assessment for PJI by the treating surgeon’s service. We compared the alpha-defensin levels and sensitivity between the ABX and NO-ABX groups. Additionally, the sensitivity of the alpha-defensin test was compared to that of traditional tests for PJI among patients on antibiotics.ResultsThe administration of antibiotics before performing the alpha-defensin test for PJI was not associated with a decreased median alpha-defensin level (ABX group, median 4.2 [range, 1.79–12.8 S/CO] versus NO-ABX, median 4.9 [range, 0.5–16.8 S/CO], difference of medians: 0.68 S/CO [95% confidence interval {CI}, −0.98 to 1.26], p = 0.451). Furthermore, the alpha-defensin test had a higher sensitivity (100%; 95% CI, 88.4%–100.0%) in diagnosing PJI among patients on antibiotics when compared with the ESR (69.0% [95% CI, 49.17%–84.72%], p = 0.001), the CRP (79.3% [95% CI, 60.3%–92.0%], p = 0.009), the fluid PMN% (79.3% [95% CI, 60.3%–92.0%), p = 0.009), and fluid culture (70.0% [95% CI, 50.6%–85.3%], p = 0.001).ConclusionsThe alpha-defensin test maintains its concentration and sensitivity for PJI even in the setting of antibiotic administration. Furthermore, among patients with PJI on antibiotics, the alpha-defensin tests demonstrated a higher sensitivity in detecting PJI when compared with the ESR, CRP, fluid PMN%, and fluid culture. The high sensitivity of the alpha-defensin test, even in the setting of prior antibiotic treatment, provides excellent utility as a screening test for PJI.Level of EvidenceLevel III, diagnostic study.

Inflammatory disorders mimicking periprosthetic joint infections may result in false-positive α-defensin

“…This result is in line with a study by Kasparek et al, who demonstrated a low sensitivity of 67% [17]. In one case (see Supplementary Table S1, knee 37) with a 'culture-negative PJI', the a-defensin result switched from positive preoperatively to negative intraoperatively after 2 days of antibiotic treatment, even though a previous antibiotic treatment has not been considered a concern [12,18].…”

What’s New in Musculoskeletal Infection: Update Across Orthopaedic Subspecialties

“…Culture technique was improved by using blood culture bottles 49 , and longer duration of culture growth led to higher detection of P. acnes 50 . Over the past year, studies further evaluated other synovial fluid markers including procalcitonin, a-defensin, and leukocyte esterase [51][52][53][54][55] . The a-defensin lateral flow test introduced in Europe demonstrated findings similar to those of intraoperative frozen sections, with a sensitivity of 67% and a specificity of 93% 56 .…”

CORR Insights®: How Reliable Is the Alpha-Defensin Immunoassay Test for Diagnosing Periprosthetic Joint Infection? A Prospective Study

“…The authors concluded that if the alpha-defensin test is negative, then ''it is quite likely that the pain in the joint after THA or TKA is not caused by PJI.'' Previous studies [5][6][7]12] …”

“…A rapid molecular test that would provide the species of bacteria and drug sensitivity would be even better. Finally, the cell biology of alpha-defensin release, most likely from macrophages in some cases of metallosis, and the modulation of macrophage proinflammatory cytokine release by alpha defensins [12] are of interest with respect to the basic science of inflammation and the various adverse local tissue reactions associated with failed arthroplasty.…”