Retrospective Cohort Study
Copyright ©The Author(s) 2020. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Orthop. Jan 18, 2020; 11(1): 36-46
Published online Jan 18, 2020. doi: 10.5312/wjo.v11.i1.36
Good accuracy of the alpha-defensin lateral flow test for hip periprosthetic joint infection: A pilot study in a retrospective cohort of 52 patients
Jesse WP Kuiper, Pieter Pander, Stan J Vos
Jesse WP Kuiper, Stan J Vos, Department of Orthopedic Surgery, Noordwest Ziekenhuisgroep, Alkmaar 1815 JD, Netherlands
Pieter Pander, Centre for Orthopedic Research Alkmaar, Noordwest Ziekenhuisgroep, Alkmaar 1815 JD, Netherlands
Author contributions: Kuiper JWP, Pander P, Vos SJ designed research; Kuiper JWP, Pander P, Vos SJ performed research; Kuiper JWP, Pander P analyzed data; Kuiper JWP, Pander P, Vos SJ wrote the paper.
Institutional review board statement: This study was reviewed and approved by the Ethics Committee of the Noordwest Ziekenhuisgroep.
Informed consent statement: Patients were not required to give informed consent to the study because the analysis used anonymous clinical data that were obtained after each patient agreed to treatment by written consent.
Conflict-of-interest statement: All authors declare no conflicts of interest related to this article.
Data sharing statement: No additional data are available.
STROBE statement: The manuscript was prepared and revised according to the STROBE Statement-checklist of items.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Corresponding author: Jesse WP Kuiper, MD, MSc, Department of Orthopedic Surgery, Noordwest Ziekenhuisgroep, Wilhelminalaan 12, Alkmaar 1815 JD, Netherlands. jwp.kuiper@gmail.com
Received: March 25, 2019
Peer-review started: March 26, 2019
First decision: June 11, 2019
Revised: October 18, 2019
Accepted: November 7, 2019
Article in press: November 7, 2019
Published online: January 18, 2020
Processing time: 290 Days and 9.5 Hours
ARTICLE HIGHLIGHTS
Research background

Periprosthetic joint infection (PJI) is one of the most severe complications after hip arthroplasty. Therefore, it is important to diagnose this problem accurately. Several diagnostic criteria are currently used for PJI diagnosis.

Research motivation

One of the newest additions to the diagnostic options is the determination of alpha-defensin, a protein released by white blood cells in synovial fluid. Two tests are available, the lateral flow test being the fastest (point of care) test. This test of aspirated joint fluid has not yet been extensively studied.

Research objectives

The objective was to identify a cohort of patients after hip arthroplasty in whom the alpha-defensin lateral flow (ADLF) test was already performed in the last two years in our hospital, and to assess the accuracy of the ADLF test for this cohort.

Research methods

The database of patients after total hip arthroplasty who underwent aspiration and ADLF testing was checked and data were retrospectively collected and analyzed. All patients underwent sterile aspiration of the hip joint as part of the diagnostic work-up for painful or poor functioning hip arthroplasty, between January 2015 and March 2018. Three recent definitions of PJI for calculation of test accuracy were used. The Musculoskeletal Infection Society (MSIS) definition was used as the standard. European Bone and Joint Infection Society (EBJIS) and International Consensus Meeting (ICM) definitions were also used for comparison.

Research results

A total of 52 patients (52 aspirations) were included in this pilot study. In 11 patients (21%) the ADLF test was positive. According to the MSIS criteria, 6 patients had a PJI. Using these criteria, sensitivity was 100% (CI: 54%-100%), specificity was 89% (CI: 76%-96%), positive predictive value (PPV) was 55% (CI: 34%-73%) and negative predictive value (NPV) was 100%. When adhering to the criteria by the EBJIS, PJI was found in 14 patients and the ADLF test had a sensitivity of 71% (CI: 42%-92%), specificity of 97% (CI: 86%-100%), PPV of 91% (CI: 58%-99%) and NPV of 90% (CI: 80%-96%).

When using the 2018 ICM criteria and classifying inconclusive cases as infected, sensitivity was 91% (62%-100%), specificity 100% (91%-100%). PPV, NPV and accuracy were 100%, 98% (86%-100%) and 98% (90%-100%), respectively.

Research conclusions

The diagnostic accuracy of the ADLF test for hip arthroplasty was high: Sensitivity was 100%, specificity 89%. Using different PJI diagnosis criteria, overall accuracy remained 90% or higher. These results are comparable to prior findings by other authors. Caution should be taken when when interpreting the results of the ADLF test in metallosis cases, as metallosis may cause false positive results.

Research perspectives

This study confirms the good clinical test results for the ADLF test found by others. However, the use of the ADLF test in cases of suspected PJI in hemi-arthroplasty or metal-on-metal has not been studied well, and one should be careful not to rely solely on the ADLF test, especially in those cases.