A comparative study of intraoperative frozen section and alpha defensin lateral flow test in the diagnosis of periprosthetic joint infection

AbstractBackgroundMicrobiological diagnosis of prosthetic joint infection (PJI) relies on culture techniques that are slow and insensitive. Rapid tests are urgently required to improve patient management. Calprotectin is a neutrophil biomarker of inflammation that has been demonstrated to be effective for the diagnosis of PJI. A calprotectin based lateral flow test has been developed for the rapid detection of PJI using synovial fluid samples.MethodsA convenience series of 69 synovial fluid samples from patients at the Norfolk and Norwich University Hospitals (NNUH) were collected intraoperatively from 52 hip and 17 knee revision operations. Calprotectin levels were measured using a new commercially available lateral flow assay for PJI diagnosis (Lyfstone). For all samples, synovial fluid was pipetted onto the lateral flow device and the signal was read using a mobile phone app after 15 minutes incubation at room temperature.ResultsAccording to the Musculoskeletal Infection Society (MSIS) criteria, 24 patients were defined as PJI positive and the remaining 45 were negative. The overall accuracy of the lateral flow test against the MSIS criteria was 75%. The test had a sensitivity and specificity of 75% and 76% respectively with a positive predictive value (PPV) of 62% and a negative predictive value (NPV) of 85%. Discordant results were then reviewed by the clinical team using available patient data to develop an alternative gold standard for defining presence/absence of infection (MSIS+). Compared to MSIS+, the test showed an overall accuracy of 83%, sensitivity and specificity of 95% and 78% respectively, a PPV of 62% and an NPV of 98%. Test accuracy for hip revisions was 77% and for knee revisions was 100%.ConclusionsThis study demonstrates that the calprotectin lateral flow assay is an effective diagnostic test for PJI. Our data suggests that the test is likely to generate false positive results in patients with metallosis and gross osteolysis.

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Preliminary evaluation of a rapid lateral flow calprotectin test for the diagnosis of prosthetic joint infection

Bone and Joint Research ◽

10.1302/2046-3758.95.bjr-2019-0213.r1 ◽

2020 ◽

Vol 9 (5) ◽

pp. 202-210 ◽

Cited By ~ 1

Author(s):

Alexander J. Trotter ◽

Rachael Dean ◽

Celia E. Whitehouse ◽

Jarle Mikalsen ◽

Claire Hill ◽

...

Keyword(s):

Synovial Fluid ◽

Prosthetic Joint Infection ◽

Test Performance ◽

Predictive Value ◽

Joint Infection ◽

Lateral Flow ◽

Lateral Flow Assay ◽

Prosthetic Joint ◽

Flow Test ◽

Lateral Flow Test

Aims This pilot study tested the performance of a rapid assay for diagnosing prosthetic joint infection (PJI), which measures synovial fluid calprotectin from total hip and knee revision patients. Methods A convenience series of 69 synovial fluid samples from revision patients at the Norfolk and Norwich University Hospital were collected intraoperatively (52 hips, 17 knees) and frozen. Synovial fluid calprotectin was measured retrospectively using a new commercially available lateral flow assay for PJI diagnosis (Lyfstone AS) and compared to International Consensus Meeting (ICM) 2018 criteria and clinical case review (ICM-CR) gold standards. Results According to ICM, 24 patients were defined as PJI positive and the remaining 45 were negative. The overall accuracy of the lateral flow test compared to ICM was 75.36% (52/69, 95% CI 63.51% to 84.95%), sensitivity and specificity were 75.00% (18/24, 95% CI 53.29% to 90.23%) and 75.56% (34/45, 95% CI 60.46% to 87.12%), respectively, positive predictive value (PPV) was 62.07% (18/29, 95% CI 48.23% to 74.19%) and negative predictive value (NPV) was 85.00% (34/40, 95% CI 73.54% to 92.04%), and area under the receiver operating characteristic (ROC) curve (AUC) was 0.78 (95% CI 0.66 to 0.87). Patient data from discordant cases were reviewed by the clinical team to develop the ICM-CR gold standard. The lateral flow test performance improved significantly when compared to ICM-CR, with accuracy increasing to 82.61% (57/69, 95% CI 71.59% to 90.68%), sensitivity increasing to 94.74% (18/19, 95% CI 73.97% to 99.87%), NPV increasing to 97.50% (39/40, 95% CI 85.20% to 99.62%), and AUC increasing to 0.91 (95% CI 0.81 to 0.96). Test performance was better in knees (100.00% accurate (17/17, 95% CI 80.49% to 100.00%)) compared to hips (76.92% accurate (40/52, 95% CI 63.16% to 87.47%)). Conclusion This study demonstrates that the calprotectin lateral flow assay could be an effective diagnostic test for PJI, however additional prospective studies testing fresh samples are required. Cite this article: Bone Joint Res. 2020;9(5):202–210.

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