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. 2020 Dec 7;1(12):737-742.
doi: 10.1302/2633-1462.112.BJO-2020-0166.R1.

Synovial fluid interleukin-6 is not superior to cell count and differential in the detection of periprosthetic joint infection

René Mihalič  1 , Jurij Zdovc  2 , Peter Brumat  1 , Rihard Trebše  1   3
Affiliations

Synovial fluid interleukin-6 is not superior to cell count and differential in the detection of periprosthetic joint infection

René Mihalič et al. Bone Jt Open. .

Abstract

Aims: Synovial fluid white blood cell (WBC) count and percentage of polymorphonuclear cells (%PMN) are elevated at periprosthetic joint infection (PJI). Leucocytes produce different interleukins (IL), including IL-6, so we hypothesized that synovial fluid IL-6 could be a more accurate predictor of PJI than synovial fluid WBC count and %PMN. The main aim of our study was to compare the predictive performance of all three diagnostic tests in the detection of PJI.

Methods: Patients undergoing total hip or knee revision surgery were included. In the perioperative assessment phase, synovial fluid WBC count, %PMN, and IL-6 concentration were measured. Patients were labeled as positive or negative according to the predefined cut-off values for IL-6 and WBC count with %PMN. Intraoperative samples for microbiological and histopathological analysis were obtained. PJI was defined as the presence of sinus tract, inflammation in histopathological samples, and growth of the same microorganism in a minimum of two or more samples out of at least four taken.

Results: In total, 49 joints in 48 patients (mean age 68 years (SD 10; 26 females (54%), 25 knees (51%)) were included. Of these 11 joints (22%) were infected. The synovial fluid WBC count and %PMN predicted PJI with sensitivity, specificity, accuracy, PPV, and NPV of 82%, 97%, 94%, 90%, and 95%, respectively. Synovial fluid IL-6 predicted PJI with sensitivity, specificity, accuracy, PPV, and NPV of 73%, 95%, 90%, 80%, and 92%, respectively. A comparison of predictive performance indicated a strong agreement between tests.

Conclusions: Synovial fluid IL-6 is not superior to synovial fluid WBC count and %PMN in detecting PJI.Level of Evidence: Therapeutic Level IICite this article: Bone Jt Open 2020;1-12:737-742.

Keywords: IL-6; Interleukin-6; PJI; Periprosthetic joint infection; Synovial fluid.

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Conflict of interest statement

ICMJE COI statement: R. M., J. Z. and P. B. declare no conflict of interests. R.T. is the current president of The European Bone and Joint Infection Society (EBJIS).

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