Synovial calprotectin accurately predicts knee Periprosthetic joint infection

Italy: Periprosthetic joint infection (PJI) is a devastating complication after joint replacement surgery, and making diagnosis is often far from obvious. Calprotectin was recently proposed as a promising synovial biomarker to detect PJI.

M. Grassi et al noted that there were no comparative study between enzyme-linked immunosorbent assay (ELISA) and rapid calprotectin test (CalFAST).

The authors compared these methods with leukocyte esterase (LE) test from synovial fluid of painful knee arthroplasty subjected to infectious workup.

Methods: Ninety-three patients were included in this prospective observational study. They underwent synovial fluid aspiration that was analyzed for cell count, microbiological culture, LE test, calprotectin rapid test, and calprotectin immunoassay dosage. The 2018 Consensus Statements criteria for PJI were used to diagnose PJI. Sensitivity, specificity, positive and negative likelihood ratio, and receiver operating characteristic were calculated for detection methods and compared.

Results:

• They categorized 39 patients as infected and 50 patients as not infected.

• The sensitivity comparing the ELISA test and CalFAST test was similar, 92.3% and 97.4%, respectively.

• LE rapid test showed 46% of sensitivity and 94% of specificity.

• The highest specificity was found with ELISA test (100%).

• Comparing the receiver operating characteristic curves by z-test, there were statistically significant differences between LE strip test and the other two methods.

• No statistically significant differences were present between ELISA and CalFAST test.

The authors concluded that - synovial calprotectin detection has high accuracy in knee PJI diagnosis, both ELISA and rapid test. LE strip test remains a good test to confirm the diagnosis of PJI in case of positivity. In clinical practice, the calprotectin rapid test can be considered an excellent point-of-care test.

Key Words: periprosthetic joint infection, diagnosis, calprotectin, synovial fluid, total knee arthroplasty knee

Further reading:

Synovial Biomarkers to Detect Chronic Periprosthetic Joint Infection: A Pilot Study to Compare Calprotectin Rapid Test, Calprotectin ELISA Immunoassay and Leukocyte Esterase Test

Marco Grassi, Paolo Salari, Luca Farinelli, Marco D'Anzeo, Nicoletta Onori, Antonio Gigante.

The Journal of Arthroplasty 37 (2022) 781-786

https://doi.org/10.1016/j.arth.2021.12.040