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Study: Optimal threshold synovial fluid values for PJI of the hip are lower than previously reported
Recently published results showed optimal synovial fluid white blood cell count and polymorphonuclear cell percentage for diagnosing chronic periprosthetic joint infection of the hip was closer to thresholds for the knee compared with thresholds previously reported for the hip.
Javad Parvizi, MD, FRCS, and colleagues formed a cohort of 453 patients who underwent total hip arthroplasty revision at four different academic institutions and had a hip aspiration to determine synovial fluid cell count and polymorphonuclear cell (neutrophil) percentage (PMN%). Researchers defined periprosthetic joint infection (PJI) based on the Musculoskeletal Infection Society, and diagnosed 374 joints as aseptic and 79 joints as septic. Regardless of the suspicion for infection, researchers performed intraoperative aspirations as routine practice in 72% of patients.
Results showed a threshold for the diagnosis of chronic PJI of the hip of 3,966 cells/L for white blood cell count and 80% for PMN% in the overall cohort. Researchers found a notable institutional variation for fluid white blood cell count and PMN% despite the high predictive accuracy for the cohort. Patients with a white blood cell count of 3,000 to 5,000 cells/L had a PJI rate of 14% vs. a rate of 91% for patients with a white blood cell count of greater than 50,000 cells/L. Researchers also found patients with a PMN% of 75% to 85% had a PJI rate of 29% compared with a rate of 69% for patients with a PMN% of greater than 95%. – by Casey Tingle
Disclosures: Higuera reports that he receives grants from KCI, Stryker, CD Diagnostics, Orthofix, Cempra, Cymedica, OREF, Pacira and Myoscience; and personal fees from KCI, Covance, Pfizer and Zimmer Biomet. Please see the full study for a list of all other authors’ relevant financial disclosures.