Periprosthetic joint infection (PJI) remains a major clinical challenge. In this study, we evaluated the diagnostic performance of lipocalin-2 (LCN2), a well-characterized neutrophil protein, in synovial fluid to discriminate PJI and aseptic implant failure.
Synovial fluid from patients with acute or chronic PJI, aseptic failure, or controls was obtained during surgery. LCN2 was quantified using a modified enzyme immunoassay coupled with chemiluminescence (Architect Urine NGAL; Abbott Laboratories).
Synovial fluid was collected from 72 patients: 22 (30.6%) proven infections, 22 (30.6%) aseptic implant failures, and 28 (38.8%) controls. Synovial fluid was obtained from the hip in 18 (25%) and knee in 54 (75%) cases. Among infections, there were 16 (22.2%) acute and 6 (8.3%) chronic PJIs. The median (interquartile range) LCN2 concentration in synovial fluid was 1536.5 ng/mL (261.8-12,923) in the infection group, 87.0 (54.8-135) in the aseptic group, and 55 (45-67.8) in the control group (P < .001). LCN2 discriminated nearly perfectly between controls and confirmed infection (area under the receiver operating characteristic 0.98, 95% confidence interval 0.95-1.00). The optimal cut-off value for maximal sensitivity (86.3%) and specificity (77.2%) to discriminate aseptic failure versus proven infection was 152 ng/mL, with an area under the receiver operating characteristic of 0.92 (95% confidence interval 0.84-0.99).
LCN2 is a potential novel biomarker that may be helpful to inform surgical teams on the potential risk of PJI and optimize specific surgical interventions as it distinguishes between septic and aseptic failure of prosthesis with high sensitivity and specificity.