Abstract
Aim
To assess the analytical performance and to establish the cut-off of synovial fluid D-lactate concentration for the diagnosis of prosthetic joint infection (PJI) and septic arthritis (SA) using commercial kits provided by two manufacturers (A and B).
Method
We prospectively included patients with native or prosthetic joints undergoing synovial fluid aspiration as routine diagnostic procedure. Among 224 patients with prosthetic joints, 137 patients had aseptic loosening (AL) and 87 were diagnosed with PJI. Among 71 patients with native joints, 39 were diagnosed with osteoarthrosis (OA) and 32 with SA.
Results
Kits for the measurement D-lactate provided by the manufacturer A.
Patients with prosthetic joints
The mean D-lactate concentration was significantly higher in patients with PJI than with AL (2.33 vs 0.77 mMol, respectively; p<0.0001). The optimal D-lactate cut off was 1.2 mmol/l (sensitivity = 97.7%, specificity = 83.9%, PPV = 79.4%, NPV = 98.3%; AUC = 0.99).
Patients with native joints
We found significantly higher concentration of D-lactate in patients with SA compared to OA (2.27 vs 0.46 mMol, respectively; p<0.0001). The optimal D-lactate cut off was 1.2 mmol/l (sensitivity = 93.8%, specificity = 94.9%, PPV = 93.7%, NPV = 94.9%; AUC = 0.99).
Kits for the measurement D-lactate provided by the manufacturer B.
Patients with prosthetic joints
The difference between concentration of D-lactate in patients with PJI and AL was also significant (mean, 2.5 vs 0.04 mmol/L, respectively; p<0,0001). The optimal D-lactate cut off was 0.5 mmol/L (sensitivity = 94.7%, specificity = 92,0%, PPV = 85.7%, NPV = 97.1%; AUC = 0.99).
Patients with native joints
Significantly higher concentration of D-lactate in patients with SA in comparison with OA (mean, 2.0 vs 0.28 mmol/L, respectively; p<0.0001). The optimal D-lactate cut off was 0.5 mmol/L (sensitivity = 100%, specificity = 92.0%, PPV = 81.8%, NPV = 100%; AUC = 0.99)
Conclusions
The synovial fluid D-lactate test shows high analytical performance and diagnostic capabilities in the diagnosis of PJI and SA. The optimal cut-off for the diagnosis of infection differ between manufactures. Synovial fluid D-lactate is reliable bacterial-specific marker for diagnosis of PJI and SA.
