Study of the Validity of Neutrophil CD64 and Serum Procalcitonin as Diagnostic Markers to Discriminate Infection from Disease Activity in Patients with Systemic Lupus Erythematosus

Abstract

Introduction: In addition to the complexity of the clinical presentation of both infections and disease activity in systemic lupus erythematosus (SLE) patients, the difficulty in making the therapeutic decision require investigations that should be of diagnostic value. Neutrophil CD64 is up regulated within few hours in patients with infection. Similarly, serum procalcitonin (PCT) levels increase rapidly following bacterial infection. Objective: The aim of this work is to study the usefulness of neutrophil CD64 expression and serum PCT as diagnostic markers to discriminate infection from disease activity in patients with systemic lupus erythematosus. Methods: This study was carried on 20 healthy females as controls (group I) and 55 female patients with SLE. Patients were distributed as following; 20 SLE patients without activity or infections (group II), 20 SLE patients with lupus activity (group III), and 15 SLE patients with infection (group IV). CBC, ANA, Anti-ds DNA, C3 and C4 were measured in all population. Serum PCT was measured by ELFA and neutrophil CD64 expression was done by flowcytometry. Results: Neutrophil CD64 expression and serum PCT levels were increased significantly in SLE patients with infection compared to those with disease activity. We demonstrated significant correlations between CD64 and markers of both activity and infection, while serum PCT levels were significantly correlated with markers of infection. The area under the ROC curves for detection of infection (AUC; 95% CI) for neutrophil CD64 expression and serum PCT were (0.90; 0.79-1.01) and (0.99; 0.95-1.01), respectively. Conclusion: Our findings can prove that both neutrophil CD64 and serum PCT are reliable markers to discriminate infection from disease activity in SLE patients. Serum PCT was more accurate than neutrophil CD64 expression.