SAT0382 Utility of neutrophil cd64 & serum trem-1 in distinguishing bacterial infection from disease flare in sle and anca associated vasculitis. (12th June 2018) - Ajmani, S.
Abstract : Background: Treating physician is challenged to differentiate between disease activity vs. infection as to the cause of fever in patients with SLE and ANCA associated vasculitis (AAV). Presently, there is no biomarker to reliably differentiate between them. Objectives: We aimed to determine the usefulness of CD64 (FcγR1) expression on neutrophils and sTREM-1 (soluble triggering receptor expressed on myeloid cells) in serum in distinguishing bacterial infection from disease flare in SLE and AAV. Methods: 20 healthy controls and patients of SLE and AAV admitted to our unit either with disease flare or bacterial infection were recruited over a period of 1 year. Neutrophil CD64 expression was measured by flow cytometry and sTREM by ELISA from blood samples collected on the day of admission. Results: Among the 76 patients included in the study 51 (SLE-35 and AAV-16) had disease flare while 25 (SLE-21 and AAV-4) had infection. 72% had fever at presentation. The percentage of neutrophils with CD64 expression and their mean fluorescence intensity in patients with infection were significantly (p<0.05) higher as compared to those without infection and controls (Table-1). The sensitivity and specificity of CD64 expression on neutrophils to diagnose bacterial infection (using a cut off value of 30%) was 85% and 84%, respectively. Whereas, the sensitivity and specificity of procalcitonin was 75% and 85% respectively. There was no significant difference in soluble TREM-1 levels between the two groups. Total leucocyte count (TLC), ESR, CRP, C3, C4 levels were not significantly different between disease flare and infection group. On subgroup analysis (Table-2) patients of SLE with infection had a higher CRP, TLC and Procalcitonin compared to those with disease flare (p<0.5). ROC curves are depicted in figure 1. Conclusions: CD64 expression on neutrophils is helpful in differentiating bacterial infection from disease flare in patients with SLE and AAV. Disclosure of Interest: None declared