Background Differentiating systemic lupus erythematosus (SLE) flare from infection in febrile SLE patients is critical for deciding the treatment strategies. Since fever is the common symptom of systemic lupus erythematosus (SLE), it is uneasy to discriminate between SLE flare and infection. Delta neutrophil index (DNI) is a difference between leukocyte subfractions which corresponds to the fraction of immature granulocyte. Delta neutrophil index (DNI) was reported to be associated with infection and sepsis.
Objectives This study is performed to elucidate the possible role of DNI as a predictive marker in differentiating between disease activity and infection.
Methods A total of 92 febrile SLE patients with 111 episodes of admissions from January 2010 to February 2012 were retrospectively reviewed. Receiver operating characteristic (ROC) curve was used to identify the optimal cutoff value of DNI for differentiating SLE flare from infection. We used logistic regression to find independent variables for predicting infection among several clinical and laboratory markers.
Results The infection group showed higher white blood cell and neutrophil counts and higher levels of CRP and procalcitonin than the SLE flare group. Patients in the SLE flare group had significantly lower DNI than those in both infection groups, with and without bacteremia(p<0.001). In multivariate logistic regression analysis, only DNI was a significant independent factor for the presence of infection (OR 18.9). When we selected DNI value of 2.77% as the cutoff for infection, SLE patients with DNI ≥ 2.77% were found to have a higher risk for infection than those with DNI < 2.77% (Relative risk 8.48).
Conclusions The present study is the first report to evaluate DNI in febrile SLE patients, and investigates its usefulness as a novel serologic marker for differentiating SLE flare from infection. Our findings demonstrate that DNI measurement in febrile SLE patients is useful for predicting coexisting infectious episode and helpful in making decisions about the treatment.
Disclosure of Interest None Declared