The performance of clinical indicators such as C-reactive protein (CRP), neutrophil-lymphocyte ratio (NLR), and platelet-lymphocyte ratio (PLR) in the identification of infection in (SLE) Systemic Lupus Erythematosus patients was examined by the researchers for a medical records review research. A total of 104 patients with SLE were hospitalized between 2014 and 2018, and were divided into 3 groups: infection, infection and disease activity, and isolated disease activity. Clinical and laboratory characteristics were compared between groups. CRP, NLR, and PLR accuracy metrics were computed. 

CRP (56 vs 26 vs 15 mg/dL, P=0.002), NLR (7.9 vs 4.0 vs 3.1, P=0.005), and PLR (270 vs 227 vs 134, P=0.025) were found to differ between the groups, with higher values in the infected group, intermediate values in the mixed group, and lower values in the group with isolated activity—CRP (56 vs 26 Fever, tachypnea, and PLR were all linked to infection in different ways. The sensitivity and specificity for the prediction of infection were 67% and 67%, 65% and 58%, and 71% and 53%, respectively, for the cutoff points of 20 mg/L, NLR of 3.5, and PLR of 151.4. For the diagnosis of infection, the established algorithm has a sensitivity of 86.6% and a specificity of 81%. 

The algorithm performed better when clinical and laboratory markers were used together than when they were used separately, indicating that it had a lot of promise for clinical usage.

Reference:journals.lww.com/jclinrheum/Abstract/2022/04000/Infection_in_Hospitalized_Patients_With_Systemic.1.aspx