Diagnostic accuracy study of globular sedimentation rate and C-reactive protein in patients with systemic lupus erythematosus and fever admitted to a Social Security hospital in Lima, Peru, 2010–2019

Abstract

IntroductionIn patients with systemic lupus erythematosus (SLE) and fever, the causes are infection and/or activity. We assessed the diagnostic accuracy of C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) to discern these causes. MethodsWe reviewed medical records of patients with SLE and fever hospitalized from 2010 to 2019. Based on two categories of cause of fever (infection with-or-without activity versus activity alone), we computed ROC curves, areas under the curve (AUC) and best cut-off values for ESR, parameter ESR, CRP and ESR/CRP ratio. In addition, we calculated sensitivity, specificity, and predictive values. ResultsWe included 40 cases (34 women) with an average age of 35.5 years. The main cause of fever was the coexistence of infection and activity (17/40; 43%), followed by fever only due to activity (14/40; 35%). The most frequent infection was pneumonia (10/40; 25%) and the most common activity was renal (21/40; 53%). To diagnose “fever due to infection with-or-without activity”, compared to “fever only due to activity”, CRP had an AUC: 0.86 (95% CI: 0.75–0.97) with 5.4 mg/dl as the best cut-off value (Se: 76.9%; Sp: 85.7%; PPV: 90.9; NPV: 66.6%). To diagnose “fever due to activity only”, compared to “fever due to infection with or without activity”, the ESR/CRP ratio had an AUC: 0.83 (95% CI: 0.68–0.98) with 21.42 as the best cut-off value (Se: 78.6%; Sp: 84.6%; PPV: 73.3%; NPV: 88.0%). ConclusionCRP and ESR/CRP ratio, which are routine tests in these cases, are potentially useful in discerning causes of fever in SLE patients. These findings should be confirmed in future studies.