The interest of inflammatory biomarkers in the diagnostic approach in an internal medicine department: A cross-sectional study

Abstract

Background The role of inflammatory biomarkers in etiological orientation is increasingly under study, and their potential significance is recognized. Given the diversity of diseases managed in internal medicine and the delayed results of microbiological tests, clinicians often face challenges in the diagnostic approach. This study aimed to describe the biomarkers’ role in distinguishing between infectious and noninfectious diseases and define their thresholds for infections. Methods Procalcitonin (PCT), neutrophil-to-lymphocyte-ratio (NLR), C-reactive-protein (CRP), fibrinogen, ferritinemia and lactate were measured on admission in all patients admitted to the Internal Medicine Department of Sahloul Hospital, over a 7-month period. The optimal cut-off values for the sensitivities and specificities to the infectious diseases were determined using receiver operating characteristic (ROC) curve analysis and Youden’s index. The diagnostic accuracy of biomarkers for predicting infectious etiologies was calculated by area under the curve (AUC). Results Overall, 164 patients were included of whom 32.3% had infectious diseases. The high mean levels of leukocytes (12,047 cells/mm3), NLR (9.7), CRP (152.5 mg/L), PCT (3.28 ng/ml) and fibrinogen (5.37g/L) were significantly linked to infectious etiologies. We identified cut-offs of NLR (6.1), CRP (123mg/L), PCT (0.24ng/mL) and fibrinogen (4.9g/L) to discriminate infectious etiologies in our population. For diagnosing infectious diseases, the CRP showed higher AUC (Sp:89.7%, Se:64.3%, AUC=0.9, 95% CI: 0.83, 0.96; p<10-3) than PCT (Sp:86.1%, Se:62.3%, AUC=0,87, 95% CI: 0.80, 0.93; p<10-3), NLR (Sp:87.1%, Se:61%, AUC=0.81, 95% CI: 0.731, 0.902; p<10-3) and fibrinogen (Sp:84.7%, Se:68.3%, AUC=0.77, 95% CI: 0.65, 0.98; p<10-3). The combination of CRP and NLR levels improved the diagnostic accuracy (AUC=0.93, 95% CI: 0.84, 0.96; p<10-3) for distinguishing between infectious and non-infectious diseases. Conclusions Our study showed the usefulness of inflammatory biomarkers, particularly the NLR and its combination with CRP, which are low cost and easy to assess, in promoting the diagnostic accuracy to distinguish infections among other diagnoses.