Role of Extended White Blood Cell Parameters in Distinguishing Acute Febrile Illnesses

Introduction: Acute febrile illness contributes to significant morbidity and death particularly in tropical country such as Indonesia. The symptoms are nonspecific, therefore distinguishing these pathogens is difficult without additional laboratory tests. The extended white blood cell parameters indicate cell activities induced by immune response to infection. The study aims to explore the profile of extended white blood cell parameters in acute febrile illnesses and evaluate their diagnostic power to differentiate etiologies of acute febrile illnesses. Methods: This study was a cross-sectional analytical study with a total of 473 samples, conducted between October 2022 and 2023 at Siloam Hospitals Lippo Village, Banten, Indonesia. Acute febrile illnesses are included in this study, including dengue infection, chikungunya infection, typhoid infection, and other bacterial infections. The extended white blood cell parameters including high fluorescence lymphocyte count (HFLC), immature granulocyte (IG), neutrophil-to-lymphocyte ratio (NLR), and cell population data (CPD) which were NE-SSC, NE-SFL, NE-WY, LY-X, LY-Y, and LY-WY. These parameters were integrated in a routine hematology test as research parameters, performed by Sysmex XN2000. Data were analyzed using SPSS Version 25. Results: The value of extended white blood cell parameters was found to be significantly different in viral and bacterial infection (HFLC 1.10% (0.30%-3.85%) vs. 0.20% (0.10%-0.70%), p < 0.001; IG 0.4% (0.2%-0.6%) vs. 0.5% (0.3%-1.1%), p < 0.001; NLR 1.93 (1.10-3.47) vs. 5.21 (2.20-12.26), p < 0.001; NE-SFL 47.7 (45.95-50.10) vs. 48.6 (45.82-52.57), p=0.020; NE-WY 622 (585-653) vs. 653 (615-747), p < 0.001; LY-Y 66.4 (63.85-69.75) vs. 64.05 (60.52-67.17), p < 0.001). HFLC and LY-Y had statistically significant AUC 0.753 and 0.646, respectively, (p < 0.001) in the dengue infection group. IG, NLR, NE-WY, and NE-SFL had statistically significant AUC in bacteremia (0.806, 0.876, 0.783, and 0.656, respectively). Conclusion: HFLC was a useful diagnostic tool to identify viral infection, particularly dengue infection, while IG, NLR, NE-SFL, and NE-WY can be useful to differentiate bacteremia from other acute febrile illnesses.