New parameters available on Sysmex XE-5000 hematology analyzers contribute to differentiating dengue from leptospirosis and enteric fever.

INTRODUCTION: Distinguishing dengue virus infection from other febrile thrombocytopenic illnesses such as leptospirosis or enteric fever is important but difficult, due to the unavailability of reliable diagnostic tests. Sysmex XE-5000 hematology analyzers use fluorescence flow cytometry to quantitate new parameters including cells in the atypical lymphocyte area (AL), high-fluorescent lymphocyte counts (HFLC), immature granulocytes (IG), and immature platelets (IPF). This study aimed to investigate whether these parameters can help to discriminate between the diseases. MATERIAL AND METHODS: We compared hematocytometry performed by a Sysmex XE-5000 analyzer in Indonesian adults with dengue (n = 93), leptospirosis (n = 11), and enteric fever (n = 6) infection, and in healthy controls (n = 28). RESULTS: Receiver operating characteristic curves comparing dengue and leptospirosis showed that dengue was characterized by increased %AL (AUC 0.87; 95% CI 0.70-1.03), %HFLC (AUC 0.89; 95% CI 0.78-0.99), and %IPF (AUC 0.81; 95% CI 0.65-0.97), while patients with leptospirosis had increased %IG (AUC 0.86; 95% CI 0.71-1.02). Low %AL, %HFLC, and %IG supported a diagnosis of enteric fever. CONCLUSIONS: The detection of AL, HFLC, IG, and IPF by Sysmex XE-5000 hematology analyzers can help to differentiate between common causes of febrile illnesses with thrombocytopenia in dengue endemic areas. We recommend further investigating the discriminatory value of these parameters in clinical practice.

Platelet function alterations in dengue are associated with plasma leakage.

Severe dengue is characterised by thrombocytopenia, plasma leakage and bleeding. Platelets are important for preservation of endothelial integrity. We hypothesised that platelet activation with secondary platelet dysfunction contribute to plasma leakage. In adult Indonesian patients with acute dengue, we measured platelet activation status and the response to the platelet agonist TRAP using flow cytometer-based assays. Patients were monitored daily for plasma leakage by ultrasonography. Acute dengue was associated with platelet activation with an increased expression of the activated fibrinogen receptor (αIIbß3), the lysosomal marker CD63 and the alpha-granule marker CD62P (P-selectin). Upon maximal platelet activation by TRAP, platelet function defects were observed with a significantly reduced maximal activated αIIbß3 and CD63 expression and reduced platelet-monocyte and platelet-neutrophil complexes. Patients in the lowest tertile of activated αIIbß3 and CD63 expression had an odds ratio for plasma leakage of 5.2 (95% confidence interval [CI] 1.3-22.7) and 3.9 (95% CI 1.1-13.7), respectively, compared to the highest tertile. Platelet-derived serotonin has previously been related to plasma leakage and we found increased intra-platelet serotonin concentrations in our patients. In conclusion, platelet activation with platelet function alterations can be found in patients with acute dengue and this may contribute to dengue-associated plasma leakage.