Hematologic Parameters of Acute Dengue Fever Versus Other Febrile Illnesses in Ambulatory Returned Travelers

Point-of-care dengue diagnostics are unavailable in most settings; thus, diagnosis is clinical until more definitive microbiological testing — such as serology — is resulted. Thrombocytopenia and lymphopenia are common hallmarks of dengue fever; however, neutropenia is a prominent, yet less frequently reported trend. We aimed to identify hematological patterns that can assist frontline clinicians with diagnostic certainty of dengue. Dengue patients presenting to our unit via the Emergency Department were compared to those presenting with other febrile illness (OFI) diagnoses. Patient demographics, day of illness, and neutrophil, lymphocyte, and platelet counts from days 1 to 14 of illness were collected, where available. Analyses were stratified by day of illness. Eighteen patients were included in the dengue group and 151 in the OFI group. The frequency of thrombocytopenia, neutropenia, and lymphopenia was each significantly greater in the dengue cohort than in the OFI group (p < 0.0001). Mean nadir platelet, neutrophil, and lymphocyte counts were significantly lower in the dengue cohort compared to those with OFI (p < 0.001), and the likelihood of a dengue patient having the constellation of thrombocytopenia, neutropenia, and lymphopenia on a single CBC during acute illness was 30-fold higher than in the OFI group (p < 0.0001). As dengue-specific diagnostic testing is often limited by insensitive early serologic diagnostics with prolonged turnaround time, the constellation of thrombocytopenia, neutropenia, and lymphopenia can guide the early diagnostic and treatment approach as well as follow-up of febrile returned travelers with suspected dengue.