Thrombocytopenia in malaria: A red-herring for dengue, delaying the diagnosis of imported malaria

Abstract

Introduction: Fever and thrombocytopenia, often presenting features of malaria, are also the hallmarks of dengue infections. This study examines the degree and duration of thrombocytopenia in imported malaria infections in Sri Lanka and the extent to which this could provide a false trail in favor of a dengue diagnosis. Methods: The data of all confirmed malaria cases reported in Sri Lanka from 2017 to 2019 were extracted from the national malaria database. These included detailed histories, the time to malaria diagnosis, platelet counts, and in 2019, the trail of diagnostic procedures. Results: Over the 3 years, 158 malaria cases (157 imported and one introduced) were reported. Platelet counts were available in 90.5% (n = 143) of patients among whom 86% (n = 123) showed a thrombocytopenia (<150,000 cells/μl) and in nearly a third (n = 52) a severe thrombocytopenia (<50,000 cells/μl). Only 30% of patients (n = 48) were diagnosed with malaria within 3 days of the onset of symptoms, while in 37% (n = 58) it took 7 or more days. Platelet counts where significantly higher in patients who had symptoms for 7 days or more compared to those who had symptoms for <7 days (χ2 = 6.888, P = 0.009). Dengue fever was suspected first in 30% (n = 16) of the total malaria patients reported in 2019. Conclusions: Low platelet counts could delay suspecting and testing for malaria. Eliciting a history of travel to a malaria-endemic country could provide an important and discerning clue to suspect and test for malaria in such patients.

Keywords

• delayed diagnosis
• dengue
• imported malaria
• thrombocytopaenia