Eve B. Hoover is completing a postgraduate academic fellowship at Midwestern University at Glendale, Arizona, and practices at Logistics Health, Inc, in Phoenix. The author has no significant financial relationships to disclose.
Differentiating between dengue, malaria, and chikungunya early in presentation Hematologic parameters can be used as a diagnostic aid when differentiating among certain causes of fever, as noted in a study by Joshi and Shah.22 In the setting of a febrile illness, thrombocytopenia (platelet count < 150,000/µL) is a predictor of malaria, especially in combination with anemia (hemoglobin < 10 g/dL). Thrombocytopenia is also common with dengue fever, but patients with dengue typically have normal hemoglobin. According to Joshi and Shah, patients having the combination of anemia and thrombocytopenia were 22 times more likely to have malaria than patients without these laboratory findings.22
Kutsuna and colleagues also found disease-specific clues in laboratory data when differentiating between dengue fever and malaria. Patients with dengue fever had significantly lower white blood cell counts than patients with malaria.23 In addition, although thrombocytopenia is seen in both dengue fever and malaria, platelet counts are lower in patients with malaria at first presentation. However, with dengue fever the platelet count can decrease three to six days into the illness when fever abates.23 Furthermore, total bilirubin tends to increase in malaria but is unaffected in dengue fever. Last, C-reactive protein can be helpful in assessing malaria severity and clinical improvement at follow-up, as well as for differentiating malaria from other conditions (eg, dengue), especially if the value is greater than 10 mg/L.23
Distinguishing chikungunya from dengue fever in the early stages of illness is difficult, and there is no pathognomonic hematologic laboratory study that helps with this task. With both diseases, the patient may have leukopenia, elevated erythrocyte sedimentation rate, and (rarely) thrombocytopenia. Chipwaza and colleagues discuss the significant overlap in symptoms in nonmalaria febrile illness. The overlap makes clinical diagnosis difficult; lab testing is essential for establishing the diagnosis.21 Once CHIKV is confirmed, the clinician is typically reassured of a more benign, self-limited course.
