Which test can help confirm a diagnosis of Ehrlichiosis?

The confirmation of a diagnosis of Ehrlichiosis can be achieved through a blood smear that demonstrates the presence of morulae within white blood cells (WBCs). Ehrlichiosis is caused by bacteria belonging to the genus Ehrlichia, which infect specific types of white blood cells, particularly monocytes or granulocytes. When a blood sample is taken from an infected individual, examination under the microscope may reveal these characteristic morulae—small, round clusters of the bacteria inside the WBCs.

Although other tests and diagnostic methods may be used in the evaluation of patients suspected of having Ehrlichiosis, they do not provide the direct evidence of infection that a blood smear does. For instance, urinalysis may help identify other co-existing conditions or complications but does not directly confirm the presence of the Ehrlichia bacteria. A skin biopsy is typically unrelated to Ehrlichiosis and would not yield relevant information. Similarly, a chest X-ray would be used to assess respiratory conditions and is not pertinent to confirming an Ehrlichiosis diagnosis.

Thus, the identification of morulae in a blood smear is the most specific and direct method for confirming Ehrlichiosis, making it the most appropriate choice for diagnosis.