How Is Rocky Mountain Spotted Fever Diagnosed?

The diagnosis of RMSF is usually made clinically when a patient's history of their problem includes a fever and a rash (usually on the wrists and ankles first, then to the palms and soles of the feet) that occurs a few days after a tick bite. Treatment should not be delayed while waiting for a definitive diagnosis as the disease may advance rapidly. A laboratory test is done in some patients with a presumptive diagnosis of RMSF. It is a biopsy of the skin rash stained specifically to show R. rickettsii in the patient's cells. Another test involves a direct immunofluoresence staining ofR. rickettsii in skin-tissue samples; such tests can confirm the diagnosis in about 70% of cases and, in some laboratories, can be done the same day the specimen is collected.