Tests and diagnosis

By Mayo Clinic Staff

Tick-borne infections are difficult to diagnose based solely on signs and symptoms because the signs and symptoms, such as fever and muscle aches, are similar to many other common conditions.

Abnormal findings on a number of blood tests, combined with your history of possible exposure, may lead your doctor to suspect a tick-borne illness. If you have ehrlichiosis, your blood tests will likely show:

  • A low white blood cell count — these cells are the body's disease fighters
  • A low platelet count — platelets are essential to blood clotting
  • Abnormal liver function

More specific blood tests for ehrlichiosis include:

  • Polymerase chain reaction (PCR) test. This test helps identify specific genes unique to ehrlichiosis. However, if you've already started treatment, the results of this test may be affected.
  • Indirect fluorescent antibody (IFA) test. This test, not used as commonly as the PCR test, measures the amount of antibody you have in your blood to the bacteria that causes ehrlichiosis.

If you live in an area where ticks are common, your doctor may start you on antibiotics before the results of the blood tests return because earlier treatment results in a better outcome for some tick-borne diseases.

July 11, 2015