Rocky Mountain Spotted Fever (Blood)
Does this test have other names?
RMSF, Rocky Mountain spotted fever antibodies
What is this test?
Rocky Mountain spotted fever serum is a blood test used to look for antibodies, or
proteins, that the body makes to fight Rocky Mountain spotted fever (RMSF) infections.
RMSF is a serious bacterial infection caused by a bite from an infected tick. In most
people, antibodies can't be found until at least a week after infection.
A blood sample is taken about a week after symptoms appear and again 2 to 4 weeks
Why do I need this test?
You may need this test to confirm a diagnosis of RMSF and to see how well treatment
is working. Symptoms of RMSF include:
What other tests might I have along with this test?
Your healthcare provider might order other blood tests. These might include a complete
blood cell count (CBC) and a chemistry panel. A low platelet count, low sodium level,
or higher liver enzymes could mean RMSF. If you have a skin rash, your provider may
order a skin biopsy to look for bacterial infection in the cells that line your blood
What do my test results mean?
Many things may affect your lab test results. These include the method each lab uses
to do the test. Even if your test results are different from the normal value, you
may not have a problem. To learn what the results mean for you, talk with your healthcare
If your first test results are negative, it's still possible you are infected. It's
critical to start treatment right away, so your healthcare provider may suggest treatment
even if your results are negative. He or she will have you repeat the test in a week
Healthcare providers look for a rise in the antibodies. If the second test shows a
significant rise in antibodies, it can confirm that you have RMSF.
The antibodies may stay at higher levels for months or even years after infection.
How is this test done?
The test requires a blood sample, which is drawn through a needle from a vein in your
Does this test pose any risks?
Taking a blood sample with a needle carries risks that include bleeding, infection,
bruising, or feeling dizzy. When the needle pricks your arm, you may feel a slight
stinging sensation or pain. Afterward, the site may be slightly sore.
What might affect my test results?
Antigens may be present in your blood if you have been exposed to related organisms.
Antibiotic treatment also can affect your test results.
How do I get ready for this test?
You don't need to prepare for this test.