Complete Blood Count (CBC) with Differential: A Common Blood Test to Check Your Overall Health

A complete blood count, or CBC, is a routine blood test that measures the different cells in your blood, including red blood cells, white blood cells, and platelets. It gives your doctor a broad picture of your overall health and can help detect a wide range of conditions.

The Rickettsia rickettsii IgG and IgM panel is a blood test that detects antibodies your immune system produces in response to Rickettsia rickettsii bacteria. This bacteria causes Rocky Mountain spotted fever (RMSF), a serious tick-borne disease. The test measures two types of antibodies: IgM (which appear early in infection) and IgG (which develop later and provide long-term immunity).

You may need this test as part of a routine checkup, to investigate symptoms such as fatigue, weakness, fever, bruising, or unusual bleeding, or to monitor an existing condition like anemia, infection, or a blood disorder. It is also used to track how well certain treatments are working.

Your healthcare provider may order this test if you have symptoms of Rocky Mountain spotted fever, especially if you live in or have recently visited areas where tick bites are common. Early symptoms include fever, headache, rash (typically appearing 2-4 days after the tick bite), and muscle pain. Early diagnosis is crucial because RMSF can progress rapidly and become life-threatening if not treated promptly with antibiotics.

The test is performed with a simple blood draw. A healthcare provider will clean your skin, wrap a band around your upper arm, and use a small needle to collect a sample of blood from a vein, usually in your arm. The whole process takes only a few minutes, and you can return to normal activities right afterward.

A healthcare professional will draw a small blood sample from a vein in your arm. The blood will be sent to a laboratory where technicians will analyze it for the presence of IgG and IgM antibodies against Rickettsia rickettsii. The test requires no special preparation, but it's important to tell your doctor about any recent infections or tick exposures.

Your results will show whether your blood cell counts fall within the normal reference ranges. Values that are too high or too low may point to conditions such as anemia, infection, inflammation, or clotting problems. Keep in mind that abnormal results do not always mean a serious problem, and your doctor will explain what your numbers mean and whether any follow-up testing is needed.

Results are typically reported as positive or negative for IgG and IgM antibodies. A positive IgM result usually indicates a recent infection (within the past 1-2 weeks). A positive IgG result may indicate a past infection or one that occurred several weeks ago. Your doctor will interpret these results alongside your symptoms, medical history, and the timing of your potential tick exposure. In some cases, repeat testing may be needed to confirm the diagnosis.