Complete Blood Count (CBC) Test: What It Measures, Why Your Doctor Orders It, and How to Understand Your Results

What is this test? A complete blood count, or CBC, is a routine blood test that measures the different cells circulating in your blood, including red blood cells, white blood cells, and platelets. Because these cells carry oxygen, fight infection, and help your blood clot properly, counting them gives your care team a broad picture of your overall health.

The Borrelia burgdorferi IgA Antibody test is a blood test that looks for IgA antibodies in your serum. IgA antibodies are one of the first types of antibodies your immune system produces when exposed to the Borrelia burgdorferi bacteria, which causes Lyme disease. This test helps healthcare providers determine if you have been infected with Lyme disease bacteria.

Why is this test performed? Doctors order a CBC for many reasons: as part of a routine checkup, to investigate symptoms such as fatigue, weakness, fever, bruising, or unusual bleeding, to help detect conditions like anemia, infection, or blood disorders, and to monitor how an ongoing condition or a treatment you are receiving is affecting your blood cells over time.

This test is primarily used to help diagnose Lyme disease. It may be ordered when a patient has symptoms suggestive of Lyme disease, such as the characteristic bull's-eye rash (erythema migrans), fever, headache, fatigue, or joint pain. It is particularly useful in the early stages of infection when IgA antibodies may be present before other antibody types. Your healthcare provider may also order this test if you have a history of potential tick exposure and are experiencing related symptoms.

How is the test done? A small sample of blood is drawn from a vein, usually on the inside of your elbow or the back of your hand. A healthcare professional cleans the site, wraps an elastic band around your upper arm, collects the blood into a tube using a thin needle, and then removes the band and needle. The procedure takes only a few minutes.

A healthcare professional will draw a small sample of blood from a vein in your arm. This blood sample will be sent to a laboratory where technicians will analyze it for the presence of IgA antibodies against Borrelia burgdorferi. The test does not require fasting, and you can resume your normal activities immediately after the blood draw. The sample is then processed using specialized laboratory techniques to detect the antibodies.

Understanding your results: Your report lists each blood cell type alongside a reference range showing the values considered normal for healthy adults. Values slightly outside the range are common and do not always mean illness, but results that are clearly high or low may point to conditions such as anemia, infection, inflammation, or clotting problems. Always review your results with your healthcare provider, who can interpret them together with your symptoms, medical history, and other test findings.

Test results are typically reported as positive or negative. A positive result means that IgA antibodies to Borrelia burgdorferi were detected in your blood, suggesting you have been exposed to the Lyme disease bacteria. A negative result means no IgA antibodies were detected. However, it is important to note that false negatives can occur, especially in very early infection before antibodies have developed, or if the infection is very recent. Your healthcare provider will interpret your results in context with your symptoms, medical history, and potentially other test results.