What is the blood test for bacterial infection?
A blood test to detect bacterial infection isn't a single test, but rather involves several different methods. These tests look for indicators of infection in the blood, such as the presence of bacteria itself or substances the body produces in response to an infection.
- Blood Culture: This is the most direct way to identify a bacterial infection. A sample of blood is collected and cultured in a lab to allow bacteria to grow, if present. This test identifies the type of bacteria, guiding treatment decisions. MedlinePlus and Cleveland Clinic both describe this as a primary method for detecting bacterial infections in various bodily fluids, including blood. Testing.com also details the procedure and its purpose.
- Complete Blood Count (CBC): A CBC doesn't directly detect bacteria, but it measures various blood components, including white blood cells. Elevated white blood cell counts, particularly neutrophils and bands (immature neutrophils), often suggest a bacterial infection. While not definitive, this is a helpful indicator. University Hospitals highlights the use of a CBC in distinguishing between bacterial and viral infections. Verywell Health mentions increased white blood cells as a common sign of bacterial infection.
- Procalcitonin (PCT): This blood test measures procalcitonin, a protein that rises in response to bacterial infections (but not viral infections). PCT levels can help differentiate between bacterial and other types of infections. Sepsis Alliance specifically mentions procalcitonin as a marker for bacterial infections.
New Developments
Researchers are constantly developing new and improved blood tests for infections. For example, a Stanford Medicine study describes a new test with 90% accuracy in differentiating between bacterial and viral infections. Stanford Medicine
Important Note: These tests are used in conjunction with a patient's clinical presentation and other diagnostic tests. A doctor interprets the results to arrive at a diagnosis and determine the best course of treatment.
