Complete Blood Count (CBC): A Common Blood Test That Measures Your Red Blood Cells, White Blood Cells, Platelets, and Hemoglobin

A complete blood count (CBC) is one of the most frequently ordered blood tests. It measures the cells circulating in your blood, including red blood cells, white blood cells, and platelets, along with hemoglobin and hematocrit, which reflect your blood's ability to carry oxygen. This quick test gives your doctor a broad picture of your overall health.

This molecular test looks for a specific gene called blaCMY-2 in bacteria. This gene produces an enzyme called AmpC beta-lactamase, which can break down and destroy certain antibiotics called beta-lactam antibiotics (including penicillins and some cephalosporins). When this gene is present, the bacteria become resistant to these important drugs, making infections harder to treat.

Your doctor may order a CBC as part of a routine health exam, to help find the cause of symptoms such as fatigue, weakness, fever, unexplained bruising, or bleeding, to monitor a condition like anemia or infection, or to check how treatments such as chemotherapy or certain medications are affecting your blood cells over time.

Your doctor may order this test if you have a bacterial infection that is not responding to standard antibiotic treatment. It helps determine whether antibiotic-resistant bacteria are causing your illness, which allows your doctor to select more effective medications. This is especially important for serious infections like bloodstream infections, urinary tract infections, or abdominal infections.

The test is performed with a simple blood draw, usually from a vein in your arm. A healthcare professional will clean the site with an antiseptic, place a band around your upper arm, insert a small needle, and collect a sample into a tube. The sample is then sent to a laboratory, and results are typically available within a day or two.

A blood sample is drawn from a vein in your arm. The sample is then sent to a laboratory where specialized technicians use molecular techniques (such as PCR - polymerase chain reaction) to detect the presence of the blaCMY-2 gene. The test does not measure how well antibiotics work, but rather identifies the genetic material that causes resistance.

Abnormal results can point to many different conditions. Low red blood cell counts or hemoglobin may suggest anemia, while a high white blood cell count can indicate infection or inflammation. Unusual platelet levels may affect how your blood clots. Your doctor will interpret your values alongside your symptoms, exam findings, and medical history.

The test result will be either 'Detected' or 'Not Detected'. If 'Detected' is reported, it means the bacteria causing your infection carry the blaCMY-2 gene and are likely resistant to certain beta-lactam antibiotics. If 'Not Detected' is reported, the specific resistance gene was not found. Your doctor will use this information along with other test results to determine the most appropriate treatment plan for you.