Complete Blood Count (CBC)

What is this test? The complete blood count (CBC) is one of the most common blood tests. It measures the different cells in your blood, including red blood cells, white blood cells, and platelets, and helps your healthcare provider evaluate your overall health.

A sputum culture is a laboratory test that examines a sample of sputum (mucus and saliva that you cough up from your lungs) to identify bacteria that may be causing a respiratory infection such as pneumonia, bronchitis, or tuberculosis. The test uses aerobic culture methods, which means it grows bacteria in the presence of oxygen.

Why is it performed? This test is performed as part of a routine checkup, to look for signs of conditions such as anemia, infection, or blood disorders, and to monitor an existing condition or how well treatments like certain medications are working.

Your doctor may order this test if you have symptoms of a respiratory infection, such as persistent cough, fever, chest pain, or difficulty breathing. The test helps determine the specific bacteria causing your infection, which guides appropriate antibiotic treatment. It is also used to monitor the effectiveness of treatment and to identify antibiotic-resistant bacteria.

How to prepare? Preparation is usually simple and no fasting is required. Drink plenty of water before your appointment, tell your provider about all medicines and supplements you take, and wear a shirt with sleeves that can be rolled up easily above the elbow.

Before the test, do not eat or drink for at least 1-2 hours to reduce contamination from food particles. Rinse your mouth with water to remove debris, but avoid using mouthwash or toothpaste. In the morning is usually the best time to collect the sample, as sputum accumulates overnight. Your healthcare provider will give you specific instructions on how to collect the sample properly.

How is the sample collected? A small blood sample is drawn from a vein, usually on the inside of your elbow or the back of your hand. A technician cleans the site, applies a band, and inserts a thin needle. The collection takes only a few minutes.

You will be asked to cough deeply from your lungs to produce sputum. The sample should be coughed up from deep in your lungs, not just saliva from your mouth. You will typically spit the sputum into a sterile container provided by your healthcare provider. If you cannot produce sputum, your doctor may collect samples using a bronchoscope or other methods.

What do the results mean? Results show whether your red blood cell, white blood cell, and platelet levels fall within the normal range. Abnormal values may suggest infection, anemia, inflammation, or other conditions, and your provider will interpret them together with your symptoms.

A positive result means that bacteria were found in your sputum sample. The laboratory will identify the specific type of bacteria and perform antibiotic sensitivity testing to determine which antibiotics will be most effective. A negative result may indicate that your infection is caused by viruses, fungi, or that the sample was contaminated. Your doctor will interpret the results in combination with your symptoms and other test findings.