A blood culture test is a test that analyzes the blood for foreign bodies such as yeast, bacteria, and other microorganisms. The presence of these disease causing agents in the bloodstream may be a sign of an infection of the blood, a condition called bacteremia. Testing positive for blood culture means you have a pathogen like bacteria in your blood.
Infections like this tend to affects the blood that circulates throughout the body. The common sources of blood infections are bacteria from the digestive tract, urine, lungs, or skin.
If an infection is severe or if the immune system cannot contain it, it may become systemic by spreading to your blood. Sepsis is the term given to a systemic bacterial infection.
A blood culture test requires a simple blood sample. Big Man Lab will analyze the blood sample and send the results to your health care provider, who can use them to determine what is needed to treat your infection.
Purpose of blood culture test
If your doctor suspects you may have a blood infection, a blood culture is done. Blood infections can cause serious complications so it is essential to test for blood infections. Sepsis is an example of the complications of blood infection.
In sepsis, the disease causing agent in the bloodstream that causes an infection may disrupt the body's normal defenses and prevent proper functioning of the immune system. Disease causing agent may equally produce organ damaging toxins.
Using the blood culture test results, your health care provider can determine what specific bacteria or organism is causing the infection in your blood and how best to treat it.
What does blood culture test measure?
Blood culture tests analyzes and measures the growth of germs that can result to blood infections, such as fungi or bacteria. To investigate if the infection is caused by a virus, Big Man Lab technicians use special tests for this purpose.
To carry out the blood culture test, a Big Man Lab technician places a portion of your blood sample in a petri dish that contains a substance that stimulates the growth of germs or bacteria. This substance is called culture. To determine if germs can be detected, the petri dish is then observed for weeks or days. Big Man Lab can also watch how fast and how much bacteria (germs) grow.
Further testing is done to identify the bacteria if they are detected in the blood culture test dish. This may require examining the bacteria or germs under a microscope while using chemical stains, for instance Gram stain, to identify fungi or bacteria. Big Man laboratory equally uses other methods, including molecular tests that use PCR (polymerase chain reaction) techniques, to identify some types of blood germs.
Drug susceptibility testing is often used with blood culture tests. Drug susceptibility testing involves adding one or more antibiotics to a culture section to see how effectively they kill blood germs. This test type can help your health care provider to choose the most effective treatment for your infection.
Why take a blood culture test?
If your health care provider orders this test, it is because wants to test your blood for certain types of germs, as he thinks you may have a systemic infection. Results of the blood culture test can help your doctor find the most effective treatment for you.
If you have the following symptoms, your doctor may order tests:
- Nauseating
- Confusion
- Faster breathing or heartbeat
- Chills or fever
- Fatigue
- Urinate less frequently than usual.
You may be experiencing the following if the infection is more severe:
- Severe drop in blood pressure.
- Organ failure
- Inflammation in various areas of the body.
- Small blood clots form in small blood vessels.
Performing a blood culture test
At Big Man Lab, at least two blood samples from different veins are required for a blood culture test. More samples are used as this provides more reliable blood culture test results. Big Man Lab may sometimes collect 3 or 4 blood samples of your blood.
Blood collection can be done in a variety of healthcare settings, such as the laboratory, doctor's office, or even the hospital. Emergency room blood collection is done for patients showing severe symptoms of blood infection.
Before the blood culture test
A blood culture test usually requires no preparation before it is performed. However, because antibiotic medications can affect test results, testing is often done before starting antibiotic treatment. If you have taken antibiotics prior to the blood culture test, you should inform your doctor.
During the blood culture test
Two to four different blood samples are normally taken for a blood culture testing. Two initial samples and an additional sample of your blood may be taken several hours later or samples may be taken all at once.
Blood samples are often taken from a vein in your arm. To increase blood flow in your veins, each time blood is drawn, the lab technician will tie an elastic band around your arm. Using an antiseptic, your skin is then thoroughly cleansed. This is an essential step to ensure that the blood sample is not contaminated with skin bacteria.
A brief burning sensation will be felt when a needle is inserted through the skin into your vein. The blood is placed in a vial and once sufficient blood has been collected, the needle is removed. For each blood sample requested, the same process is repeated. Each blood draw often takes less than a few minutes.
After the blood culture test
A gauze or bandage is often applied to the area where the blood was drawn. You may experience pain or bruising at the injection site, but this often goes away rapidly.
Serious complications resulting from blood sampling are rare. However, be sure to tell your health care provider if you later experience serious or persistent side effects.
Risk associated to blood culture test
The risk of taking blood samples is low. The size of arteries and veins varies from individual to another and from one body side to the other. Some people may find it more difficult than others to have blood drawn.
Other blood collection risks are minor, but may include:
- Several punctures to find the vein.
- Accumulation (of blood under the skin Hematoma)
- Infection (reduced risk of skin damage)
- Heavy bleeding
- Fainting or dizziness
Results of blood culture tests
Availability of blood culture test results
It may take anywhere from a few days to several weeks to receive blood culture test results.
Germs or pathogens must have time to multiply in the laboratory. The time needed may depend on the particular type of germ/pathogen that is believed to be causing the infection. In most cases, the initial blood culture test can be ready within five days, but for some diseases like as tuberculosis, testing can continue for up to a month.
At Big Man Lab, after the test is completed, your doctor will usually give you the results in person or by phone call. Big Man Lab equally provides you with your reports for viewing through the online health portal bigmanlab.com.
Interpret blood culture test results
Blood culture test results depend on whether germs are detected. The blood culture test report may indicate that the blood culture test is positive or negative.
- A negative blood culture test result means that no pathogen or germs are growing in the culture.
- A positive blood culture test result means that one or more pathogen have grown in the petri dish. A positive blood culture test result indicates the presence of pathogen in the blood.
It is possible that some samples may be negative and others may be positive, because blood culture involves several test samples.
Blood is normally sterile, meaning there should be no bacteria, viruses, or fungi. Therefore, a positive blood culture test result may be a sign of infection. If your test result is positive, your test report may include additional information, including:
- The speed at which the pathogen grow.
- How many pathogens grow in a certain period of time?
- How many and which samples tested positive?
- The specific germ type present.
Each one of the factors is essential when interpreting your blood culture test results. Some types of pathogens are almost always linked with potentially severe infections. Other pathogens can develop due to contamination of laboratory equipment or samples and not due to a blood infection.
Therefore, if your blood culture test result is positive, details should be reviewed by your health care provider, who can evaluate how the test result affects your general health, your symptoms, and the results of other blood tests.
Your blood culture test report may also contain information about drug sensitivity testing, if harmful germs can be detected during the blood culture test. This details can help your health care provider choose the most effective treatment for your infection.
Are blood culture test results correct?
Culture tests are widely considered the ideal method for identifying germs that cause infections and are extremely accurate. However, no test is ideal, and blood culture test results can be affected by a couple of factors:
Germs that don’t grow in laboratory cultures: Some types of viruses, fungi, and bacteria are impossible or difficult to grow in a laboratory. An individual infected with one of these pathogens can test negative even if they have the infection.
Contamination of samples: Sometimes germs from lab equipment enter the culture petri dish or germs from the skin enter the blood when blood is drawn. In this case, even if the germs are not present in the blood, the blood culture test result may be positive. This is referred to as a false positive result. Doctors carefully interpret positive blood culture test results to find out when contamination could affect test results and healthcare providers take steps to reduce the contamination risk.
Antibiotic use: The accuracy of your blood culture test may be affected if you have started taking antibiotics or any other antimicrobial medications. Therefore, before starting treatment of the infection, samples for blood tests are usually collected.
Conflicting blood test results: At times, lab equipment find germs in a blood culture test, but closer examination with a microscope or other methods does not detect any germs. Inconsistent results like this are rare, but if they occur, the blood culture test may need to be repeated.
Blood culture test results are generally reliable and are often used in the treatment of infected patients. You can talk to your health care provider for more details if you have questions about the test accuracy.
Message from BigManLab:
Some types of yeast and bacteria are difficult to grow in culture, so you may require a special culture. Furthermore, this culture is unable to detect viruses. Therefore, further testing may be necessary if you have a viral infection.
