It is not always easy to diagnose tuberculosis. Tuberculosis usually causes lungs infection, though not always. TB can cause asymptomatic or silent infection (latent) or active TB that requires diagnosis and treatment. At Bigmanlab our physicians will do a blood tests and skin or physical exam to find out if you have TB. Depending on the results, more tests will be ordered.
In this article, we will discuss about tuberculosis testing and diagnosis at Bigmanlab, how I carry out the different tuberculosis tests and when a TB test needs to be ordered. Also we will look at what test results mean, as well as possible treatments options. This article has been reviewed by Bigmanlab healthcare professionals and is written by myself; head of laboratory procedures at Bigmanlab.
Diagnosis of tuberculosis:
During a physical exam, your doctor use a stethoscope to listen to the sound your lungs make when you breathe after checking for swollen lymph nodes. Although blood tests are becoming more common, the most widely used diagnostic tool for tuberculosis is skin test. Injected just under the skin on the inside of the forearm is a small amount of a substance called tuberculin.
You should only feel a slight prick from the needle. I will then examine your arm Within 48 to 72 hours for swelling at the site of injection. You may have a tuberculosis infection if there’s signs of a red, raised, hard bump. The significance of the test results is determined by the bump size.
Testing for tuberculosis:
Tuberculosis bacteria in the body can be detected by two tests types: the tuberculosis blood test and the TST (tuberculosis skin test). The only significance of a tuberculosis skin test or a positive tuberculosis blood test is that a person has been infected with the tuberculosis bacteria.
Whether the person has progressed to tuberculosis or has latent tuberculosis infection is not specified by this test. Other tests are needed to determine if a person has TB, such as a sputum sample and a chest x-ray.
When should tuberculosis be suspected?
Mycobacterium tuberculosis causes tuberculosis disease. People with these symptoms should be suspected to have tuberculosis:
- Fatigue.
- Loss weight.
- Fever.
- Appetite loss.
- Sweating at night.
If tuberculosis disease occurs in the pulmonary gland (lungs), possible symptoms may be:
- Chest pain
- Cough for more than 3 weeks
- Coughing up blood (hemoptysis)
The symptoms of tuberculosis depend on the area affected if it occurs extrapulmonary (in another body parts).
Depending on the type of TB you suspect, different tests are used to diagnose TB (tuberculosis). I may refer you to one of our tuberculosis specialist for treatment or evaluation if I suspect that you have tuberculosis.
Tuberculosis blood tests:
Interferon-gamma release (IGRA) tests is a blood tests that measures your TB antigens response, things that trigger antibodies production by your immune system. Bigmanlab has two approved tests. In addition to a TB skin test, you can do them instead. You will not need another visit with us once you have a blood test. If you have received the BCG vaccine or have a negative TB skin test then these tests will be helpful.
Tuberculosis infected individuals (with germs) will show a positive tuberculosis blood test result. To see if your tuberculosis is active, I will then conduct more tests on you. I usually draws the patient blood and carry it to a laboratory for reporting after analysis.
Positive tuberculosis blood test:
It entails that tuberculosis bacteria has infected the person. To determine if the person has a tuberculosis disease or latent tuberculosis infection, more tests are needed.
Negative tuberculosis blood test:
This means that tuberculosis disease, latent TB infection is unlikely and that the patient’s blood has not responded to the test.
The TB test of choice is a blood test for:
- Patients having time coming back on a second date for another for a check for a reaction to tuberculosis skin test.
- Patients who have taken the BCG (Bacille Calmette-Guérin) tuberculosis vaccine.
Skin test for tuberculosis:
symptoms are usually absent in many tuberculosis patients. What they have is what’s referred to as latent tuberculosis. The most common way we diagnose tuberculosis at bigmanlab is through tuberculosis skin test, also known as the Mantoux tuberculin skin test.
Just under the skin of the forearm, I will inject a small amount of tuberculin fluid. Inactive tuberculosis proteins are found in this fluid. A small prick can be felt from the needle. I will see if you have a reaction to TST when you return to your doctor in 2-3 days later.
Positive skin tuberculosis test:
This entails the tuberculosis bacteria was detected in the patient. To determine if the person has TB disease or a latent TB infection, more tests are needed.
Negative skin test for tuberculosis:
This entails that it is unlikely that they have an underlying tuberculosis bacterial infection or TB disease because the person's body is not responding to the TB skin test.
Repeating the tuberculosis skin test poses no problem. If it recurs, more tests should be done on a different body part (for example, on the other arm). For children under five years of age, skin test for tuberculosis is the preferred TB test.
Can tuberculosis results go wrong?
Tuberculosis skin test is faulty. It sometimes suggests that that people do not have TB even if they do. It can also prove people have tuberculosis even when they do not. If you have recently been vaccinated with the BCG (Bacille Calmette-Guerin) vaccine, you can get a false positive result.
This TB vaccine is it is widely available in countries with high rates of tuberculosis infection but is rarely used in the west. There can also be possibility of false negative results.
Tuberculosis drug resistance testing:
To ensure your tuberculosis responds to the medicines you are taking, I will first perform drug resistant tests. Otherwise, you may have what is known as drug-resistant tuberculosis. Your TB patient can develop resistance to some of the medicines used to treat tuberculosis when you don't take medicines or miss doses as directed. Medicines may not be unable to fight against the TB disease. You may need more drugs for a longer period of time since drug-resistant TB is more difficult to treat.
What about tuberculosis treatment?
If you are at high risk of developing active TB from latent TB, your healthcare provider may recommend drug treatment. You will need to take antibiotics for at least six to nine months, if you have active tuberculosis. Possible resistance to the drug, general health, your age, and the location of the infection in your body will determine the exact length of treatment and drug.
The most common drug against tuberculosis
You may only need to take one or two types of TB medicine if you have latent tuberculosis. Active TB requires multiple medications at the same time, especially when it is a drug-resistant strain. Common drugs mostly used for tuberculosis treatment are:
- Pyrazinamide
- Isoniazid
- Myambutol (Ethambutol)
- Rifadin, Rimaktan (Rifampicin)
An injectable drug such as Capastat (capreomycin) or amikacin and a combination of antibiotics called fluoroquinolones are usually used for 20-30 months if you have drug-resistant tuberculosis. These drugs are being resisted by some tuberculosis types.
To combat tuberculosis drug resistance, many drugs can equally be added to therapy, for example:
- Zivox (Linezolid)
- Sirturo (Bedaquiline)
A note from Bigmanlab:
It is very important to complete treatment. You may feel better after a few weeks of taking treatment and you will no longer be contagious. Take all your medicines exactly as prescribed by your healthcare provider; you must stop all medicines and do not stop taking your TB medicines. Surviving bacteria become resistant to medicines when treatment is stopped early or doses are missed missing, and this may lead to tuberculosis, which is even much more difficult to cure and dangerous.
