Tuberculosis: Diagnosis

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Diagnosis

To diagnose tuberculosis (TB), your health care provider will gather five important pieces of information during the complete history and physical examination:

• Symptoms
• History of exposure
• Tuberculin skin test or blood test for TB
• Chest X-ray or chest CT scan
• Sputum test

You should be tested for TB if:

• You think you might have active TB disease.
• You have spent time with a person you know has active TB disease.
• You are living with HIV, or are otherwise immunocompromised.
• You have lived or were born (and lived for some time) in a community or area where TB is more common. This can include countries in Eastern Europe, Asia, Central and South America, and parts of Asia.  
• You live or work somewhere where active TB disease is more common. In the past, settings such as nursing homes, prisons and shelters for people experiencing homelessness have been impacted by TB. It’s important to contact your local public health department for guidance. 

Tuberculin Skin Test

The tuberculin skin test (TST) uses an extract of dead TB germs used as a purified protein derivative or PPD (Opens in a new window) (Opens in a new window) (Opens in a new window) (Opens in a new window). The dead germs are injected into the skin. If a person has been infected with TB, a lump will form at the site of the injection within 48 to 72 hours. This is a positive test, depending on the size of the lump and other risk factors for TB. This often means that TB germs have infected the body. It does not necessarily mean the person has active disease. People with positive skin tests but without active disease cannot transmit the infection to others.  

If you have been vaccinated for TB with the bacillus Calmette-Guerin (BCG) vaccine, it can create a false positive PPD test. If accessible, we recommend the blood test for TB for people who have been previously vaccinated. The blood test for TB does not have this same risk of a false positive as the tuberculosis skin test. 

Tuberculosis Blood Test

There are two new blood tests that have recently been developed to detect exposure and infection with M. tuberculosis: the QuantiFERON and T-SPOT tests. Both are tests called interferon-gamma release assays or IGRAs. 

Each test involves a blood sample that is then injected with a group of antigens (proteins) found in the bacteria that cause TB. If your immune system has ever encountered these antigens, your cells will produce interferon-gamma, a substance produced by the immune system. The laboratory will measure the amount of interferon-gamma. These tests appear to be more sensitive and specific than the tuberculin skin test. Importantly, unlike the tuberculin skin tests, they are not affected by previous BCG vaccination.

Chest X-Ray

If you have been infected with TB, but active disease has not developed, a chest X-ray will often be normal. Most people with a positive PPD (skin test) or TB blood test have normal chest X-rays and continue to be healthy. For such people, preventive medication may be recommended.

However, if the germ has attacked and caused inflammation in the lungs, an abnormal shadow may be visible on the chest X-ray. In this case, diagnostic tests (sputum tests) and treatment often are appropriate. 

Sputum Test

Sputum is the phlegm or mucus that is coughed up. During a TB sputum test, samples of sputum coughed up from the lungs are tested to see if TB germs are present. The sputum is examined under a microscope (a "sputum smear") to look for evidence of the TB organisms. This is called a sputum smear because the sputum sample is spread thinly across the slide so the laboratory can read through it. 

Because the bacteria that cause TB grow slowly, it can take several weeks to get the results of the tuberculosis sputum test. The results will help your doctor determine which drugs will be most effective in treating your TB. Many strains of the bacteria that cause TB are resistant to one or more drugs used to treat the disease.

If you are unable to cough up sputum, it may be necessary to obtain a specimen by having you inhale a strong saline solution to induce a cough. If that doesn’t work, it may be necessary to obtain a specimen with a bronchoscope or to isolate the bacteria from the stomach or other locations. Very young children and infants with active TB often are not able to produce sputum. Decisions on how to identify and possibly treat TB in children should be done in consultation with a pediatric TB expert. 

CT Chest Scan

A computed tomography (CT or CAT) scan takes many X-ray pictures to build detailed images of the chest. The pictures are more detailed than a typical X-ray. During a CT scan of the chest, pictures are taken of cross sections or slices of the thoracic structures in your body. The thoracic structures include your lungs, heart and the bones around these areas.

For the scan, you remove all clothing and jewelry from the waist up and wear a hospital gown. Avoid having any barium studies done two to three days before a CT scan.

During the CT scan, you will lie on a special table that slides back and forth through a doughnut-shaped ring. The CT technologist will give you instructions during the test like asking you to raise your arms sometimes and to hold your breath for 10 to 12 seconds. While you hold your breath, the table will move through the ring as X-ray images are taken. It is important to lie still. You may be asked to lie on your stomach to have extra pictures taken.

Treatment

Tuberculosis (TB) treatment includes medications and testing to monitor patients’ progress. This includes a practice known as directly observed treatment, in which TB patients are isolated to receive care and report challenges and adverse effects. Directly observed treatment also includes follow-up visits and testing to determine if medications are working or if the disease is progressing.  

One of the biggest challenges with tuberculosis treatment is that the medications can be challenging to take. Treatment regimens often require many pills and can also lead to an upset stomach and other side effects. This can impact a person’s ability to stay on the treatment regimen. If a person isn’t able to take the full treatment regimen or has interruptions in the treatment regimen, this can increase the risk of the TB coming back and never going away. It can also lead to the development of bacterial resistance, when germs develop the ability to overcome the drugs designed to destroy them

Most tuberculosis treatment programs offer support staff to assist patients. This support may include not only addressing treatment side effects, but also any other social or medical challenges that interfere with treatment. Most public health programs offer TB treatment at no cost to patients, including support for monitoring. Some have a patient assistance fund to offset other costs of TB, including taking time off from work due to being isolated or needing to come to medical appointments. If you have TB and are experiencing social or financial stress, talk to your provider about options for support.  

Extrapulmonary TB is active TB disease in any part of the body other than the lungs (for example, the kidney, spine, brain or lymph nodes). Treatment for extrapulmonary disease is basically the same as for TB in the lungs, except that TB involving the brain or bones is treated longer. 

To learn more about how we treat tuberculosis and mycobacterial infections, visit our program page here. 

Active TB Disease Treatment

• Active TB disease is treated with several antibiotics at once to decrease the chances that the bacteria will evolve resistance to the drugs. 
• Active TB disease must be treated aggressively to allow for the best outcomes for an individual and also to decrease spread to others if there is disease in the lungs.
• It is important for patients who are being treated for active to be regularly checked for symptoms and adverse effects. This can include regular follow-up visits and lab work to check your liver or kidney function and regular sputum sampling to determine that the antibiotics are working and ensure bacteria are no longer present. 
• Follow-up chest X-rays may also be recommended to detect signs of advancing disease. 

One out of five patients treated for active TB will experience side effects. The most common side effects are nausea, upset stomach and fatigue. 

In less common cases, some patients will experience liver inflammation, which is why liver tests are often monitored closely while taking tuberculosis treatment. The medication ethambutol can impact visual acuity, so vision also should be monitored monthly when on that drug. The risk of adverse effects may be higher in patients with multiple medical problems, patients who take multiple medications or in patients who are older.  It is important that all TB patients be monitored closely. All medications should be reviewed for possible interactions.

Treatment for Latent TB

• People with latent TB infection (an infection without active disease) have no symptoms.  
• If you have latent TB, you can be around others and do not need to be isolated. 
• Latent TB may be treated with one or two antibiotics for three to nine months. 
• The goal of latent TB treatment is to eliminate TB from your body so that you stay healthy and do not develop active TB.

Patients who are being treated for latent TB also need to be closely monitored for symptoms and adverse effects on the kidneys and liver. Doctors will confirm that the medications are working and watch for signs of advancing disease. This can include follow-up visits, additional lab work, sputum sampling and chest X-rays. 

Common medications used to treat latent TB are rifampin, isoniazid and rifapentine. Learn more about treatments for latent TB on the Centers for Disease Control and Prevention website (Opens in a new window). 

Drug-Resistant Tuberculosis Treatment

• Some people have drug-resistant TB from the start if they were infected by someone whose disease was caused by drug-resistant bacteria. 
• Successful treatment for drug-resistant TB generally requires different medications. 
• Medications for drug-resistant TB often need to be given for a longer period than drug-susceptible TB. 
• Treatment for drug-susceptible latent TB can be as short as one month in some settings, but the usual duration is three to four months. 
• Drug-resistant latent TB treatment is generally six to nine months, but consultation with a TB expert should be done to determine the best approach. 

Drug-resistant TB can be very difficult to treat because:  

• The medication may not work for a particular infection. 
• The patient’s body may not absorb the medication.
• The patient may not be able to follow the treatment plan.
• The patient may experience adverse effects and have trouble with prolonged time in isolation. 

There have been several advances in the treatment of drug-resistant TB since 2020, and now patients who have resistance to rifampin or even all first-line TB treatment medications can be offered a new regimen that may shorten treatment from 18 months to six to nine months. This new regimen is called BPaLM or bedaquiline, pretomanid, linezolid, and moxifloxacin. 

If patients cannot take moxifloxacin or have resistance to medications in that drug class they can still take BPaL. Both regimens can cure drug-resistant TB in six to nine months in most adults.  

Tuberculosis Treatment in People Living with HIV

• Tuberculosis is the leading cause of death among people living with HIV in areas where TB is prevalent. 
• Many people living in communities and countries impacted by TB also experience similar challenges in accessing health care. 
• Lack of access to appropriate treatment for HIV often is associated with the progression of HIV and profound immunosuppression. 

When people become immunocompromised, the risk of acquiring TB infection and progressing to having active TB can increase. Treating both HIV and TB can be complex, but with growing treatment options, people with HIV and TB are experiencing better outcomes. 

Tuberculosis Prevention

The main way to avoid infection with the bacteria that cause TB is to avoid exposure to people with active disease. However, sometimes this isn’t practical because many people with active TB are not aware that they have it. Primary caregivers for TB patients often cannot avoid exposure.  There is no vaccine that eliminates the risk of TB infection. However, there is a vaccine that is offered to children that can reduce the risk of the most severe forms of TB, such as TB meningitis. The bacillus Calmette-Guerin (BCG) vaccine is often administered to infants and small children in countries where TB is common. BCG is not offered in the United States.   

Many people who receive the BCG vaccination will have a positive TB skin test for the rest of their lives but can be tested accurately for TB infection with the blood test for TB or an interferon gamma release test, such as QuantiFERON or T-SPOT.

When you know you’ve recently been in close contact with someone with active tuberculosis and you have had a positive tuberculin skin test or TB blood test, preventive treatment is recommended. The risk of developing active TB after having TB infection is higher during the first two years after exposure. Taking a preventative treatment medication is important to reduce the risk of developing active TB.  

Lifestyle Management

People with active TB disease should isolate until they: 

• Are on treatment. 
• Show signs of improvement. 
• Complete the recommended duration of isolation. 

For patients living alone, public health programs can offer support services for safer isolation. If patients experience financial or other social difficulties while in isolation, some public health programs can offer additional support.

If you are being treated at home at the beginning of active TB disease treatment, while you are still in isolation, it is important to try to limit exposure to others. However, once you start treatment, the risk of exposing others decreases substantially. For patients who are not able to isolate from family members (caregivers of infants or young children, people who are breastfeeding) public health will rapidly evaluate those at risk. For children under the age of five, “window” or prophylactic treatment is often offered. 

Previously, public health officials recommended separation of family members who were ill. However, a more pragmatic approach is to try to keep a household together and rapidly offer services to all household members. Family members or close friends who do not live in the household should defer their visits until the isolation period has ended. 

If you do have active TB and have just started treatment, you can also take additional precautions such as:

• Wear a surgical mask to cover your nose and mouth. 
• Cover your mouth with a tissue when coughing and sneezing. Then, seal the tissue in a bag to throw it away. 
• Make sure your rooms have adequate ventilation, so that any bacteria you exhale are carried away. You can place a fan facing out of a window to blow bacteria-laden air out of the room. 

People with active TB in their lungs will be discreetly asked by public health staff to share the identifying information of people who were in close contact with them. While this can feel very challenging and create additional stress, it is important to ensure that people who are exposed have access to TB prevention services. Public health staff are very careful not to reveal the identity of the individual with TB when contacting people who may have been exposed, especially when the exposure happens in a public setting (such as a school or workplace).    

If you have active TB, taking all of your treatment is important. If you face difficulties in taking medications, either because of side effects, social challenges or other factors, it is important to share this with either your provider, the outreach staff or other healthcare professional you trust. There are support services in many public health programs. You have a right to access these services if eligible, even if you are in isolation.   

See a Specialist 

Proper TB treatment requires expert care. With over a century of experience specializing in TB, National Jewish Health is uniquely positioned to help with your case. Learn more about how our team at the Division of Mycobacterial & Respiratory Infections can get you on the right track.