A chest X-ray can usually detect active tuberculosis (TB) but not latent TB. In either case, you’ll need a sputum test to confirm a diagnosis.

Doctors often use chest X-rays to help diagnose active tuberculosis (TB).

TB is a serious bacterial infection of Mycobacterium tuberculosis in the respiratory tract that can cause many severe symptoms like:

  • a long lasting cough
  • coughing up blood
  • fever
  • chills

As TB bacteria grow and spread, they can cause noticeably dense, white spots on areas of your chest X-rays that are typically clear or translucent.

Read on to learn more about how and why doctors use chest X-rays to help diagnose TB.

X-rays are one of several tests doctors use to detect and diagnose TB, depending on whether you have an active or latent (inactive) TB infection.

Active TB infection

Using a few different tests together, such as a skin test, blood test, and chest X-ray, can help a doctor detect a TB infection.

If you have TB symptoms or a positive skin or blood test indicating a TB infection, you’ll get a chest X-ray that can help a doctor find areas in your lungs where TB bacteria are growing.

Areas of TB bacterial infection can cause white spots called nodules or masses to appear in your lungs on X-ray images, especially near the top of one or both lungs.

Latent TB infection

In its early stages or when it’s latent, TB can be difficult to detect on a chest X-ray.

Even if nothing remarkable appears on your X-ray and you have no symptoms, you may still have TB bacteria in your body. Only a skin or blood test can detect it.

A doctor might ask you to take several X-rays over a specific period to watch for any new nodules.

Research suggests that chest X-rays can be helpful tools in detecting pulmonary TB.

According to 2021 World Health Organization guidelines, chest X-rays have a sensitivity of 85–95%, which is how often a positive test result is accurate. They also have a specificity of 89–96%, which is how often a negative test result is accurate.

Doctors may use skin and blood tests to identify a TB infection in people without symptoms. But these can sometimes result in false positives, especially if you’ve recently gotten a TB vaccine. X-ray images can provide a clearer image of what’s going on in your lungs and where a TB infection might be present.

Still, a chest X-ray isn’t enough to confirm a TB diagnosis. Other conditions may cause similar X-ray findings. You’ll need further tests to confirm the presence of TB bacteria.

Other tests for tuberculosis

Doctors may use the following tests to confirm the presence of TB bacteria:

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Chest X-ray findings can help a doctor find nodules, masses, or lesions that indicate colonies of TB bacteria and damage to tissues from infectious bacteria. These usually show up as brighter patches of white on your lungs.

X-rays can also help show the size, shape, and density of a TB infection. The denser the area of white, the more advanced a TB infection usually is.

A doctor may also be able to detect swollen hilar lymph nodes. These are lymph nodes near your hilum, the wedge-shaped area in the middle of your lung.

Multiple small nodules can indicate miliary TB, a very severe form of TB in which the infection has spread to other organs.

TB can also reveal complications like pleural effusion, which is a buildup of fluid around your lungs.

The procedure for a chest X-ray for TB typically follows these steps:

  1. You’ll enter a room with a camera on a large metal arm. Medical staff will position you next to a plate that helps capture X-ray images.
  2. You’ll put on an apron made of lead to protect you from potentially harmful radiation.
  3. You’ll stand still and hold your breath while radiation passes through the plate to capture images.

A chest X-ray usually takes about 20 minutes to complete.

Here are some of the most frequently asked questions about how chest X-rays help with TB diagnosis.

How does tuberculosis differ from pneumonia on a chest X-ray?

TB usually shows up as a series of spots or lesions that indicate damage to tissues affected by TB infections. Pneumonia may show up as small white areas or appear throughout both lungs.

TB infections also tend to start in the top of your lungs, but there’s not a specific pattern that happens with TB infections. Pneumonia can appear almost anywhere in your lungs, but it’s more likely to appear in the bottom of the lungs.

How many chest X-ray views do you need to rule out TB?

The most common chest X-ray view is the posterior-anterior view, which shows your chest from the front and back.

This is usually enough for a doctor to identify TB on an X-ray. Still, they may also request a lateral X-ray, which shows your chest from the side, to help confirm a diagnosis.

Is a chest X-ray enough to diagnose TB?

While chest X-rays can be helpful in screening for active TB, they’re not enough to confirm a diagnosis. You’ll need a sputum test to confirm TB.

Latent or early TB infections might not show up on an X-ray or be hard to spot. Doctors will also use other tests to check for TB in these cases.

What other imaging techniques can doctors use to diagnose TB?

Doctors can learn about TB through other imaging techniques, like ultrasound, MRI, or CT scans. But X-rays are typically more readily available and cheaper.

A chest X-ray is one tool that can help detect TB. Doctors can use X-ray findings along with the results of a skin or blood test to check for a TB infection. However, a sputum test is necessary for an accurate diagnosis.

Talk with a doctor if you’re concerned about a TB infection, especially if you have symptoms.