If you smoke or have a significant smoking history, your doctor may have recommended a low-dose CT lung scan to screen for lung cancer before symptoms appear. A radiologist reviews your scan and assigns a Lung-RADS score, a standardized rating system that helps your care team communicate the level of concern around any findings in your lungs and which follow-up steps, if any, are recommended.
Because a low-dose CT can detect nodules as small as a grain of rice, this screening gives your doctor a much clearer picture of your lung health than a standard chest X-ray. In this guide, you’ll learn what each Lung-RADS category means, why the system exists and how it helps your care team make informed decisions about your health.
What Is Lung Cancer Screening?
Lung cancer screening is a preventive exam that uses a low-dose CT lung scan to create detailed pictures of your lungs using a small amount of radiation. This quick, non-invasive scan is designed to find lung cancer at its earliest and most treatable stage, often before you notice any symptoms at all. Unlike a standard chest X-ray, a low-dose CT can detect nodules as small as a grain of rice, giving your doctor a much clearer picture of your lung health.
Medicare recommends that adults aged 50 to 77 who have a significant smoking history should get lung cancer screening. This includes people who currently smoke or who quit within the past 15 years.
A low-dose CT lung scan is specifically for people without active lung symptoms. If you’re experiencing a persistent cough, chest pain or shortness of breath, your doctor may recommend a chest CT scan to diagnose your lung symptoms.
What Is a Lung-RADS Score?
After your low-dose CT lung scan is complete, a board-certified radiologist reviews your images and assigns a Lung-RADS score. Lung-RADS stands for “Lung Imaging Reporting and Data System.” It’s a standardized classification developed to help radiologists and doctors communicate screening results clearly and consistently.
Instead of writing lengthy descriptions for each result, radiologists use a numbered category from 0 to 4, sometimes with a letter added, to summarize what they found on your scan. Your doctor then uses that category to guide your care. Depending on your result, you may be asked to come back for another screening in 12 months, return sooner for a follow-up low-dose CT scan or have additional testing to take a closer look.
The Lung-RADS system removes guesswork from your care and gives your doctor a consistent, evidence-based framework to act on your results.
What Do the Lung-RADS Score Categories Mean?
Each Lung-RADS category reflects a different level of concern and points to a recommended next step. Understanding what your category means can help you feel prepared and confident when you and your doctor talk through your results.
Lung-RADS 0: More Information Is Needed
A Lung-RADS category 0 result is called “incomplete.” This doesn’t mean the radiologist found something concerning. It means the radiologist needs additional information before assigning a final score.
You may receive a category 0 if:
- Prior scans from another facility weren’t available for comparison
- The images didn’t fully capture both lungs
- A finding appears to be related to an infection or inflammation that should settle before you’re reevaluated
In most cases, a Lung-RADS category 0 result means you’ll repeat the scan in one to three months so the radiologist can assign a more definitive score.
Lung-RADS 1: No Suspicious Findings
A Lung-RADS category 1 result is a negative result. No concerning lung nodules were found during your scan. This is the clearest result a screening can produce.
With a category 1 result, your doctor will typically recommend another low-dose lung CT scan in 12 months. No additional testing or follow-up imaging is usually needed before then.
Lung-RADS 2: Benign or Very Low Concern Findings
A Lung-RADS category 2 result means the radiologist saw a nodule or other lung finding, but it has the appearance of something benign, or non-cancerous. This could be a small nodule that falls below the Lung-RADS cutoff for closer follow-up, a nodule with features that strongly suggest it’s not cancerous or a nodule that has remained stable across prior scans.
The estimated chance of malignancy with a category 2 result is less than 1%. Just like a category 1 result, the recommendation is to continue with your annual screening. No additional testing is needed between now and your next yearly scan.
Lung-RADS 3: Probably Benign, But Follow-Up Is Needed
A Lung-RADS category 3 result means the radiologist found something that is probably benign but warrants a closer look over the coming months. The estimated chance of malignancy is between 1% and 2%, which remains very low. However, the nodule has certain features that make it worth confirming through continued monitoring.
With a category 3 result, your doctor will typically recommend a follow-up low-dose CT scan in six months. This is a proactive step, not a cause for alarm. It gives your care team the chance to confirm that the nodule is stable or decreasing over time. If it stays the same or decreases, the radiologist may downgrade the Lung-RADS category score at your next scan.
Lung-RADS 4A: Suspicious Finding That Needs Closer Follow-Up
A Lung-RADS category 4A result means the radiologist saw a nodule or other lung finding that needs closer follow-up. The estimated chance of malignancy is between 5% and 15%.
Your doctor will typically recommend a follow-up low-dose CT scan in three months. In some cases, if the solid portion of a nodule is large enough, your doctor may request a PET-CT scan to gather more information. Additional imaging can help your care team see whether the nodule is stable, shrinking or growing, and whether additional testing is needed.
A category 4A result is not a diagnosis. It means the nodule needs closer follow-up so your care team can watch for changes and decide whether additional testing is needed.
Lung-RADS 4B: Very Suspicious Finding
A Lung-RADS category 4B result means the nodule has features that need more careful evaluation. The estimated chance of malignancy is greater than 15%, but this result is still not a cancer diagnosis. Nodules in this category are often larger, growing or have characteristics that call for a closer look.
Your doctor may recommend a chest CT with or without contrast, a PET-CT scan or a biopsy, depending on the size and appearance of the nodule. While a 4B result can feel stressful, the goal of follow-up testing is to get clearer answers. This next step helps your doctor learn more about the nodule and decide how to move forward with your care.
Lung-RADS 4X: Suspicious Finding With Concerning Features
A Lung-RADS category 4X result is assigned when a category 3 or 4 nodule has additional features that your care team wants to evaluate more closely. These features may include:
- Spiculation, which means the edges of the nodule look uneven or have fine lines extending outward
- A ground-glass nodule, or a hazy-looking spot on a CT scan, that has grown over time
- Enlarged lymph nodes in the surrounding area
A 4X score usually leads to a more detailed evaluation. Depending on the findings and your health history, your doctor may recommend:
- A chest CT
- A PET-CT scan
- A biopsy
This follow-up is designed to give you and your doctor clearer information. Your care team will review the full picture, explain what they see and help you understand the next step that makes the most sense for your situation.
Lung-RADS S: A Significant Finding Not Related to Lung Cancer
Sometimes a low-dose lung CT scan shows something important outside of the lung cancer screening itself. When that happens, the letter “S” may be added to your Lung-RADS score, such as 2S or 3S. The “S” stands for a “significant finding.” These are also called “incidental findings,” which means the scan picked up something extra while looking at your lungs.
Examples of significant findings include:
- Coronary Artery Calcification: This means there are signs of calcium or plaque buildup in the blood vessels that supply your heart.
- Emphysema: This is a lung condition often linked to smoking that can make it harder to breathe over time.
- Aortic Aneurysm: This means part of the body’s main blood vessel, called the aorta, looks wider than expected.
Your doctor can explain what the finding means and whether any follow-up is needed.
Can a Lung-RADS Score Change Over Time?
Your Lung-RADS score isn’t permanent. It reflects what the radiologist sees at a single point in time and can change with every scan.
A nodule that earns a category 3 at your first screening may be reclassified as a category 2 at your six-month follow-up if it has stayed the same size or decreased. On the other hand, a nodule previously classified as category 2 could be upgraded if it has grown or developed features that need closer follow-up.
This is one of the most important reasons regular screening and timely follow-up imaging matter. Comparing scans over time helps doctors tell the difference between nodules that appear stable and those that need more attention. If you’ve had imaging done at another facility, sharing those records with your new imaging clinic can help the radiologist interpret your current scan more accurately.
Schedule Your Low-Dose CT Lung Cancer Screening
American Health Imaging makes it easy to get answers about your lung health. We offer low-dose CT lung screening at up to 60% less than hospital-based imaging. Every scan is reviewed by a subspecialized, board-certified radiologist trained in thoracic imaging.
Our imaging services are available at locations across Georgia, Alabama, Texas, South Carolina, and Florida. We also offer same-day and next-day appointments, with extended hours at many centers.
Talk to your doctor about imaging and schedule your low-dose lung CT scan with American Health Imaging today.