J: What are the stages of pulmonary fibrosis?

Pulmonary fibrosis isn’t formally “staged,” but doctors often describe it as mild, moderate or severe based on symptoms, lung function and imaging. Forced Vital Capacity (FVC) helps guide this: above 80% is mild, 50 to 80% is moderate, and below 50% is severe. Disease progression varies—some remain stable, while others worsen more quickly.

 

🎥 Watch the Video: What are the stages of pulmonary fibrosis?

 

Professor Porter discusses the following:

• What are the stages of pulmonary fibrosis?
• How do you define the stages of pulmonary fibrosis?
• Can lung function tests help in staging pulmonary fibrosis?

 

Full Video Transcript

We’re often asked this and, to be honest, as clinicians, we don’t really ‘stage’ pulmonary fibrosis.

We recognise that there are patients with changes on the high resolution CT scan but no symptoms. These patients, strictly speaking, don’t have idiopathic pulmonary fibrosis or any sort of pulmonary fibrosis. But they have residual lung abnormalities, which we do need to keep an eye on to make sure they don’t progress.

But, once you actually have a diagnosis of interstitial lung disease or pulmonary fibrosis, we recognise early disease or mild disease, and then moderate disease, and then more severe disease. And, usually, we define whether you are mild, moderate or severe, depending on your symptoms and your lung function and your imaging.

But very, very crudely, if you have a forced vital capacity, which is one of the lung function tests, of above 80%, then we would say you have very ‘mild’ disease. If you have a lung function forced vital capacity of 50 to 80%, then we would say you have ‘moderate’ disease. And, if your forced vital capacity (or FVC) is less than 50%, then we would say you have ‘severe’ disease.  I think that’s a reasonably good demarcation in the stages of pulmonary fibrosis.

But, unlike other diseases, you don’t necessarily progress through the stages. You might have mild disease and stay mild, or you might very quickly progress to severe.

 

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[Video published December 2025]