Coloured 3D computed tomography (CT) scan of healthy lungs, showing the main bronchi (pink) and bronchioles (light blue).Credit: Vsevolod Zviryk/ Science Photo Library
As a pulmonologist, Chao He has witnessed the long road that many people have to take on their way to a diagnosis of idiopathic pulmonary fibrosis (IPF).
IPF causes progressive scarring of the lungs that makes it increasingly difficult to breathe and its cause is unclear. It often starts with a persistent cough. Typically, people with such symptoms are initially treated for pneumonia or bronchitis. After a couple of months without relief, the person might receive a lung X-ray, but this is usually inconclusive. Sometimes, a cardiologist checks whether heart failure is causing the person’s shortness of breath. This leads to an echocardiogram, then an angiogram and possibly the placement of a stent in their arteries. Eventually, the person sees a pulmonologist, who performs lung-function tests to measure breathing and sometimes a lung scan. Only then — typically a year or two after the first symptoms — is a diagnosis of IPF delivered, says He.
In that time, the disease has advanced. By the time the person eventually receives a diagnosis, they might have only 3–5 years left to live. “IPF is a pretty deadly disease,” says He.
Nature Outlook: Lung health
Of course, diagnosis is not an end in itself, but rather a necessary step before the right treatment can be chosen. But in the case of pulmonary fibrosis, diagnostic delay has particular consequences. Nothing can reverse the scarring that has already occurred, but there are antifibrotic drugs that can slow the progression of the condition. The earlier that those can be prescribed, the sooner that lung function can be stabilized and the longer the person might live.
Scientists are working on ways to identify IPF at an earlier stage. Those efforts include new ways to image lung tissue, the use of artificial-intelligence systems to analyse and improve existing imaging, and earlier and more widespread screening.
One important step in diagnosing IPF is ruling out other interstitial lung diseases (ILD). These diseases can cause inflammation and progressive scarring of lung tissue, but their causes are mostly known and treatments differ. Some cases of lung fibrosis, for example, stem from autoimmune diseases, such as rheumatoid arthritis or lupus. For people with these conditions, immunosuppressive therapy to address the underlying condition also resolves the fibrosis1.
In other cases, environmental factors might be to blame. Pulmonologists often ask people with fibrotic lungs whether they work on a chicken farm, because exposure to feathers can cause allergic reactions. If that or other environmental factors, such as smoking or particulate matter, are causing the lung damage then the best treatment is avoiding the irritant.
Better stratification of prognosis for IPF could lead to better treatments, says Elizabeth Estes, a business strategist who runs the Open Source Imaging Consortium (OSIC), a non-profit group in Saugatuck, Michigan, that collects and curates lung-imaging data for machine-learning algorithms. If computers can learn to predict who will respond to treatments, that could allow pharmaceutical companies to select the best candidates for clinical trials of drugs.
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