Screening and Monitoring Chapter 3: Monitoring and Defining Progression

Watch Chapter 4 here.

Hello, and welcome back to the ILD Explainer Video Series. I am Dr Elana Bernstein, an associate professor of medicine at Columbia University Vagelos College of Physicians & Surgeons and an associate attending at New York-Presbyterian Hospital. I am also the founder and director of the Columbia University/New York-Presbyterian Scleroderma Program. 

This series focuses on screening and monitoring ILDs. In this video, we’ll simplify the 2023 American College of Rheumatology—known as ACR—and the American College of Chest Physicians—known as CHEST— recommendations into practical clinic tools, outline disease-specific screening intervals and monitoring thresholds, demonstrate what progression looks like on tests and imaging, and share workflow strategies to embed these guidelines into daily practice. 

Now that we’ve established a baseline and screening protocol, the next question is: “How do we define progression?” 

While there are several definitions of progression, the ACR/CHEST 2023 guidelines define progression of ILD as any of the following occurring within 24 months:  

• An absolute decline in FVC of 10% or more. 

• A smaller decline of 5% to less than 10% when accompanied by worsening respiratory symptoms or increased fibrosis on HRCT.  

• Worsening symptoms with radiologic progression alone, even if PFTs remain stable. 

Beyond these thresholds, other recognized measures also help capture progression. An absolute decline in DLCO of 10-15%, a decrease in the 6-minute walk distance of more than 50 meters,or worsening of dyspnea and quality-of-life scores can all indicate meaningful physiologic change.

Importantly, these physiologic markers reflect different aspects of lung function. FVC measures lung volume, the total amount of air a patient can forcibly exhale after taking the deepest possible breath. It is a direct indicator of lung restriction and fibrosis. A decline of 10% or more in FVC is considered clinically significant because it reflects a measurable loss of lung capacity over time and correlates with worse outcomes in ILD.

DLCO measures how effectively gases transfer across the alveolar–capillary membrane. A 10% to 15% drop in DLCO suggests worsening gas exchange that could be due to increasing fibrosis or vascular involvement, among other reasons. Monitoring both FVC and DLCO together provides a more complete picture of disease behavior; FVC reflects restriction, while DLCO detects impaired diffusion that may appear earlier than volume loss. 

If we review Maria's PFTs over the past 12 months, her FVC declined by more than 10%. 

Additionally, Maria experienced a 16% drop in DLCO over the same period, indicating a decline in her lungs’ ability to transfer oxygen efficiently. Together, these results confirm objective physiologic progression. 

Recognizing these changes early provides clear, measurable criteria for determining when ILD is worsening. The goal is consistent, standardized monitoring that allows clinicians to identify progression confidently and act promptly to maintain stability and preserve lung function over time. 

Progression should also be assessed radiographically. On HRCT, findings such as new or increased reticulation, traction bronchiectasis, honeycombing, or more extensive fibrosis confirm disease progression. 

Smaller physiologic declines or subtle HRCT changes can precede more pronounced deterioration. That is why serial monitoring is essential—evaluating trends across symptoms, pulmonary function, and imaging provides the clearest distinction between stability and progression. 

Due to the concerning PFT results, a follow-up HRCT was ordered. Maria’s baseline HRCT showed only limited ground-glass changes, which were closely monitored over time. One year later, her repeat scan revealed increased reticulation and early honeycombing, confirming measurable radiographic disease progression.  

From a management standpoint, this emphasizes the importance of structured, serial assessment. Changes like those seen in Maria’s HRCT highlight the importance of repeating HRCT when symptoms evolve or pulmonary function tests worsen. 

Monitoring extends beyond confirming disease—it helps define its trajectory. Tracking the pattern and rate of physiologic and radiologic change allows clinicians to stratify risk, coordinate care with pulmonology, and plan follow-up frequency based on objective evidence of progression. 

In Maria’s case, her year-over-year comparison of HRCT and PFT data illustrates how management depends on recognizing trends early, maintaining consistent follow-up, and documenting change across modalities rather than responding to a single result. 

These thresholds matter because they provide an objective basis for adjusting care and escalating referrals. 

Maria’s case illustrates how structured assessment and regular monitoring can change the disease trajectory, allowing us to intervene earlier and preserve lung function.  

The final step is to embed these recommendations into daily clinical workflow, whether through EMR prompts, standardized order sets, or routine checklists, so that screening, monitoring, and defining progression become second nature in practice. This way, we can translate guidelines into better outcomes for patients. 

For Maria and your patients, these steps can make all the difference. 

Guidelines are not obstacles—they are tools. Use them confidently, and you can change the course of ILD for your patients. 

6MWD – 6-minute walk distance 
ACR – American College of Rheumatology 
Architectural distortion – Irreversible displacement of normal lung structures due to fibrosis 
CHEST – American College of Chest Physicians 
CTD-ILD – Connective tissue disease–associated interstitial lung disease 
DLCO – Diffusing capacity of the lung for carbon monoxide 
EMR – Electronic medical record 
FVC – Forced vital capacity 
GGO – Ground-glass opacity 
HRCT – High-resolution computed tomography 
IIM – Idiopathic inflammatory myopathy 
ILD – Interstitial lung disease 
MCTD – Mixed connective tissue disease 
MDD – Multidisciplinary discussion 
NSIP – Nonspecific interstitial pneumonia 
OP – Organizing pneumonia 
PFT – Pulmonary function testing 
PPF – Progressive pulmonary fibrosis 
Progression (ILD) – Worsening physiologic, radiologic, or symptomatic disease over time 
RA – Rheumatoid arthritis 
Radiologic progression – Worsening fibrotic features on HRCT 
Reticulation – Network of fine linear opacities caused by septal thickening 
SARD – Systemic autoimmune rheumatic disease 
SjD – Sjögren disease 
SSc – Systemic sclerosis 
Traction bronchiectasis – Irreversible airway dilation due to fibrotic pulling 
UIP – Usual interstitial pneumonia 

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