Identification and Diagnosis Chapter 3: Diagnostic Workup

Watch Chapter 4 here.

Hello, and welcome to this program. 

In this session, we’ll discuss how to identify interstitial lung disease, or ILD, in patients with systemic autoimmune rheumatic disease, or SARD. These conditions include rheumatoid arthritis, systemic sclerosis, inflammatory myopathy or myositis, mixed connective tissue disease, and Sjögren disease. 

The goal today is to walk through the diagnostic pathway—pulmonary function testing, or PFTs, high-resolution computed tomography, or HRCT, and multidisciplinary discussion—and to show how this plays out in a patient scenario. 

To bring this to life, I want to introduce you to Maria. 

Maria is a 48-year-old woman with seropositive rheumatoid arthritis, or RA. Recently, she’s noticed something new: progressive exertional shortness of breath and a persistent dry cough. These symptoms have been present for several months. They’re nonspecific, and they haven’t gone away. 

Today, we’ll keep coming back to Maria as our guide. She represents many patients we see in the clinic—someone with well-controlled joint disease who suddenly develops respiratory symptoms. 

Once you have a suspicion, what’s next? That would be imaging.  HRCT is the gold standard of imaging modality.

For Maria, if her HRCT shows basilar, subpleural reticulation with traction bronchiectasis, maybe even honeycombing, that would suggest a UIP pattern. If instead we see more ground-glass change with subpleural sparing and increased reticulation, that would suggest nonspecific interstitial pneumonia. Each pattern has implications for prognosis and management.  

Next comes pulmonary physiology. 

PFTs, including spirometry, lung volumes, and diffusing capacity of the lungs for carbon monoxide, or DLCO, are the next logical steps. 

It is important to note that PFT should be performed alongside HRCT as an essential screening step. 

A reduced DLCO can be the very first abnormality in ILD, even when spirometry appears to be normal. Studies have shown that isolated reductions in DLCO may precede radiographic evidence of disease in systemic sclerosis and dermatomyositis and are frequently the only physiologic marker of early ILD. 

This is clinically relevant to Maria. Even if her spirometry shows preserved lung volumes, a low DLCO would support our suspicion that her symptoms are lung-based rather than simply deconditioning. 

DLCO is influenced by alveolar volume, hemoglobin, and the diffusion coefficient for carbon monoxide. Interpreting DLCO alongside the carbon monoxide transfer coefficient and alveolar volume, as well as correcting for hemoglobin, helps prevent misinterpretation. This correction matters because anemia or low hemoglobin can falsely lower DLCO, mimicking diffusion impairment even when lung function is normal. An isolated low DLCO, particularly when corrected values remain reduced, should not be ignored. It should prompt further evaluation for early interstitial or pulmonary vascular disease, such as pulmonary hypertension.

How do we put the pieces together? This is where multidisciplinary discussion, or MDD, comes in. 

MDD improves diagnostic confidence and inter-clinician agreement by integrating all available data—clinical history, high-quality HRCT, autoimmune serologies, and pulmonary physiology.

Even if your institution doesn’t have a formal multidisciplinary discussion, the principle still applies. A brief, structured conversation with a pulmonologist or radiologist can still be helpful by aligning clinical impressions, imaging interpretation, and next steps. What matters most is sharing expertise across specialties, whether that happens in a conference room or a quick consultation call. 

For Maria, this means her rheumatologist, pulmonologist, and radiologist should connect—whether formally in an ILD clinic or even informally with a shared review. This could be as simple as a quick text or call with rheumatology, pulmonology, or radiology.  

It’s worth emphasizing that invasive testing is not routine. 

Surgical lung biopsy should be reserved for situations where HRCT and clinical data are insufficient or discordant. However, if there is a concern for malignancy or another diagnosis that cannot be resolved noninvasively, it may be necessary to proceed to an open lung biopsy.  

In many patients, including Maria, if their HRCT and clinical picture line up, then PFTs, HRCT plus clinical features, and laboratory data are enough to make a confident diagnosis of underlying interstitial lung disease. That can spare the patient from open lung biopsy and surgical complications. 

Thank you for watching. 

We’ve followed Maria’s story from her first nonspecific symptoms through the red flags, risk stratification, diagnostic testing, and multidisciplinary review. 

Maria’s case illustrates the broader lesson: early suspicion, structured evaluation, and collaborative care make the difference. 

If you adopt this pathway in your clinic—screen, test, image, and discuss early—you’ll help patients like Maria avoid delays and receive the care they need. 

For more resources, please visit the Rheumatology and Arthritis Learning Network. 

6MWT – Six-minute walk test 
ANA – Antinuclear antibody 
Anti-CCP – Anti–cyclic citrullinated peptide antibody 
Anti-Ro52 – Anti-Ro/SSA autoantibody 
CTD-ILD – Connective tissue disease–associated interstitial lung disease 
DLCO – Diffusing capacity of the lungs for carbon monoxide 
FVC – Forced vital capacity 
GGO – Ground-glass opacity 
HRCT – High-resolution computed tomography 
IIM – Inflammatory idiopathic myopathy / inflammatory myositis 
ILD – Interstitial lung disease 
IPF – Idiopathic pulmonary fibrosis 
L – Liters 
LIP – Lymphocytic interstitial pneumonia 
MCTD – Mixed connective tissue disease 
MDD – Multidisciplinary discussion 
MDT – Multidisciplinary team 
NSIP – Nonspecific interstitial pneumonia 
OP – Organizing pneumonia 
PFT – Pulmonary function test 
PPF – Progressive pulmonary fibrosis 
RA – Rheumatoid arthritis 
RF – Rheumatoid factor 
SARD – Systemic autoimmune rheumatic disease 
SSc – Systemic sclerosis 
SS – Sjögren disease 
sec – Seconds 
UIP – Usual interstitial pneumonia 
VA – Alveolar volume 

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