Establishing a Diagnosis of Interstitial Lung Disease
Alicia M. Hinze, MD: Differential diagnosis very broadly, in terms of interstitial lung disease, really relies on a good history of environmental exposures, as well as a history of any features that could be consistent with autoimmune disease. When talking to patients who may be found to have interstitial lung disease on high-res CT [computed tomography] or were presenting with symptoms of shortness of breath and found to have interstitial lung disease, we’ll go through a very detailed history all the way—from whether they may have any exposure, such as coal, to whether they have a pet bird at home.
Then from a rheumatic perspective, we evaluate for other signs or symptoms of autoimmune disease to see if there may be an underlying autoimmune disease that may be associated with the interstitial lung disease. As a rheumatologist, I’m often asking people about whether they have color changes in their fingers in the cold that can be associated with something called Raynaud phenomenon and whether they have a lot of stiffness in the joints in the morning, in the small joints of the hands that could be associated with inflammatory arthritis. Just review other skin features, such as rashes or skin thickening, and other systems that could be involved in an autoimmune disease that could be driving the interstitial lung disease.
Of the diagnostic tools that we would use to really evaluate for interstitial lung disease, high-resolution CT certainly would really give us the fullest evaluation of what the interstitial lung disease looks like. Sometimes we can see it on chest x-ray. High-resolution CT is going to be more sensitive. Pulmonary function testing is critical for the evaluation of interstitial lung disease because this is really telling us whether there’s been any reduction in the actual lung function in the presence of interstitial lung disease. We look at parameters called forced vital capacity, which would often be reduced if the interstitial lung disease is really clinically relevant. And we’ll also look at diffusing capacity for carbon monoxide on the PFTs [pulmonary function tests], which can also be reduced in the setting of interstitial lung disease.
These have to be taken in context of other things that are going on with a patient. For example, if they have underlying pulmonary hypertension, which can be seen, we can also see a reduction in the diffusing capacity for carbon monoxide. It’s a complex evaluation, and we do use 1 clinical examination and the patient history of dyspnea. Although some patients cannot be incredibly symptomatic, we can still see interstitial lung disease. The high-resolution CT and pulmonary function testing are really the key features that we use in terms of examination and imaging parameters and procedures that we’ll use to really define that level of interstitial lung disease and how it’s affecting the patient.