Ryan Haumschild, PharmD, MS, MBA: Speaking of incidence—that’s what I was asking for— how often does it occur? It’s important to understand the incidence and the prevalence of interstitial lung disease [ILD] by subtype. Dr Noble, if you can walk us through, how does the incidence occur across the different subtypes that Dr Culver spoke about earlier? What are some things you’re seeing? Is it becoming more prevalent or less prevalent? How are you picking up on it within your practice?

Paul Noble, MD: In my world, because I’m a 1-trick pony caring only for patients with ILD, it’s an epidemic. But ILDs are not rare. By the numbers, it’s generally said [that there are] about 20 per 100,000 incidents or new cases in a year. In terms of the prevalence of existing cases, it’s maybe 100 per 100,000. So there are about 50,000 diagnosed and well over 100,000 patients who have some form of interstitial lung disease. That’s typically for IPF [idiopathic pulmonary fibrosis]. If you broaden the numbers for connected tissue disease–related ILD and chronic hypersensitivity pneumonitis [HP], these are not uncommon diseases. Maybe it’s because of the rarefied world I practice in between the edge of West Hollywood and Beverly Hills [California]. It seems like every time somebody sneezes, they get a CT scan. When I was a fellow 30 years ago, we used to call them last rites consults, because we’d see these patients who’d been sick for years and years. But now we’re seeing a lot of patients whose big complaint, quite honestly, is they’re struggling in their third set of tennis. How do we handle that? How do we deal with this early onset disease? It’s a tremendously exciting time.

The other reason the disease is being recognized more is that we have treatments. In 2014 we had the first FDA-approved drugs for idiopathic pulmonary fibrosis. Now there’s approval for other indications with fibrotic lung disease. There’s a reason to find patients. It used to be that it didn’t matter—what were we going to do? Give steroids, and people were largely going to feel terrible. There’s been a tremendous growth in the detection of ILDs over the last decade.

In terms of the breakdown, I have to think about my clinic every week. It seems like about a third of the patients have IPF and a third have chronic HP. In California, I’ve been struck, and it may be different in Cleveland [and other] parts of the country. I’ve seen more chronic HP in my 9 years in Los Angeles than I saw in Durham, North Carolina; New Haven, Connecticut; and even as a fellow in Denver [Colorado]. In LA, everybody has birds and hot tubs, so there’s a little craziness going on. But there’s something about the air; it seems to carry spores better. I don’t know what it is, but I see a tremendous amount of chronic HP, and distinguishing that from IPF in my hands is a real struggle. I really struggle with that. Then about a third are connected tissue disease.

To add to what Dr [Kristin] Highland said, 1 thing that has struck me, because I’ve been doing this for so long, is that some patients will come with a fibrotic disease, but their rheumatologic diagnosis can come 5, 10 years later. That’s 1 thing I struggle with. Is this a forme fruste of a connective tissue disease? Because we’re going to treat them fundamentally different from [someone with] IPF. That’s very common. These rare autoimmune diseases, the antisynthetase or the interstitial pneumonitis with autoimmune features. We don’t even know exactly what that is, but this is the world we live in. We send the patient to the rheumatologist, and they can’t check off enough boxes to give them rheumatologic lung disease. But we’re going to treat them with prednisone and maybe mycophenolate because we think there’s an underlying connective tissue disease. That’s 1 reason why it’s so fascinating. Generally break it down to a third, a third, a third.

Ryan Haumschild, PharmD, MS, MBA: I love the context you gave around how we’re diagnosing and recognizing these patients and seeing these early indicators for other comorbidities. We’re trying to connect the dots. As you said, [sometimes there are] just not enough dots to check. We know sometimes that comes into payer restrictions on how we treat those patients, and it’s important to think about that as we code it for an ICD-10 [International Classification of Diseases, 10th revision] code.Dr Culver, I want to call on you to weigh in maybe a little about what Dr Noble talked about.

Daniel Culver, DO: I agree with everything Paul and Kristen said. I just looked at these data for our place, and we have pretty similar breakdowns, perhaps a little less IPF as a proportion. Maybe closer to 30% and then pretty even between chronic hypersensitivity pneumonitis and connective tissue disease. There are a couple of other ones that are not uncommon. One is unclassifiable interstitial lung disease, which in various series is between 10% and 20%. That’s after everything we do and sending the patient to Dr Noble for all the extensive experience in testing that he will do. We still can’t come down and put our nickel on a particular diagnosis. That points to 1 key factor that we’re learning about and that we’re looking at in ILD, which is that the behavior of the disease is in many ways just as important as putting a label on the first day or the first month that you evaluate the patient. The longitudinal trajectory and the response to treatment inform our thinking about the patient.

With regard to how the patients are coming in, it’s evolving a little. Paul alluded to this. As you know, lung cancer screening is now approved. Lung cancer screening is going to be approximately double the population that’s able to avail themselves of lung cancer screening. If you come into the ED [emergency department] with a stubbed toe, you have a PE [pulmonary embolism] protocol CT. We used to do abdominal exams, and now you get a CT for any belly symptom. We’re seeing a lot of patients with interstitial changes.

One thing I want to highlight is the importance of referral to a center that’s used to evaluating patients with these things. A concept that’s evolved in the last decade is called interstitial lung abnormalities, which is interstitial changes on imaging with similar genetics, impairments of physiology, and some of the same imaging features. But it’s much more prevalent than a disease like IPF. It’s clear that not every person with ILA has a bad phenotype and is going to progress. As Kenny Rogers said, you got to know when to hold them and know when to fold them. Going to a center that has a little experience with that is very important, and in IPF it’s been shown several times that earlier referral to an experienced larger center does associate with better outcomes. That can mean not doing things as much as it can mean doing more things. Not doing surgical biopsies, but being comfortable with the imaging, not jumping on medications right out of the gate but being comfortable watching. That’s one thing I wanted to emphasize.

This transcript has been edited for clarity.