CPFF fellow investigates unclassifiable ILD

CPFF fellow investigates unclassifiable ILD

A native of Winnipeg, Dr. Leigh Minuk made her way to Toronto to complete her residency in internal medicine and then respirology. While at Toronto General Hospital, she became familiar with ILD patients and their struggles and was determined to help make a difference in their lives.

As a CPFF Robert Davidson fellow from September 2022 to September 2023, she honed her clinical and teaching skills and undertook a research project looking at the clinical and radiological characteristics of patients with unclassifiable interstitial lung disease (ILD), which is how about 10 per cent of ILD patients are categorized.  

“When we cannot determine a specific ILD diagnosis, it poses various challenges for patients and their health care providers in creating a treatment plan and estimating a prognosis,” says Dr. Minuk. “It can be unsettling and stressful for patients, when we cannot make a more precise diagnosis, and tell them exactly type of ILD they have.”

By reviewing data from the CARE-PF registry, Dr. Minuk and the research team, sought to characterize this group of patients and identify factors that are associated with a diagnosis of unclassifiable ILD. This retrospective study involved 1,593 cases in total, of which 157 patients (about 10 per cent) were determined to have unclassifiable ILD.  The data used by Dr. Minuk has been collected over the years for the CARE-PF registry and has involved ILD specialists, including several former CPFF Robert Davidson fellows.

This study involved the review of patient CT scans by a radiologist blinded to individual patient clinical characteristics, and then the categorization of the images based upon whether there was a confident pattern suggestive of a diagnosis. Then, clinical information (i.e., age, sex, smoking history, environmental exposures, connective tissue disease), was introduced and possible diagnoses were suggested based upon that discussion. If a confident diagnosis could not be reached, then they were labelled unclassifiable.

The study results included the following:

  1. Unclassifiable ILD is a common problem in the diagnosis and classification of ILD, with about 10 per cent of patients receiving a diagnosis of unclassifiable ILD after a multi-disciplinary discussion.
  2. A diagnosis of unclassifiable ILD was associated with worse survival when compared to patients with a specific ILD diagnosis. Those with unclassifiable ILD had similar survival to other fibrotic ILDs, such as idiopathic pulmonary fibrosis (IPF).
  3. Clinical characteristics and presence of a confident radiological pattern (from high resolution CT scans) are key features when establishing a confident clinical-radiological diagnosis of ILD, even when controlling for other factors.
  4. Lack of a confident imaging pattern was a major factor when the two leading diagnostic considerations were between IPF and fHP (fibrotic hypersensitivity pneumonitis) or when there were more than two leading differential diagnoses considered.

“While we suspected these findings based upon anecdotal clinical experience,” says Dr. Minuk, “the magnitude was more than anticipated. We found that the likelihood of arriving at a diagnosis of unclassifiable ILD is almost five times higher when there was no confident radiological pattern. This tells us that we continue to rely heavily on CT imaging patterns when making an ILD diagnosis.”

It poses a problem when there are unusual radiological characteristics, according to Dr. Minuk. This highlights the need for new advanced diagnostics other than CT scans, and a better understanding of who might benefit from specific therapies regardless of ILD categorization.

What do these results mean for patients, physicians and researchers? For patients with unclassifiable ILD, clinicians may consider beginning anti-fibrotic treatment as early as for they would for those with IPF, since the prognosis is similar. This would be expected to slow disease progression.

For researchers and clinicians, “we may want to look at developing additional diagnostic tools, like biomarkers, and establish local expertise in new imaging techniques, such as endobronchial optical coherence tomography” says Dr. Minuk.  

The study results were displayed in a scientific poster at the American Thoracic Society meeting in May this year. A corresponding paper will be submitted for publication, shortly. (This newsletter will let you know when the study is published and provide readers with a link.)

In addition to her research, Dr. Minuk is almost finished the requirements for a Graduate Diploma in Clinical Epidemiology at McMaster University, which provides a comprehensive overview of the fundamentals of clinical epidemiology.

Now living in Vancouver and taking up a new clinical position this month at Vancouver General Hospital, she’ll also be finishing up the manuscript for her fellowship research, as well as some clinical work at Toronto General Hospital.

We asked Dr. Minuk how the CPFF fellowship had improved her clinical skills. “General respirologists might only see a few pulmonary fibrosis cases out of every 100 patients. This experience gave me increased exposure to ILD patients and the knowledge to help them.”


Like all of our Robert Davidson Fellows, Dr. Minuk agrees that the support and funding of the CPFF fellowship is imperative to developing ILD specialists across the country. “It is an important contributor to making Canada a leader in ILD research and in community outreach, where we can share our expertise with local respirologists.”