New Guideline Updates Diagnostic Criteria for IPF

An updated clinical practice guideline for diagnosing interstitial pulmonary fibrosis (IPF) defines four diagnostic categories on the basis of lung imaging and provides specific testing pathways for each of them.

Clinicians should first obtain a detailed history of medication use and environmental exposures to exclude potential causes of interstitial lung disease (ILD) and conduct serologic testing to exclude connective tissue disease as a cause, the authors write.

Next, all patients with newly diagnosed ILD should undergo high-resolution computed tomography (HRCT) of the chest to determine whether the images indicate a usual interstitial pneumonia (UIP) pattern, probable UIP, an indeterminate pattern, or an alternate diagnosis, according to the guideline, which was published online and in the September 1 issue of the American Journal of Respiratory and Critical Care Medicine.

When scan patterns point to probable UIP or indeterminate or alternate diagnosis, patients should undergo bronchoalveolar lavage and surgical lung biopsy, but there is insufficient evidence to recommend for or against transbronchial lung biopsy or lung cryobiopsy in these patients, Ganesh Raghu, MD, chair of the guideline committee and director of the Center for Interstitial Lung Disease at the University of Washington in Seattle, and colleagues write.

In contrast, neither cellular analysis of bronchoalveolar lavage fluid nor surgical lung biopsy are recommended for patients with a UIP pattern, as the downsides of the procedure outweigh potential benefits. In addition, the guideline committee strongly recommends against transbronchial lung biopsy and lung cryobiopsy in these patients.

Although lung cryobiopsy has been shown to produce a high diagnostic yield, "this was offset by concern about the lack of standardized procedure and approach and the heterogeneous rates of adverse events noted in previous studies," the authors write. "The panel identified many questions that need to be answered before recommending widespread use of cryobiopsy, including: How many specimens should be obtained to optimize diagnostic yield while minimizing complications? From which portion of the lung should they be obtained in relation to the microanatomy of the lung and diseased lung tissues? For how long should the probe be cooled?"

It is reasonable, however, for experienced experts with a track record of performing lung cryobiopsy safely to continue to do so in patients whose HRCT pattern is probable UIP, indeterminate, or an alternative diagnosis, the authors explain.

Multidisciplinary Discussions for Decision-Making Recommended

The guideline also addresses multidisciplinary discussions (MDD) for decision-making and serum biomarkers. Specifically, the committee recommends MDD for patients with newly detected ILD of unknown cause who are clinically suspected of having IPF because the available evidence suggests that as many as 300 patients may be subject to incorrect therapy, delayed therapy, or unnecessary additional diagnostic testing, a finding "deemed unacceptable," the authors write. Further, MDD is likely to be of greatest benefit for patients with HRCT patterns indicating probable UIP, indeterminate, or an alternative diagnosis, "or when there exist discordant clinical, radiologic, and/or histologic data."

Although there are insufficient data to define what optimal MDD entail, they should consist of an interaction between a pulmonologist (and rheumatologist on a case-by-case basis), radiologist, and pathologist, the authors write. The revised categorization should facilitate more streamlined discussions among multidisciplinary team members, they note.

Serum Biomarker Measurement Not Recommended

With respect to serum biomarkers, the committee recommends against measuring serum matrix metalloproteinase 7, surfactant protein D, chemokine ligand 18, or Krebs von den Lungen 6 for the purpose of distinguishing IPF from other ILDs. "For the time being, the guideline panel dismissed serum biomarker measurement as an approach to distinguishing IPF from other ILDs because of the high false-positive and false-negative result rates," the authors explain.

The new guideline was jointly developed by the American Thoracic Society, the European Respiratory Society, the Japanese Respiratory Society, and the Latin American Thoracic Society to update the previous guidelines issued by the societies in 2011.

On the basis of their review of the available evidence, the panel members conclude that there is "an urgent need" to refine and validate diagnostic approaches in ILD. "These needs can be roughly categorized as investigations into the roles of clinical observations, HRCT, bronchoscopy, histopathology, and biomarkers," they write.

Several authors report multiple types of financial relationships with numerous companies. For the full list of disclosures, please see the journal website.

Am J Respir Crit Care Med. Published online September 1, 2018. Abstract

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