As clinicians, we are keenly aware that guidelines on the diagnosis and treatment of a disease change, as continuous research provides additional clarity and information. In the UK, this is perhaps most poignantly reflected in the British National Formulary, which is essentially a book on the latest British guidelines for drug prescription. The book is updated a few times a year, each time with a cover of a different mystery color, which has become a guessing game of sorts among British healthcare professionals. 

We all know that no disease is exempt from guidelines changing every once in a while, even with some of the most common medical conditions such as hypertension. On the bright side, this proves that medicine is indeed a living discipline, with our diagnostic and treatment methods improving as new research comes to light. 

In this article, we will look at how the 2018 guidelines for the diagnosis of idiopathic pulmonary fibrosis (IPF), which had last been updated in 2011, have impacted clinical practice. An accurate IPF diagnosis is crucial because it dictates treatment in a disease that already suffers from very poor patient outcomes. Currently, diagnostic guidelines depend on a multidisciplinary approach, including a heavy reliance on history-taking, imaging, and laboratory findings. 

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South Korean researchers studied the impact of the 2018 change in diagnostic guidelines and published their findings in Scientific Reports. Has the change in guidelines resulted in measurable improvements in clinical outcomes? Let’s explore the answer to this question in detail in this article.

Guideline Updates

First, let’s look at what changed in the diagnostic guidelines from 2011 to 2018. The new guidelines were endorsed by 4 major bodies: the American Thoracic Society, the Japanese Respiratory Society, the Latin American Thoracic Society, and the European Respiratory Society; in other words, it is safe to say these guidelines received global assent.

There were two main areas in which the 2018 guidelines differed from that of 2011: 

  1. The proposed use of high-resolution computed tomography (HRCT) to refine the diagnosis and classification of usual interstitial pneumonia (UIP), including identifying patterns for UIP, probable UIP, indeterminate for UIP, and alternative diagnoses.
  1. The conditional recommendation of bronchoalveolar lavage (BAL) in patients with CT pattern of probable UIP, indeterminate for UIP and alternative diagnosis prior to surgical lung biopsy. This is to more conclusively distinguish IPF from other alternative diagnoses, such as eosinophilic pneumonia, sarcoidosis, and hypersensitivity pneumonitis.

The 2018 guidelines introduced new conditions for the use of BAL in diagnosing UIP, including IPF. In contrast, the Fleischner Society guidelines have a greater emphasis on the role of lung biopsies to reach a diagnosis. 

New Classifications

Researchers recruited 535 patients with fibrosing interstitial lung disease (ILD). HRCT scans were conducted in both the prone and supine positions. 

One major implication of the 2018 guidelines is in how UIP is classified. Patients who were classified as having possible UIP according to the 2011 guidelines were now reclassified into 2 new categories: probable UIP and indeterminate for UIP. 

According to the 2011 criteria, 219 patients were classified as having possible UIP; with the updated guidelines, 175 were reclassified as having probable UIP, 42 were reclassified as indeterminate for UIP, and 2 were reclassified as having an alternative diagnosis. In addition, a significantly higher proportion of patients was diagnosed with IPF by CT patterns that show UIP compared to CT patterns that show probable UIP. However, the difference between IPF diagnosis in patients with probable and indeterminate UIP was not significant. 

Read more about IPF prognosis

Another impact of the 2018 guidelines was in survival analysis. Patients reclassified as being indeterminate for UIP had significantly better survival than patients in other groups. In addition, researchers looked at whether BAL fluid analysis improved the diagnosis of IPF. They found that the emphasis on BAL fluid analysis in patients who were suspected to have IPF based on having an HRCT pattern of probable UIP, indeterminate UIP, or an alternative diagnosis had a positive impact on diagnosis. 

“In our study, the inclusion of BAL fluid analysis increased diagnostic performance, including specificity and positive predictive value (PPV), compared with a model that included CT pattern and appropriate clinical features increasing the likelihood of IPF, ie old age and male,” wrote the authors of the study. 

Where does this leave the role of lung biopsy in diagnosis? In the case of patients with probable UIP, researchers found that “there still can be a significant heterogeneity of underlying disease that certain proportion of idiopathic non-specific interstitial pneumonia (iNSIP) also can show similar CT findings.” This led them to argue in favor of forgoing lung biopsy in patients with probable UIP based on CT patterns.

Improved Diagnostic Performance

Overall, the researchers of this study were confident that the 2018 diagnostic guidelines were an improvement from the guidelines from 2011. Particularly, they found that BAL fluid analysis was incredibly valuable in improving the diagnostic certainty of IPF in patients with probable UIP according to patterns observed on their CT scans. 

The success of the 2018 guidelines in better diagnosing patients with IPF strongly supports the case for the periodic review and improvement of diagnostic and treatment guidelines of all diseases when new research comes to the surface. In all likelihood, scientists are already currently working on a new set of IPF diagnostic guidelines that will improve on the ones set in 2018. 


Choe J, Kwon BS, Do KH, Hwang HS, Song JW, Chae EJ. Diagnostic and prognostic implications of 2018 guideline for the diagnosis of idiopathic pulmonary fibrosis in clinical practice. Sci Rep. Published online August 13, 2021. doi:10.1038/s41598-021-95728-7

Our organisation and history. BNF Publications. Accessed August 24, 2021.