Current Challenges in Diagnosing Progressive Fibrotic Interstitial Lung Diseases

Introduction

Progressive fibrotic interstitial lung diseases (ILDs) represent a subgroup of interstitial lung diseases characterized by progressive fibrosis of lung tissue. In addition to the well-known idiopathic pulmonary fibrosis, this subgroup includes other diseases such as hypersensitivity pneumonitis, interstitial lung diseases associated with rheumatoid arthritis and systemic sclerosis, or idiopathic nonspecific interstitial pneumonia. 

Current Diagnostic Challenges

Delayed diagnosis of progressive fibrotic interstitial lung disease is partly due to the subtle and nonspecific symptoms of the disease, most commonly cough, shortness of breath, and fatigue. Another important factor is the lack of awareness of this group of diseases among general practitioners and specialists not focused on lung diseases. Thus, patients are often subjected to unnecessary and costly diagnostic procedures and ineffective and potentially harmful treatments.

Misdiagnosis as a Major Pitfall

According to a questionnaire survey conducted in the United States in 2018, the most common misdiagnoses in patients with fibrotic ILD were asthma (13.5%), pneumonia (13%), and bronchitis (12.3%). The correct diagnosis of the disease is thus established on average several years later; according to a questionnaire study conducted in Denmark on patients with idiopathic pulmonary fibrosis, the median delay in diagnosis was 2.1 years.

A potential solution to the problem is, first and foremost, greater awareness among physicians (and patients) about the clinical manifestation of progressive interstitial lung diseases. Suspicion of the disease should arise in all individuals with persistent symptoms (such as cough and shortness of breath) with a history of smoking, exposure to external risk factors, and especially a positive family history. Suspicious signs include the auscultatory finding of bilateral basal inspiratory crackles (crepitus, known as velcro crackles – the sound of unfastening dry zipper) and clubbing fingers. For these patients, an examination by a pulmonologist is recommended, involving imaging methods (preferably high-resolution computed tomography /HRCT/).

Screening: Yes or No?

Some diseases are currently detected incidentally during CT examinations for other reasons, such as in lung cancer screening, cardiac CT, abdominal CT, or angiography. Currently, there is no clear recommendation regarding screening methods, and standard population screening cannot be recommended at this time.

The only exception is systemic sclerosis. According to current recommendations, all patients with systemic sclerosis should undergo HRCT at the time of diagnosis and the examination should be repeated if new respiratory symptoms occur or if symptoms worsen to assess progression. In asymptomatic patients, follow-up examinations are performed based on individual risk factors. In patients with other connective tissue diseases, attention should focus on pulmonary symptoms during regular check-ups.

Significant attention is also directed to relatives of patients with familial or sporadic forms of progressive interstitial lung disease. First-degree relatives of patients with the familial form of the disease should undergo medical examination and possibly genetic testing; specialized examination may also be offered to other relatives. In relatives of patients with familial or sporadic forms, it is also advisable to recommend smoking cessation and avoidance of exposure to risk factors.

Gaps in Education

An important factor in delayed diagnosis is the awareness of the disease among the patients themselves. A questionnaire study conducted in Europe in 2019 revealed that 60% of patients with idiopathic pulmonary fibrosis visited a general practitioner within 3 months of symptom onset, though 29% waited longer than 6 months to seek medical advice. 

Conclusion

The diagnosis of progressive interstitial lung diseases is often delayed, associated with initial misdiagnoses, unnecessary examinations, and late initiation of adequate treatment. However, it is not yet sufficiently proven whether earlier diagnosis and treatment lead to better therapeutic outcomes.

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Source: Spagnolo P., Ryerson C. J., Putman R. et al. Early diagnosis of fibrotic interstitial lung disease: challenges and opportunities. Lancet Respir Med 2021; 9 (9): 1065–1076, doi: 10.1016/S2213-2600(21)00017-5.