Increasing numbers of patients are being diagnosed with interstitial lung diseases (ILD), especially idiopathic pulmonary fibrosis (IPF). IPF is an important disease where excessive scar tissue forms in the lungs. This leads to impaired lung function and the patient experiences increasing breathlessness, hypoxia and ultimately death. The median survival (before the advent of anti-fibrotic drugs) was two to five years from diagnosis, similar to that of many lung cancers. 

It is poorly understood why the incidence is increasing or indeed what causes this disease. A British Lung Foundation report from 2015 estimated that 15,000 people in the UK are living with IPF. The Irish Thoracic Society believes that there may be 2,000 people with IPF in Ireland and many thousands of patients with an ILD of some type.¹

Clinical evaluation in primary care

The diagnosis of an ILD is challenging as the principal symptoms, shortness of breath and cough, are very non-specific. But certain features may be helpful in alerting the clinician to a possible diagnosis including:

•Progressive shortness of breath on exertion (in the absence of another explanation)

•Dry cough that does not respond to antibiotics and simple measures

• Finger clubbing

•Crackles, especially dry or Velcro-like crackles heard on lung auscultation during inspiration. These are often best heard at the lung bases and in the axillary areas. 

A detailed history focusing on the following elements may give some clues as to patients at higher risk for ILD in general but it should be remembered that the cause of IPF remains unknown.

•Age: The majority of IPF patients diagnosed are over 50 years of age. However patients can present at younger ages especially in familial disease and IPF is commonly diagnosed in patients over 80 years old. 

•Medical history: Comorbidities, eg. rheumatoid arthritis or connective tissue diseases like scleroderma

•Medication prescribed: eg. amiodarone and nitrofurantoin 

•Social history 

–Smoking history (many patients with IPF are current or former smokers)

–Occupation history, eg. asbestos,² dust, fumes or chemical exposures

–Environmental exposures, eg. birds, dampness/mould, hot-tubs and humidifiers or other exposures where the patient inhales organic antigens leading to a reaction in the lung (hypersensitivity pneumonitis).

Further evaluation

Oxygen saturations 

Pulse oximetry is useful but saturations remain normal (especially at rest) in the early stages of disease. Re-checking saturations after a short walk or exertional activity, such as climbing of stairs, may be helpful in detecting exercise-induced desaturation, which is a significant finding. Normal oxygen levels do not exclude ILD.

Chest radiology

A chest x-ray is indicated if respiratory symptoms of any kind persist for more than three weeks. However, the chest x-ray may be normal in as many as 10% of patients with ILD. If the patient is symptomatic and other features like crackles are present, referral for a CT thorax should be considered. CT is much more sensitive for detecting interstitial abnormalities than chest x-ray. 

Referral to respiratory medicine

This is appropriate if the diagnosis is unclear or in cases where there is an abnormal chest x-ray or CT scan. Details including the level of exertion at which the patient is breathless, the oxygen saturations, clinical findings and chest x-ray findings are very helpful to allow the hospital team to appropriately triage referrals. 

Interstitial lung diseases are complex conditions and accurate diagnosis is important. International best practice recommends a multidisciplinary approach where respiratory physicians, radiologists and pathologists discuss individual patients to arrive at a diagnosis.

Pharmacological treatment 

The treatment of IPF has changed completely in the past few years with the arrival of two drugs in the new class of oral antifibrotic agents. These medicines are pirfenidone and nintedanib and are both available in Ireland on the hi-tech prescription scheme. 

IPF remains incurable; however studies have shown that both these agents slow the rate of disease progression and therefore represent a significant step forward. 

Other clinical trials looking at traditional treatment combinations that include steroids have shown they are harmful in IPF. Therefore empiric treatment with prednisolone is not appropriate in an undiagnosed ILD. Prednisolone and other immunosuppressive agents are still used in other conditions like sarcoidosis, so establishing an accurate diagnosis is key.

Resources and other considerations

The Irish Lung Fibrosis Association has information packets for patients that are extremely helpful and include information about patient support groups, exercise tools like pedometers (2000 Step Challenge)³ and information for patients and families.

In more advanced disease, oxygen therapy and palliative care are key resources that should be made available to all patients. Certain eligible patients with advanced disease will be referred for consideration for lung transplantation to the national centre at the Mater Hospital.

Some specialist centres in Ireland are conducting clinical trials examining new drugs that may be added to existing therapies in IPF and also in studying if the oral anti-fibrotic agents have a role in other fibrotic diseases like scleroderma-related interstitial lung disease

In summary, IPF, the most common and serious ILD, is being diagnosed with increasing frequency but the reasons for this are unclear. This disease carries significant morbidity and mortality with patients experiencing increasing breathlessness and ultimately hypoxic respiratory failure and death. The availability of a new drug class – the oral antifibrotic agents – has represented a significant step forward as these medicines slow the rate of disease progression. Furthermore, pooled data from clinical trials suggests they prolong survival. 

Identifying patients as early as possible so that they may benefit from these agents in addition to specific medical, nursing and physiotherapy support will benefit patients. 

Useful websites

• Irish Lung Fibrosis Association: www.ilfa.ie

• British Thoracic Society: www.brit-thoracic.org.uk

• Pulmonary Reaction to drugs: www.pneumotox.com