June 10, 2011

Background

Idiopathic pulmonary fibrosis (IPF) is a progressive interstitial process of increasing prevalence. The American Thoracic Society recently collaborated with three international specialty societies to update diagnostic and therapeutic practice guidelines for this condition.

Conclusions

IPF usually presents after age 50 years with unexplained exertional dyspnea, cough, bibasilar crackles, and clubbing. This condition is more common in men and cigarette smokers. Occupational exposure to dusts from metal, wood, and other organic materials have some association with IPF.

Prevalence studies have given widely different estimates because of past difficulties with diagnosis.

Critical elements to diagnose IPF include usual interstitial pneumonia (UIP) on high-resolution CT scan of the chest and exclusion of other causes of chronic fibrosis such as pneumoconiosis (for example, asbestosis, hypersensitivity pneumonia, and systemic connective tissue disease). UIP is characterized by predominantly basal and peripheral patchy reticular opacities and honeycombing.

Pathologic findings include moderate inflammation with lymphocytes and plasma cells in septal and subpleural tissue. Areas of scarring demonstrate dense fibrotic tissue with occasional zones of proliferating fibroblasts.

IPF usually results in a progressive decline in functional status and pulmonary function. While some studies estimate an average survival of 2-3 years after diagnosis, this outcome can be quite variable depending upon pulmonary function at the time of clinical delineation.

The diffusing capacity for carbon monoxide has fairly reliable predictive value of survival at baseline with patients under 40% of predicted having worse outcomes. A 5% or 10% decline over 6 months in forced volume vital capacity tests or a 1-year drop of more than 15 mm Hg in the A-a oxygen gradient can also predict increased mortality risk.

Less than 5% of IPF is attributed to genetic factors.

Implementation

Classic findings of IPF on high-resolution chest CT can preclude the need for surgical biopsy, especially in patients with impaired physiologic reserve.

Chest x-rays are usually less effective in the diagnostic process for IPF than high-resolution CTs are.

The presence of pleural abnormalities such as plaques and calcification, pleural effusion, micronodules, nonhoneycombed cysts, or consolidation on radiologic examinations should promote consideration of other diagnoses.

Symptomatic presentation in women and patients under age 50 years should prompt aggressive evaluation for an underlying connective tissue disorder.

Bronchoalveolar lavage followed by a differential cell count that demonstrates lymphocytosis greater than 40% should prompt additional workup for hypersensitivity pneumonia, which can be seen in approximately 10% of patients with UIP x-ray findings.

Transbronchial biopsy is generally not useful in the evaluation of patients with suspected IPF.

While clinical evidence is not definitive to support their use, basic serologic testing for connective tissue disease is often appropriate in the evaluation of these patients.

There are no definitive therapeutic interventions for this disease. Corticosteroid monotherapy should not be used in the treatment of IPF. While colchicine can inhibit fibroblast proliferation, prospective clinical trials have not demonstrated improved outcomes with colchicine in IPF.

Strong clinical evidence recommends against the use of interferon-gamma-1b in the treatment of these patients.

Based on current clinical evidence, there is a strong rationale against the use of the following agents to treat IPF: cyclosporine A, corticosteroids plus an immune modulator, bosentan, and etanercept.

There is clinical evidence against using the following agents to treat IPF: acetylcysteine, acetylcysteine plus azathioprine and prednisone, pirfenidone, and anticoagulation.

Treatment of pulmonary hypertension associated with IPF has not been shown to offer substantial benefit to most patients.

While clinical evidence is not strong, it is reasonable to treat asymptomatic gastroesophageal reflux.

While long-term studies have not demonstrated outcome change, patients with hypoxemia should receive chronic, supportive oxygen therapy.

Patients with respiratory failure secondary to their chronic progressive disease should not receive mechanical ventilation.

More than half of patients with IPF who undergo lung transplantation survived 5 years. Patient selection and timing of transplant are important elements in good outcome.

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