Newer Blood Tests Could Replace Slower, Inaccurate Methods for Diagnosing PAP

Published February 2019 | Chest

For many years, the sheer rareness of pulmonary alveolar proteinosis (PAP) has made the syndrome hard to diagnose. This potential cause of lung failure occurs in just seven per one million people.

Most cases are misdiagnosed as pneumonia. That can leave people with PAP enduring 18 months or more of failed antibiotic treatments while undergoing a flurry of tests and procedures including pulmonary function tests, arterial blood gas analysis, chest radiographs, CT scans, and potentially risky tissue biopsies.

There’s a faster, more effective way, according to a paper from Cormac McCarthy, MD, PhD, Brenna Carey, PhD, and Bruce Trapnell, MD.

“Transformative, disease-specific, blood-based diagnostic tests for multiple PAP-causing diseases are now available for routine clinical use,” the co-authors state. “The serum GM-CSF autoantibody test is a validated test of known accuracy and precision that is highly sensitive and specific for autoimmune PAP, the most common PAP-causing disease, accounting for 90% of cases.”

Transbronchial and surgical lung biopsies are not useful in diagnosing any PAP-causing disease and both are associated with significant procedure-related morbidity, the co-authors say. Instead, diagnosis should begin with a serum GM-CSF autoantibody test. Then, as needed, other disease-specific, non-invasive serum, blood and genetic tests.

Lung biopsy should be reserved for patients in whom identification of the PAP cause remains uncertain after completion of these tests.

Diagnostic testing in patients with PAP syndrome.

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A photo of Cormac McCarthy, MD, PhD.

Cormac McCarthy, MD, PhD

A photo of Bruce Trapnell, MD.

Bruce Trapnell, MD


McCarthy C, Carey B, Trapnell BC. Blood Testing for Differential Diagnosis of Pulmonary Alveolar Proteinosis Syndrome. Chest. Feb 2019;155(2):450-452.