by Dr. Bruce Trapnell
You may suffer from autoimmune pulmonary alveolar proteinosis, or aPAP, but you might not know it yet. Importantly, your doctor may not know it either.
Thousands of Americans suffer from aPAP, a rare autoimmune lung disease caused by the progressive build-up of an oily substance normally present in the lungs called surfactant. In healthy people, surfactant forms a thin layer that lines the tiny air sacs (alveoli) of the lungs and helps them function while we breath. In people with aPAP, the surfactant over-accumulates, making the layer thicker in some air sacs and filling others, blocking oxygen from moving out of the air sacs and into the bloodstream.
Most patients with aPAP suffer from a feeling of breathlessness that worsens over time (doctors call this progressive dyspnea). Other common symptoms include cough, fatigue, chest congestion or pain, and weight loss. Less commonly, serious infections or lung scarring (fibrosis) can occur in patients with aPAP.
For many patients, the accurate diagnosis of aPAP is an arduous journey. Typically, a patient experiencing breathlessness will initially undergo a chest x-ray and if found to be abnormal, also a chest CT scan. While these tests can determine that a lung abnormality is present, neither can identify aPAP specifically. This is because the same test results – a cloudy appearance of the lungs – can be seen in other diseases (for example, pneumonia – a far more common problem than aPAP).
Consequently, aPAP patients are often misdiagnosed as having pneumonia and are prescribed antibiotic therapy that does not improve their condition and delays an accurate diagnosis, sometimes by years. Subsequent evaluations involve additional tests and procedures, for example, lung biopsies, which are costly, invasive and, unfortunately, unable to diagnose aPAP. Thus, historically, the timely and accurate diagnosis of aPAP has been difficult because it occurs rarely (in 1 out of every 150,000 people), symptoms are non-specific, common test results are non-specific, and many in the general public and medical community are unfamiliar with aPAP.
Thankfully, there is a better path forward – though it’s not sufficiently well-known. Our clinical research group published a report in 2019 and another report in 2022 describing a simple, noninvasive blood test – the Serum GM-CSF Autoantibody Test – that is highly accurate in diagnosing aPAP and is now commercially available to practicing physicians. The extraordinary accuracy of this blood test is because a high level of the antibody in the blood (an abnormal test result) only occurs in patients with aPAP, while people without aPAP have a very low level of the antibody (a normal test result). So now, knowing whether or not you have aPAP is as simple as getting a blood sample drawn, just as you would do to check your cholesterol.
Because aPAP is rare, few doctors in the United States are experienced in its diagnosis and treatment. However, the Serum GM-CSF Autoantibody blood test is available for routine clinical use by any physician in the country. Once the blood is collected, samples can be sent to one of only two testing locations in the country: Cincinnati Children’s Hospital in Cincinnati, Ohio, or National Jewish Health in Denver, Colorado.
With this blood test now available, the challenge is no longer an inability to diagnose patients in a timely and non-invasive way. The real challenge is making sure that the public and their doctors are aware of aPAP and the broad availability of this test to the medical community.
Given this challenge, a new resource, called the aPAP Awareness Initiative, has been created to benefit those living with aPAP, those wishing to learn more, and even clinicians and others in the medical community. Reaching a larger community means positively impacting the health and wellbeing of potentially thousands of undiagnosed patients. When patients have a precise diagnosis, they are more knowledgeable, feel more comfortable and in control of the problem, and need fewer procedures, which not only saves time and money but also limits uncomfortable visits to the hospital.
The sooner a patient understands the specific nature of their disease, the sooner they can begin receiving effective treatment and regain control of their overall health. This blood-based diagnostic allows patients living with aPAP to do exactly that.
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Dr. Bruce Trapnell is the director of the Translational Pulmonary Science Center and a professor of pediatrics at the University of Cincinnati.