Your doctor may suspect pulmonary alveolar proteinosis (PAP) based upon your history of symptoms such as breathlessness with very slow onset and a physical examination revealing a crackling sound when listening with a stethoscope and when other, more common, causes of lung disease have been ruled out using other investigations such as a chest x-ray.
Often the physical examination is supported by a chest x-ray or CT scan. The chest x-ray in PAP typically reveals the presence of whitish, fluffy shadows scattered throughout both lungs. The CT scan images typically reveal extensive white patches within the lungs (ground glass opacity) with superimposed angular lines (reticular densities). The pattern that the images show is often referred to as “crazy paving” and is characteristic of PAP, but it is not sufficient to establish a diagnosis as it can be a sign of other diseases.
Some doctors use a specialized procedure called bronchoscopy to conduct a bronchoalveolar lavage (BAL). The BAL fluid is examined to see if PAP is present.
When you undergo a bronchoscopy the doctor passes a bronchoscope through your nose or mouth and through your windpipe into your lungs. A bronchoscope is a tube used to see the inside of the airways and lungs. The doctor sends a saline solution through the tube into the lung and then withdraws it again. This allows the doctor to collect samples of lung cells, fluids, and other materials inside the air sacs. This part of the procedure is called a lavage. The bronchoscope may also be used to collect a sample of lung tissue for examination (biopsy).
If the doctor suspects that the symptoms may be caused by PAP a specific and very sensitive blood test can be performed. The blood test can identify an increased presence or absence of GM-CSF autoantibodies, which is an indicator of autoimmune PAP. Similarly, a series of blood tests are being developed for the detection of hereditary PAP.
If the examinations mentioned above have not given any conclusive results about your diagnosis, the doctor may choose to perform a biopsy of the tissue in your lungs. The biopsy is a surgical procedure called open lung biopsy.
When an open lung biopsy is performed a general anaesthesia is used, which means you are asleep and pain-free during the procedure. A tube is placed through your mouth down your throat to help you breathe. While you are sedated the doctor removes a small piece of tissue from your lung, which then is examined.