Diagnosis of Amyloidosis
The diagnosis of amyloidosis is often delayed because the symptoms are so varied. Patients often get treated for heart or kidney failure for months before the underlying root of the problem is identified, typically by a biopsy.
Blood and urine tests may reveal an abnormal immunoglobulin protein in the body in those patients with AL Amyloidosis, but the only way to diagnose amyloidosis for certain is to take a sample of tissue for analysis under a microscope. Tissue is often taken from the fat around the abdomen which can be done on an outpatient basis in patients suspected as having the condition. This fat aspiration test will show a confirmatory positive result in 80% of patients with amyloidosis. Alternatively, a biopsy of the organ that is not functioning properly such as the heart, kidney or nerve can more reliably identify the condition but can be more cumbersome to obtain. This method of identification is becoming more common in our experience and often leads to the diagnosis in patients not suspected of the condition beforehand. A biopsy of the bone marrow is another useful method of detection and is critical to perform in patients suspected as having AL amyloidosis since it can identify and quantify the bone marrow lymphocytes or plasma cells which typically live there and are causing the problem. All of the above samples are stained with a dye called Congo Red that reacts with amyloid which can then be identified under a microscope.
It is critical to characterize the nature of the amyloid protein that is present since each of the various types of amyloidosis (such as AL, ATTR, or AA) is treated quite differently. Mass spectroscopy is a special technique that can be used on tissue samples to reliably determine the type of protein present. Blood samples can be used to sequence the various genes such as transthyretin or fibrinogen to determine if a predisposing gene variant exists. For patients with AL Amyloidosis, the free light chain assay is extremely useful to monitor the response to treatment. Patients suspected of heart involvement can get a cardiac MRI which can typically demonstrate findings suggestive of amyloidosis in those patients afflicted. All of these tests are available at Cedars-Sinai.