The diagnosis of AL amyloidosis may be confirmed (or may be eliminated) by taking a tissue biopsy and performing an SAP scan, as described in the section of this website on diagnosis of amyloidosis.
Additional Investigations for AL Amyloidosis
Other tests that doctors may order in patients with suspected AL amyloidosis include:
- blood tests
- urine tests
- ECG (electrocardiogram)
- echocardiogram
- bone marrow biopsy
Blood tests
No blood test is diagnostic of AL amyloidosis but some test results can raise or support the suspicion.
Full blood count (FBC) – There are no specific findings in this test that can show whether or not AL amyloidosis is present. FBC is usually monitored during treatment, as some of the medications may cause abnormalities in the levels of red blood cells or white blood cells.
Serum protein electrophoresis (SPE)– This may show a paraprotein – abnormally high levels of one antibody or antibody fragment.
A paraprotein may be present in myeloma, in AL amyloidosis or in healthy people with a condition called monoclonal gammopathy of uncertain significance (MGUS). Patients who only have MGUS without disease symptoms often only require follow up by their doctors.
Detection of a paraprotein alone does not lead to a clear diagnosis. Doctors need to consider it in conjunction with all the symptoms, clinical findings on examination and results of all investigations before making a diagnosis.
Serum free light chains – This is a very sensitive test for measuring levels of free light chains in the blood. Raised free light chains may be present in myeloma, in AL amyloidosis or in healthy people with MGUS. Patients who only have MGUS without disease symptoms often only require follow up by their doctors.
Raised free light chains alone does not lead to a clear diagnosis. Doctors need to consider free light chain results in conjunction with all the symptoms, clinical findings on examination and results of all investigations before making a diagnosis.
Free light chain concentration is very useful for monitoring the response to treatment once AL amyloidosis has been diagnosed.
Kidney function tests – These tests can show how well the kidneys are functioning. Kidney function may be abnormal in AL amyloidosis, and in many other, commoner conditions. Abnormal kidney function is not a means of diagnosing AL amyloidosis. However, all patients with AL amyloidosis should have their kidney function regularly monitored.
Urine tests
Spot urine tests and 24 hour urine collections may detect raised levels of protein, which is a sign of abnormal kidney function. Kidney function may be abnormal in AL amyloidosis, and in many other, commoner conditions. Abnormal kidney function is not a means of diagnosing AL amyloidosis. However, all patients with AL amyloidosis should have their urine protein levels regularly monitored.
Urine tests may also detect a paraprotein or free light chains. This finding may be present in myeloma, in AL amyloidosis or in healthy people with MGUS. Patients who only have MGUS without disease symptoms often only require follow up by their doctors.
Urine paraprotein or raised free light chains alone does not lead to a clear diagnosis. Doctors need to consider these findings in conjunction with all the symptoms, clinical findings on examination and results of all investigations before making a diagnosis.
Electrocardiogram (ECG)
The ECG test is a safe, rapid, painless method whereby the electrical impulses in the heart can be detected, measured and represented as a tracing on graph paper. This tracing can then be analysed by doctors. The appearance of the various waves, dips and spikes on the tracing supply many different types of information about the size and functioning of the heart muscle.
Typical ECG of a patient with cardiac AL amyloidosis(from Updates in Cardiac Amyloidosis:A Review; Banypersad S et al; J Am Heart Assoc 2012)
All patients with suspected amyloidosis should have an ECG. Most patients referred to the NAC have already had this test done. If not, ECG can be performed at the NAC. The findings can be helpful in making the diagnosis. Some ECG appearances are suggestive of amyloidosis in the heart. This is especially true when the echocardiogram also shows particular findings. Progressive ECG changes may be useful in assessing silent progression of amyloid heart disease. After treatment of AL amyloidosis there is usually no change seen in the ECG, but in some cases changes may occur.
Echocardiogram
Echocardiography is a type of ultrasound test. In this type of test reflections of sound waves are used to build up a detailed picture of organs inside the body. It is safe and painless and does not involve any exposure to radiation. The ultrasound technician uses gel to improve skin contact on the chest with a piece of equipment called a transducer. The transducer aims sound waves in the direction of the heart and detects the waves that reflect (echo) back. The sound waves cannot be heard as they are high frequency, outside the audible range for our ears. The ultrasound machine detects the waves echoing back and converts them into a detailed picture of the heart, which the technician views on a screen like a television screen. Doctors who know how to interpret these pictures can obtain a wide variety of detailed information about the structure and functioning of the heart.
Echocardiogram from a patient with AL amyloidosis affecting the heart. (from Updates in Cardiac Amyloidosis:A Review; Banypersad S et al; J Am Heart Assoc 2012)
All patients with suspected amyloidosis should have an echocardiogram. When amyloidosis in the heart is advanced, it is usually clearly visible on the echocardiogram. However, the findings may be less clear at the early stages of amyloid heart disease. When amyloidosis affects the heart, the walls of the large heart chambers known as ventricles are evenly thickened. The heart appears stiffened. Although the heart muscle contracts normally, due to the stiffness it does not fully relax. This failure to relax properly is called “diastolic dysfunction”. It is usually the earliest abnormal finding to become apparent on echocardiography. There may be diastolic dysfunction before there are even any symptoms of heart disease. However, diastolic dysfunction is also commonly seen in other diseases, and is by no means diagnostic of amyloidosis.
Bone marrow biopsy
In this test, a small sample of bone marrow tissue is taken from a bone, usually at the hip. The doctor applies local anaesthetic to numb the skin first, and then inserts a needle to the back of the hip to remove the tissue sample. Some patients choose to be given a light sedative before the procedure. This causes sleepiness during the procedure itself, although the patient is still conscious and able to co-operate. Afterwards there is usually little or no memory of the procedure itself. Sedation may not be suitable for all patients with amyloidosis. The sample is then examined in the laboratory to determine whether there are abnormal plasma cells.
Cardiac Magnetic Resonance
Cardiac Magnetic Resonance (CMR) imaging is a method whereby a magnetic field and radio waves are used to obtain detailed pictures of the heart. It is safe and painless, and does not involve any exposure to radiation. Before the scan, contrast material may be injected into the patient’s vein. During the scan, patients lie still inside a closed “tunnel” type of scanner for up to one hour. The pictures produced by the computer can then be examined by doctors. In many ways the information provided by CMR is similar to that provided by echocardiography. However, in some patients, echocardiography may not be able to determine whether heart wall thickening is due to amyloidosis or to another cause such as hypertension. In such patients, CMR can help to distinguish between these different causes of heart wall thickening. When doctors analyse the CMR scans, they can often clearly visualise the amyloid deposits within the heart walls, between the heart cells. It is expected that in the future it may be possible to use CMR to accurately measure the size of the amyloid deposits within the heart wall. Such measurements could then be repeated to follow the build-up of amyloid deposits and their regression with treatment.