What tests are used to diagnose amyloidosis?

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What tests are used to diagnose amyloidosis?

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The most important thing by far is to think about it. So if we don't think about it, we're not going to do the test looking for it.

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So anyone who has

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any of the symptoms that I mentioned earlier, we need to think about amyloidosis. And then depending on the symptoms that they're having or whatever, tips us off as clinicians to think that a person may have amyloidosis, that really drives the testing algorithm.

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And so it could be, for example, if somebody has had urine testing and they have a lot of protein in the urine, then there's a workup for that.

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Or if they have new onset heart failure. So shortness of breath, leg swelling, then the first test is typically echocardiogram.

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once we figure that out, then we figure out which organs are most likely impacted by amyloidosis.

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then the next step is to try to identify it and see where it is or if we can find it.

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so often for people that have light chain amyloidosis. So typically they have those myeloma type proteins in the blood, so they have an M spike or they have light chains. A first step is usually a bone marrow biopsy. And so when we do the bone marrow biopsy, we can do the Congo red stain, and that's present in about 50% of patients with amyloidosis.

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So about half meaning of people who have amyloidosis of the light chain variety, we can pick it up in about half of them having bone marrow biopsies.

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If that doesn't work, then another thing that we can often do is what's called a fat pad aspirate. So fat pad aspirate, basically the idea is that

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for some people that have amyloidosis, that protein, that abnormal protein deposits in the fat under the skin, and so you can insert a small needle, suck out some of that fat, and then the pathologist runs the Congo red stain to look for the amyloidosis

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a reported sensitivity of that test.

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And the literature is about 50%. So again, means that you'll you'll pick it up in about half of patients if they have amyloidosis by doing the fat pad test.

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In a lot of places, the sensitivity is really not that great, meaning that places will often miss it due to technical problems or problems with the stain. So that test is a little bit more fraught than the bone marrow biopsy,

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but we'll often do those tests and then if they're negative and the clinical suspicion is high enough, then typically we're talking about organ biopsy.

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So again, it gets back to what you think the organs are involved are. If it's heart failure, then we sometimes do endomyocardial or heart biopsies, basically,

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for someone who has suspected kidney involvement, we'll do a kidney biopsy

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so you can do biopsies of different organs to basically find it do that Congo red stain.

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then the step beyond that is to do what's called amyloid sub typing in that the Congo red stain just shows amyloidosis.

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It doesn't tell you what kind. And we've talked about the fact that there are many different types of amyloidosis light chain TTR, many other ones, and it's really critical to nail down the subtype to avoid having patients treated for the wrong type. And the way that we do that is that there are sometimes things that pathologists can do, but most often it requires a test called mass spectrometry, which is a test that's run typically at Mayo Clinic.

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And so most labs send the samples out to the Mayo Clinic. The Mayo Clinic then runs the test. And basically I think of this almost like it's a test that if you think about a cake, it's a it's a technique that can take the cake apart and tell you what the ingredients are. So what this test does is it takes that chunk of amyloid tissue and basically chops up the protein, and then it tells you what that protein is made out of.

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And based on the sequence of all the amino acids, there are different protein components. They can look at that and say that this is light chain Lambda amyloidosis or Kappa amyloidosis or TTR amyloidosis or some other type. So that mass spec test is often quite critical for accurately diagnosing amyloidosis and more specifically, the subtypes.

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Is there a test to confirm if you have amyloidosis?

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amyloidosis is generally diagnosed by means of a biopsy,

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a test one might read about is a fat pad aspirate, which basically involves sucking out a tiny amount of fat from the skin, from under the skin, on the abdomen.

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The sample that we are talking about is about the size of a chickpea

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and a special stain called Congo. Red staining is done on that sample,

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a lot of times it's not necessary to do that specific test because there's already tissue available, for instance, a bone marrow biopsy. So if a patient if if a patient has a bone marrow biopsy already in the pathology department, it's possible to do that same Congo red standing on the bone marrow biopsy

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when amyloidosis is present.

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The combination of a bone marrow doing that testing on the combination of a bone marrow biopsy and a fat aspirate has about a 90% sensitivity for picking up amyloid. So that's pretty good testing.

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The other kind of testing that might suggest amyloid without definitively diagnosing it as cardiac imaging

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echocardiograms typically show thickening of the

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wall between the bottom chambers of the heart

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may show what we call a speckled pattern, which means that there is there is protein infiltrating the heart wall, and that has a certain appearance on the echocardiogram, the echocardiogram.

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They also show that the

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the heart is stiffer than usual,

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that's not necessarily specific for amyloidosis,

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just suggestive. And if those findings are present, it tells us that additional testing needs to be done

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one heart, one type of heart imaging that is a little bit more specific is an MRI with gadolinium.

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This shows a characteristic enhancement pattern that's pretty specific for amyloidosis and so that that can help secure a diagnosis of cardiac involvement.

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Should monitoring of amyloidosis be done on a regular basis?

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I think it's always important when a patient's being evaluated for multiple myeloma to ask about symptoms which suggest the possibility of concurrent amyloid

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or

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to make sure that you're not giving somebody a diagnosis of multiple myeloma when in fact what they have is al amyloidosis.

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by and large,

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most myeloma patients never develop amyloid. And

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in myeloma patients who ultimately develop it, it's not something that develops explosively.

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there isn't really

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special ongoing monitoring on a month to month basis for amyloidosis. Beyond the way myeloma patients are typically monitored. It's it's simply that if if suggestive symptoms develop over the course of monitoring the myeloma,

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that the possibility of amyloid is considered.