What tests can determine that I have Carcinoid/NETs
There are a wide variety of tests available. Some range from rather non-invasive, such as a urine test, to surgical exploration.
Many, but not all, Carcinoids/NETs secrete Serotonin. This can be measured with a 24 hour urine test called a 5-HIAA. This test measures the metabolite (used up portion) of the Serotonin. There are specific foods you should avoid prior to the test, and not all centers will tell you about the. Some require the jug of urine to be refrigerated during the collection. This is the same Serotonin that you hear bout in people with depression, but they do different things in the body and it does not cross the blood/brain barrier.
Serotonin can also be measured by blood, but blood tests for it do have their drawbacks. When tested properly, urine or blood are both fully acceptable. Some of the problem is in the way that the blood samples are handled. Normally the blood is taken is a red topped tube, which has no chemical additives. Medical staff can be creatures of habit, and some bad habits. Since most of the blood test tubes they use have an additive, they get into the habit of mixing the blood in the tube. This is supposed to be done by rocking the tube back & forth a few times. But, how many times have you seen them shake the tube rapidly? Doing so can cause the red blood cells to rupture (hemolysis) and thus causing the tests results to be abnormally high because it releases the hormone captured in the cells.
Some tumors can be more predictable for what hormones are likely to be found elevated. The most common “markers” are (in no specific order):
Chromogranin A, Pancreastatin, Neuron Specific Enolase, Substance P, Histamines, 5HIAA, Pancreatic Polypeptide, Atrial Naturetic Hormone, gastrin, VIP, Calcitonin, CEA, Insulin, Glucagon, Alpha/Beta subunits of HCG and ACTH. Not all doctors will test for all of these.
According to Dr. Richard Warner, blood “markers” are easier to test and will show changes in tumor load well before imaging tests and symptoms changes.
Taking a careful history of symptoms can lead toward a diagnosis, but some symptoms are often confused with more common ailments. Also, many patients do not associate some of the symptoms as being relevant, so it goes unmentioned. For example, when searching for a reason for abdominal pain, most people would not know to mention that they have facial flushing from time to time, yet the two are connected. About 1/3 of all patients have absolutely no symptoms at all.
Carcinoid/NETs do not release their excess hormones on any specific schedule. This can lead to confusion is diagnosis, sometimes tracking things like foods to determine a cause becomes frustrating. There are some specific things that may cause a Carcinoid event. Each person may have different “triggers”, the most common of which is that huge meal (think Thanksgiving dinner), while for some it can be alcohol (red wine especially), stress, excess exercise and even some drugs, like epinephrine.
Keep in mind that any test, blood, urine, even tissue sample is merely a snapshot of that particular segment, at that particular time it was taken. When watching markers, watch for trends, not individual numbers. Tests can be done wrong, can be artificially elevated, or even the wrong sample. One test is not a trend.
It is also important when talking about results to know what the “normal” range is for that particular laboratory doing the test. They vary widely and cannot be calculated from one to another. For that reason, it is recommended that whatever lab you use, stay with that one.
If biopsied tissue is taken, it can be stained for Chromogranin A, Synaptophysin, and others. It can also have a “rate of proliferation” test done (Ki-67) to see how fast that tumor is growing and help project how fast it may continue to grow.
Then there are imaging tests.
Let’s look at how imaging generally works. They scan (CT, MRI, etc) the area. They then look at the resulting “pictures” for differences in tissue from the adjoining normal tissue. If the difference in tissue is not that dramatic, the anomaly can be disregarded and called “unremarkable”. One of the problems with Carcinoid/NETs is that they can be fairly close to normal tissue and easy to miss, especially the primary tumor which remains small.
CT and MRI have a place is showing tumors, but they are usually done as part of a fusion scan with (or after) and Octreoscan. The Octreoscan is a specialized test for Carcinoid/NETs. It can NOT show the size of the tumors, just give the possible locations which can then be examined more closely with other scans.
PET scans are generally not of much use for Carcinoids/NETs as the tumors are slower growing and do not use as much sugar a common cancers, but are too close the regular tissue to show up well.