Once pheochromocytoma is suspected in a given patient, biochemical tests need to be done first. A common mistake is doing an abdominal imaging test before biochemical tests are done. Imaging tests should only be done after biochemical tests highly suggest pheochromocytoma.
There are actually a few issues with biochemical tests that can make the test selection and test result interpretation rather complicated. There are 5 biochemical tests for pheochromocytoma: 2 measure chemicals in the blood, 3 measure chemicals in the urine. The 2 blood tests are called "plasma catecholamines" and "plasma fractionated metanephrines". The 3 urine tests are called "24-hour urine catecholamines", "24-hour urine metanephrines", and "24-hour Vanillylmandelic acid (VMA)". Another blood test called "chromogranin A (CGA)" may be occasionally used but this test is secondary to the other 5 tests.
So which test or tests to use? There are no clear or definitive answers to this question. A doctor has to take several issues into consideration. Usually only specialists like Dr. Pheo myself knows most of the nuts and bolts of all those tests but even specialists sometimes do not know what the best test is. In an ideal situation, "plasma fractionated metenephrines" are the test Dr. Pheo prefers for a variety of reasons. For a certain patient in certain situation, any one of the 5 tests can be the best test.
Now the results are back. What do they mean? Test results should not be simply labeled as "normal" or "abnormal". The extent of elevation of the results compared with normal reference range is very important. Test results are also open to interference by medications, diseases, and human errors. So if you have a test result that is only 20% above the normal range, don't panic. Chances are you don't have pheochromocytoma. On the other hand, a 20% increase may indicate pheochromocytoma in other people. Really tricky, isn't it? Although Dr. Pheo myself is very comfortable in interpreting test results for most patients, Dr. Pheo at times has to ponder on some results for days before making a call.
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I thought I had posted a comment, but I don't see it now. My question concerns the SDHB gene. My son has had two tumors removed this year and has the gene.. How often should he have the biomedical tests done? I have heard every 4 months and have heard once a year. What do you think? Thank you.
ReplyDeleteI answered under your comment on "what is pheochromocytoma".
ReplyDeleteDr pheo,
ReplyDeleteThank you for your time on this site and info.
I have a few questions,
1. What is average turn around on 24 hour urine test in your lab?
2. Do you encounter pheo patients with volume issues? i.e. polydipsia/polyuria (4500ml/24hour)
thank you again
This comment has been removed by the author.
ReplyDeletealohagreen,
ReplyDelete1. 8-10 days.
2. The larger the urine volume, the higher the absosulte values. Correction by urine creatinine should help.
Dr. Pheo
Thank you for the quick response.
ReplyDeleteI do see children commonly associated with polydipsia/polyuria and pheo. Is this uncommon in adults? Have you ever heard or seen this in any of your patients?
Perhaps another endocrine issue with similar symptoms will be investigated. Will keep posted for closure.
Thank you again for your educational information.
Polydipsia/polyuria are indeed more common in children than in adults. They are rather rare in adults.
ReplyDeleteDr. Pheo
I have MEN2a, thyroidectomy, partial para thyroidectomy, and have been monitored for a pheo for the past 14 years. 6 months ago my plasma metanephrines cw back borderline elevated, 24 hr urine confirmed that. My endo repeated plasma last week, they are still borderline elevated, slightly more so than 6 months ago. About 1.5x the upper limit....so not a definitive pheo by any means. Would you continue just repeat testing? Do an ultrasound at this point? Or could it just be stress causing this?
ReplyDeletePlease see my response under the latest post.
DeleteHello Dr Pheo,
ReplyDeleteI have a couple of questions about urine and plasma testing my symptoms started 4 weeks ago with a very severe episode of BP 220/125, lightheaded, dizzy, chest pressure, numb hands. A head CT and EKG done, all normal. Sent home and I presumed it was a weird fluke and I'd never know what happened. The past 4 weeks since, I've had 4 more episodes although not as bad as the first. But one of them warranted a second ER visit....the other two, I stayed at home and rode it out. I was fitted yesterday with a 24 hour cardiac monitor for 30 days and have a 24 hr urine collection to do. My question is, I had a mild episode tonight, chest tightness, tachycardia, BP high but only to 170/107 for a short time. Is it better to wait one the urine test and collect it during a severe episode to ensure more accuracy?
Strange thing though....my cardiac monitor beeped at me and told me to call it in...I didn't because I don't have a land line....but it was about 30 seconds after my cardiac alarm that my symptoms started. If I do have a pheochromocytoma, is it possible that the first adrenine surge of this episode could cause an arrythmia? I'm 47, active and otherwise extremely healthy. Thank you for your time and expertise.
Hello Dr Pheo,
ReplyDeleteI have a couple of questions about urine and plasma testing my symptoms started 4 weeks ago with a very severe episode of BP 220/125, lightheaded, dizzy, chest pressure, numb hands. A head CT and EKG done, all normal. Sent home and I presumed it was a weird fluke and I'd never know what happened. The past 4 weeks since, I've had 4 more episodes although not as bad as the first. But one of them warranted a second ER visit....the other two, I stayed at home and rode it out. I was fitted yesterday with a 24 hour cardiac monitor for 30 days and have a 24 hr urine collection to do. My question is, I had a mild episode tonight, chest tightness, tachycardia, BP high but only to 170/107 for a short time. Is it better to wait one the urine test and collect it during a severe episode to ensure more accuracy?
Strange thing though....my cardiac monitor beeped at me and told me to call it in...I didn't because I don't have a land line....but it was about 30 seconds after my cardiac alarm that my symptoms started. If I do have a pheochromocytoma, is it possible that the first adrenine surge of this episode could cause an arrythmia? I'm 47, active and otherwise extremely healthy. Thank you for your time and expertise.
Dear Charlotte,
DeleteIf you have a pheo, the urine metanephrines levels should be abnormally high on every day. The levels are indeed even higher if you have an episode. It usually does not matter whether you have an episode to collect the urine.
You could have arrhythmia first then symptoms.
Dr. Pheo