Best initial test for pheochromocytoma

[SlaveOfTCMC]

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First Aid says go straight to the 24 hour urine metanephrine collection

A USMLERx question supports this


Conrad Fischer says the BEST INITIAL TEST is a plasma metanephrine level (citing it is most sensitive)

But that the 24 hour urine collection is a confirmatory test.


From an outpatient care perspective, it would make more sense to obtain a plasma metanephrine level first, because it is far easier than forcing an inpatient and then collecting urine out of a Foley meticulously.


Thoughts?

 

[PokerDoc]

With due respect to Dr. Fischer, he's way off here. The problem with Plasma metanephrines is that the high sensitivity comes with the trade off of low specificity.

It's a really good test in a patient with MEN, since theyre high risk. But in a previously healthy person, it's not a great test because you're going to have to confirm with urine anyway.


I don't remember but i think the sensitivity of plasma mets were like 99% and specificity was like 80-85%. And then the urine test was 98% and 98% respectively. So to say plasma is more sensitive isn't very statistically significant.

I'd venture to guess Step 2 wants a urine test.

 

[SlaveOfTCMC]

I found this on emedicine:

yes it comes down to clinical suspicion

High-risk patients, including those who have a genetic syndrome that predisposes them to pheochromocytoma (eg, MEN 2A or 2B, VHL disease or neurofibromatosis, a prior history of a pheochromocytoma, a family history of a pheochromocytoma), should be screened with plasma metanephrine testing. In these scenarios, a higher-sensitivity test that lacks specificity is justified.[13]



A fractionated plasma free metanephrine level may be measured in a standard venipuncture sample taken from a seated, ambulatory patient.
Patients at lower risk for a pheochromocytoma, including those with flushing spells, poorly controlled hypertension, or adrenal incidentalomas with an adrenocortical appearance, should be screened with a 24-hour urine collection for catecholamines and metanephrines. This test has a high specificity and acceptable sensitivity.

 

[PokerDoc]

yay i remembered something!

 

[DoctorMY]

nice, makes a lot of sense. But sometimes the picture is so classic! do you still go for the 24 hr as initial test? hard to believe anybody would... oh well. better go by the guidelines and not invent our own medicine 😀

 

[OveractiveBrain]

nice, makes a lot of sense. But sometimes the picture is so classic! do you still go for the 24 hr as initial test? hard to believe anybody would... oh well. better go by the guidelines and not invent our own medicine 😀

Pheo
Patient: "spells" = Paroxysms of Palpitations (tachy), Pain (headache), Pressure (HTN), and Perspirations (sweating)
Dx:
- 1st: Urinary Metanephrines and VMAs (you wont have to choose between these, one is better, one is cheaper)
- Best: Pathology ("Biopsy" = Surgical Resection)
- Extra tests: Plasma levels, clonidine suppression test,
Tx: Alpha Blockade --> Beta-Blockade --> Surgery

Super Extra: If pheo, go looking for Thyroid Cancer (ultrasound) and Hyperparathyroidism (PTH, Ca, Phos, Calcitonin) for MEN2A. You won't do this on the test either, thats too advanced (endocrine boards)

 

[PokerDoc]

Ah yes, we still forget the $$$$ argument as med students. Cheaper is definitely a plus too!