Background: Pheochromocytoma is a rare adrenaline-producing tumour that arises from adrenal gland. The number of cases are increasing globally each year. Pheochrmocytomas release a hormone called adrenaline which can cause severe health problems such as hypertension (high blood pressure), heart attack, and stroke.  They might lead to death if not diagnosed early. Diagnosis of pheochromocytomas can be performed by different biochemical tests like catecholamines, metanephrines, chromogranin A …etc.

Objective: To determine the efficacy of plasma free metanephrines measurements for inclusion and confirmation of pheochromocytoma.

Methods: Multiple electronic searches were carried out to determine studies in the English-language. Databases used for this purpose were CINHAL, AMED, MEDLINE, PubMed, ScienceDirect, Google scholar and the Cochrane library. To identify relevant articles, various key terms were used. The articles obtained were published during or after 2005. Moreover, inclusion and exclusion criteria were applied while performing this search. The intervention was plasma free metanephrines and comparison with other biochemical test such as plasma or urinary catecholamines, urinary metanephrines, chromogranin A and deconjugated plasma metanephrines.

Results: From forty-four studies, only seven studies corresponded with inclusion and exclusion criteria. The main results of four studies showed that plasma free metanephrines were highly efficient in the diagnosis of pheochrmocytoma compared to   plasma catecholamines, epinephrines, urine metanephrines and plasma deconjugated metanephrines. The remaining three studies were displayed totally different findings. Urinary metanephrine, chromogranin A and urinary catecholamines demonstrated high sensitivities and specificities compared to plasma free metanephrines. Certain procedures like fast, abstinence from drugs; supine position should be followed by participants before and during blood and urine collection.

Conclusion: Plasma free metanephrines measurements are preferable (superior) in the diagnosis of pheochromocytoma. However, patients need to fast, abstinence from drugs, avoid caffeinated and decaffeinated beverages and blood should be collected in the supine position.

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Dr Hassan Sadek

Senior Consultant Lecturer, Oman College of Heath Sciences, Ministry of Health, Oman