S001

The Utility of Urine Metanephrines and Urine Catecholamines in the diagnosis of Phaeochromocytoma and Paraganglioma.

Jasdeep Gill, Chung Thong Lim, Margaret Hancock, Susan E Brook, Tricia Tan

(Imperial College Healthcare NHS Trust)

Background: Phaeochromocytomas and paragangliomas are rare tumours derived from the sympathetic or parasympathetic paraganglia. They characteristically secrete catecholamines (noradrenaline/adrenaline/dopamine), which are metabolised to metanephrines (normetadrenaline/metadrenaline/3-methoxytyramine respectively). These tumour markers can be detected in 24-hour urine collections as first-line investigative tests.

Objectives: To evaluate the utility of urinary metanephrines compared to that of urinary catecholamines in diagnosing phaeochromocytomas and paragangliomas, and to optimise the existing diagnostic cut-offs at Imperial College Healthcare NHS Trust for both assays.

Design and setting: A retrospective study of 73 patients with known phaeochromocytoma or paraganglioma, from whom 194 urine catecholamines and 38 urine metanephrines were measured using high-pressure liquid chromatography. A control population of 135 hypertensives was used, from whom 219 urine catecholamine and metanephrine results were collected.

Results: Receiver-Operator Characteristic (ROC) curves were used to evaluate statistically the diagnostic performance of metanephrines, which performed similarly to catecholamines. Our current upper limits of normal (ULN) for the parameters, derived from another institution’s study, give diagnostic sensitivities (specificities) of 69.1% (90.9%) for combined urine catecholamines and 71.1% (84.9%) for combined urine metanephrines. Using the 95^th percentiles of the screened population as the proposed ULN, these change to 66% (93.6%) for combined urine catecholamines and 65.8% (91.8%) for combined urine metanephrines.

Conclusions:

Our urinary catecholamine and metanephrine assays perform similarly with the latter marginally more sensitive using the proposed ULN. High test specificities should be prioritised with tolerable sensitivities to decrease false-positive rates, as these represent the majority of misdiagnosed results when screening for a relatively rare condition.