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False-positive and false-negative results are all too frequent when patients with suspected pheochromocytoma are evaluated with plasma and 24-hour-urine catecholamine levels. This study from the UK examined the diagnostic accuracy of overnight urinary catecholamine excretion, the rationale being that catecholamine excretion during sleep would not be "contaminated" by sympathetic output from physical activity and emotional stimuli during the day.
The researchers measured overnight urinary catecholamines and metabolites in 16 patients with histologically proven pheochromocytoma and 190 controls (166 with hypertension and 24 with normal blood pressure). The range of overnight norepinephrine excretion in patients with pheochromocytoma (86 to 155…