Optimal collection and storage conditions for catecholamine measurements in human plasma and urine

Improvements in methodologies for measuring concentrations of catecholamines (CA) have led to an increasing use of these compounds as markers in the screening of patients and in long-term clinical trials. Because of the associated logistical problems, we have investigated the unresolved question of optimal conditions for sample preparation and for storage of plasma and urine samples. Results show that blood should be centrifuged within 1 h after collection; the use of a refrigerated centrifuge is not necessary. Once plasma is prepared, CA are stable for 1 day at 20 degrees C, 2 days at 4 degrees C, 1 month at -20 degrees C (or 6 months with added glutathione), and up to 1 year at -70 degrees C. CA are stable at 4 degrees C for 1 month in unpreserved urine and for 4 months in urine preserved with EDTA and sodium metabisulfite. In acidified urine, CA were nearly unchanged after 1 year at 4 and -20 degrees C.