Catecholamines are stable in urine IF the 24 hour pH is 5-6. Since this
will not be true of all individuals, storage without preservatives is only
reliable when there is a pH check. In practice, a pH check at the
collection site poses challenges.
The whole rationale for preservation is based upon this subset of
individuals with urine at pH 7-8. It is important to note that urine may
become basic as a result of drug therapies.
Steven R. Binder
Clinical Diagnostic Group
Bio-Rad Laboratories
____________________Reply Separator____________________
Subject: Catecholamines
Author: Clinical biochemistry discussion list
<[log in to unmask]>
Date: 3/19/2003 5:43 AM
The collection and preservation of urine and plasma samples for the
determination of catecholamines was summarized in an article by Boomsma et
al in Clin Chem 39:2503-2508, 1993.
In summary-
Plasma:
Centrifugation required within 1 hour of collection of EDTA blood sample
(no need for a refrigerated centrifuge).
Plasma catecholamines stability:
1 day at 20 C
2 days at 4 C
1 month at -20 C (or 6 months with added glutathione)
1 year at -70 C
Urine:
- Collection can be carried out without acid (catechols stable for up to 4
days)!
- Acidification is the best method for long-term preservation of urinary
catecholamines
- With EDTA and meta-bisulfite addition, catechols are stable at 4 C for
up
to one year
Preservatives can be added after the collection is complete.
We tried out these guidelines in a relatively small series of samples, and
our experience confirmed them.
Best wishes,
Oren Zinder
Department of Clinical Biochemistry and Laboratory Medicine
Rambam Medical Center
Haifa, ISRAEL
Prof. Oren Zinder
Department of Clinical Biochemistry
Rambam Medical Center
Haifa, ISRAEL 31096
Tel: +972-4-854-3767
Fax: +972-4-854-2409
email: [log in to unmask]
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