We have routinely used the Becton-Dickinson gel barrier tubes (SST gel and
clot activator) for collecting samples for serum ionized calcium for several
years. We have observed no stability problems with samples collected in
these tubes. This topic is addressed explicitly in the NCCLS Guideline
C31-A, "Ionized Calcium Determinations: Precollection Variables, Specimen
Choice, Collection and Handling; Approved Guideline". This document
references a study by Toffaletti et al (Clin Chem 1984;30:353-6) which found
no change in measured Ca++, pH, and pH-adjusted Ca++ in serum stored for 6
hours at 4 degrees C in either centrifuged (unopened) SST tubes or plain
red-top tubes. A companion study showed little change (mean change = -0.002
mmol/L) in pH-adjusted Ca++ at seventy (70) hours in unopened, centrifuged
SST tubes.
Salvador F. Sena, PhD, DABCC
Danbury Hospital
Danbury, CT 06810
USA
----------
From: [log in to unmask]
To: [log in to unmask]
Subject: Samples for ionised calcium
Date: Wednesday, March 17, 1999 12:12PM
Our samples for ionised calciums go to our neighbouring hospital and we
would
like to move away from whole blood to serum samples to give us more time.
Does
anyone have experience of using vacutainer tubes with gel (? manufacturer)
for
this purpose? Do you transfer the serum after centrifugation? Can you avoid
having to equilibrate with CO2/air? Do you check the pH at the same time?
Any
practical suggestions?
Thanks
Marieke Jordaan
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|