Hematocrit Determination In The I-Stat System; Edta And Kedta Customization For Hematocrit On The I-Stat System - Abbott i-STAT 1 System Manual

Hematocrit Determination in the i-STAT
Comparison To Other Methods
This bulletin describes the four most common methods for determining hematocrit (microhematocrit,
conductometric, and as calculated by automated cell counters and co-oximeters) and the common
interferences, which lead to discrepancies among the four methods.
The i-STAT System uses the conductivity method to determine hematocrit. The Point-of-Care Testing
Coordinator should ensure that end users are aware of factors affecting results obtained on the i-STAT
System. Factors affecting hematocrit results are included in this Technical Bulletin.
HEMATOCRIT
CLSI recommends that the term hematocrit be used to describe the materials and/or method used to
measure Packed Cell Volume (PCV).
by the red cells to the volume of whole blood in a sample of capillary, arterial or venous blood. This ratio is
measured after appropriate centrifugation and is formally expressed as a decimal fraction.
Abbott Point of Care Inc. has retained the term hematocrit for the measured quantity and, according to
common practice, expresses hematocrit as a percentage, in units of Percent Packed Cell Volume (%PCV). A
hematocrit of 0.45 PCV is expressed as 45 %PCV.
THE METHODS
The Microhematocrit Method
Microhematocrit is the standard method for hematocrit determination
microcapillary tube is spun in a centrifuge. The red blood cells are separated from the plasma by the
centrifugal force. The height of the separated red blood cell column is compared to the height of the entire
sample column to determine the packed cell fraction (i.e., the hematocrit).
The hematocrit of a sample can be altered by the anticoagulant. It is well documented that K
the cells to shrink by increasing the osmotic pressure in the plasma
below its value in-vivo. Current literature indicates that the hematocrit is reduced between 1.5 %PCV and
2.2 %PCV at normal hematocrit levels. Experiments conducted by Abbott Point of Care Inc. indicate a
shrinkage of about 2 %PCV at normal hematocrit levels. For more information, please see the Technical
Bulletin "K EDTA and K EDTA Customization for Hematocrit on the i-STAT System" (716240).
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i-STAT
TECHNICAL BULLETIN
PCV is defined as the measure of the ratio of the volume occupied
1
Art: 714261-01D
®
System and
®
. An anticoagulated sample in a
1
, thus reducing the hematocrit
1,2,3,4
EDTA causes
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Rev. Date: 10-Jan-11