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Please review the
following guidelines prior to collecting specimens:
GENERAL
-
Avoid patient identification errors. Identify the patient prior
to collecting a sample. Check identification bands.
-
Draw the tubes in proper sequence.
When multiple tubes are
being drawn using the Vacutainer® or similar system, there is
a recommended order of draw:
-
Blood culture tube
-
Nonadditive tube
(e.g., red stopper)
-
Coagulation tube (e.g.,
blue stopper)
-
Other additive tube
(e.g., green stopper)
-
In addition, all tubes
containing an anticoagulant or additive (i.e. all tubes other than red
top tubes) must be quickly but gently inverted 3-4 times to mix.
-
Use proper containers for collection and storage. Each test entry in this
manual contains collection container information. Using the wrong
container often leads to erroneous results. Do not freeze specimens in
glass tubes. Always use plastic containers.
-
Avoid hemolysis. Erythrocytes contain certain
analytes in concentrations many times higher than in the plasma. When
red cells are hemolyzed, there is a release of these analytes. Also,
hemolysis may interfere in analytical methodologies.
COAGULATION SPECIMENS
- Obtain
venous blood by clean venipuncture. Avoid slow flowing draws and/or
traumatic venipunctures as either of these may result in an activated or
clotted sample. Do not use needles smaller than 23 gauge.
- If only a
blue top coagulation tube is to be drawn, a discard tube other than the
blue tube should be drawn first to eliminate possible thromboplastin
contamination from the site of the venipuncture.
- Use 3.2 %
citrate tubes for coagulation studies.
- Fill
light blue top tubes as far as vacuum will allow, an exact ratio of 9
parts blood to 1 part anticoagulant must be maintained, and mix by
gentle inversion.
-
Immediately centrifuge the specimen as directed under individual assays.
- Hemolyzed samples should not be used because of possible
clotting factor activation and end point interference. In most cases,
hemolyzed specimens will be rejected.
- The
volume of citrate in blue top tubes must be adjusted for patients who
have hematocrit values above 55%. See chart below or call Client
Services at 1-800-967-9672 or 412-209-7270 for assistance.
Hematocrit Correction Table
|
Patient’s
Hematocrit (%) |
Volume of Citrate
for
5 mL total
volume
anticoagulated blood |
Volume of citrate to remove from 5
mL vacuum tube |
|
55 |
0.42 mL |
0.08 mL |
|
60 |
0.37 mL |
0.13 mL |
|
65 |
0.33 mL |
0.17 mL |
|
70 |
0.29 mL |
0.21 mL |
|
75 |
0.24 mL |
0.26 mL |
|
80 |
0.19 mL |
0.31 mL |
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