Types of Specimens
Cultures…to name a few
Represents blood as it circulates through the body
Contains erythrocytes, leukocytes, and platelets
Uses: CBC, Blood Bank, Flow cytometry, BNP, Hemoglobin A1c
One type of liquid portion of the blood
HAS NOT CLOTTED!
Contains fibrinogen, and clotting factors
Uses: PT, APTT, Fibrinogen, Dimer
Liquid portion of the blood
Sodium or lithium heparin
Has not clotted!
Uses: Rapid chemistry ie, glucose, electrolytes
Tube has been allowed to clot before centrifugation
No clotting factors or fibrinogen present
Liquid portion of the blood
Contains proteins, enzymes, organic and inorganic chemicals and antibodies
Uses: Chemistry, Therapeutic drug levels, Immunology, Blood Bank
Has no additive
Same analytes as before
Gel: activates clot and acts as a barrier
Popular for ease of use
Not suitable for TDMs
Not recommended for Transfusion testing
Why is Phlebotomy Important?
“The quality of any test result
is only as good as the
specimen that is tested!”
We can monitor testing personnel through competency testing…We can monitor instruments and procedures by means of calibrations and controls…BUT, we can’t monitor specimen collection very well!!
Specimens must be drawn in the correct tube and they must be filled to the proper level
Timely delivery to laboratory is critical
Anticoagulant additives can contaminate subsequent tubes
Some additives change the shape or size of the cells
Additives can give falsely elevated results
Proper specimen labeling is essential
Correct patient identification:
Two forms of identification is best….birthdate, medical record number, full name
Patient preparation…fasted, dose time, medications, transfusion status
Time of collection
Clotted specimens collected with anticoagulant
IV fluid contamination in specimens…Never collect above an IV line!
Must always be properly labeled
Must be collected in a sterile container
Volume of collection is critical to the test
Transport to lab must be timely
If held, storage requirements must be met
General Guidelines to Phlebotomy
The vast majority of medical tests performed in the clinical laboratory rely on a properly drawn tube of venous blood, with the most common site of the venipuncture being the veins in the antecubital space, which is where the arms bends at the elbow. The tourniquet is applied approximately 3 inches above the elbow and should be tight enough to compress the vein but not the artery. The patient is then asked to make a fist, and this clenching action serves to pump blood into the vein as blood is carried from the hand back to the heart. At this point, after cleaning the site with an alcohol pad, the needle is inserted into the vein and once blood is flowing freely into the tube, the patient is asked to relax the hand. The tourniquet must be released before withdrawing the needle to avoid bleeding at the site and hematoma formation.
It is important that the tourniquet not be left on for more than a few minutes (some sources quote 1 minute as the maximum allowable time) as this leads to concentration of some analytes, and the laboratory report for some substances will be falsely elevated. Another potential problem is hemolysis which, by rupturing the red cells, releases substances such as potassium, will also give rise to erroneous levels when testing. Steps to avoid hemolysis include making sure that the alcohol used to clean the phlebotomy site dries before venipuncture, using an appropriate needle gauge as small needles will cause hemolysis, avoiding blood draws from the area of a hematoma, and mixing blood-filled anticoagulant tubes by gently inverting several times rather than shaking.
For those patients with intravenous (IV) therapy, improper blood collection can lead to contamination of the specimen with IV fluids and markedly erroneous test results, either too high or too low depending on the substance and the composition of the IV fluid. For these patients, the blood must be drawn below the IV site. If this is not possible, the infusion must be stopped for at least 2 minutes with the first 5 mL of blood discarded before the blood to be tested is collected.
The proper ratio of blood to anticoagulant is especially important for coagulation testing. These tubes must be filled until the vacuum is exhausted and no more blood flows into the tube. Some substances deteriorate rapidly unless the blood is chilled—these tubes need to be immediately placed on a solution of crushed ice and water that was prepared prior to the phlebotomy. Some tests require a fasting specimen and, in these instances, it should be confirmed with the patient that he or she has had nothing to eat or drink, except water, for the previous 8 to 12 hours.
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