Proper specimen collection and handling is an integral part of obtaining a valid and timely laboratory test result. Specimens must be obtained in the proper tubes or containers, correctly labeled, and then promptly transported to the laboratory.
Obtaining reliable and accurate laboratory test results
Physicians and others responsible for obtaining specimens and transporting them to the laboratory have a vital role in ensuring that laboratory test results are valid. The following are essential safeguards for your patients.
1. Avoid patient identification errors
Use at least two patient identifiers when administering medications, blood, or blood components.
Label containers used for blood and other specimens in the presence of the patient.
–Joint Commission National Patient Safety Goal 1, Elements of Performance, 2015.
Identify the patient prior to collecting a sample. Check armbands. Acceptable identifiers may include the patient’s full name, date of birth, or medical record number.
2. Draw the tubes in the proper sequence
When multiple tubes are to be drawn from a single venipuncture using an evacuated tube system (e.g. BD Vacutainer® or Greiner Vacuette®), there is a correct sequence for blood collection that prevents cross-contamination of tube additives that could cause erroneous test results. The following should be used for both plastic and glass blood collection tubes.
The order of draw:
- Blood culture
- Coagulation tube (blue top) (1)
- Serum tube with or without clot activator, with or without gel (red or gold top)
- Heparin tube with or without gel plasma separator (green top)
- EDTA (purple top, pink top)
- Oxalate and fluoride (gray top)
- Other special tubes
(1) All blue tops collected for coagulation assays which do not have a blood culture collected first must have a discard tube collected prior to filling. Discard tube should be another blue top in which greater than 1 mL of blood is collected.
All tubes must be gently inverted 10 times end-to-end immediately after collection.
3. Use proper containers for collection
Certain analyses require containers with preservatives and/or anticoagulants, while others do not. Using the wrong container often leads to erroneous results. See the test catalog for exact requirements.
4. Mix all tubes ten times by gentle inversion immediately after collection
5. Do not decant specimens from one type of container into another
Specimens must be submitted to the laboratory in the container used originally for collection.
6. Deliver specimens to the laboratory promptly
Valid measurement of analytes in serum or plasma requires prompt separation from the blood cells. When left unseparated, analytes shift between the cells and the plasma or serum and glucose is consumed. Some analytes are unstable at room temperature. Drawing extra tubes of blood on patients and holding them as a contingency against some unforeseen need for more tests can lead to erroneous results and is a dangerous practice that should be avoided.
For specimens drawn off campus
Red and gold top tubes must stand for 30 minutes to allow for complete clotting. They must then be centrifuged and the serum separated and refrigerated until delivered to the laboratory. Check specific test information in the manual to determine if serum should be frozen.
Purple top tubes for CBCs may be kept at room temperature for up to 8 hours. After 8 hours, refrigerate until delivery. Stable 36 hours refrigerated. For tests drawn in purple top tubes other than CBCs, please check specific test stability.
Green top tube handling depends on the specific test ordered. Check specific test directions.
Laboratory specimen storage temperature requirements
|Storage Method||Centigrade (Celsius) Temperature Range|
|Refrigerated||2 – 8 º C|
|Frozen||less than or equal to -20 º C|
|Room/ Ambient||20 – 25 º C|
7. Avoid hemolysis
Erythrocytes contain certain analytes (LD, AST, K, ALT) in concentration many times higher than in plasma. When red cells are hemolyzed, there is a release of these analytes and dilution of plasma, resulting in erroneous laboratory values. Also, hemolysis may interfere in analytical methodologies.
8. Drawing samples from a line
If the sample is to be drawn from a line, be sure to draw approximately 5-10 mL for adults in a first “flush” syringe (20 mL to clear any heparin from the line if coagulation tests are desired). Then draw the syringe for the desired tests. The “flush” may be given back to the patient if needed.