SPECIMEN COLLECTION PROCEDURES
Proper specimen procurement and handling is an integral part of obtaining a valid and timely laboratory test result. Accordingly, specimens must be collected in the proper tubes and containers, correctly labeled, and promptly transported to the laboratory. Any patient preparation that is required may be found in the Interpretive section of the individual test listings. If you have any questions, please contact client services at 412-209-7109 or 800-967-9672.
The following are reminders which should be reviewed prior to collecting specimens:
- 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)
- 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.
- Obtain venous blood by clean venipuncture. Avoid slow flowing draws and/or traumatic venipuncture as either of these may result in an activated or clotted sample. Do not use needles smaller than 23 gauge.
- Collection of blood through intravenous lines that have been previously flushed with heparin should be avoided if possible. If the blood must be drawn through an indwelling catheter, possible heparin contamination and specimen dilution should be considered. When obtaining specimens from indwelling lines that may contain heparin, the line should be flushed with 5 mL of saline and the first 5 mL of blood or 6-times the line volume (dead space volume of the catheter) should be drawn off and discarded before the coagulation tube is filled. If blood is obtained from a normal saline lock (a capped-off intravenous port), two dead space volumes of the catheter and extension set should be discarded.
- If only a blue top coagulation tube is to be drawn, a discard tube other than the blue tube may be drawn first to eliminate possible thromboplastin contamination from the site of the venipuncture.
- Use 3.2% (0.109 M) citrate (blue top) tubes for coagulation studies.
- Fill light blue top tubes as far as vacuum will allow. A ratio of 9 parts blood to 1 part anticoagulant must be maintained. Mix by gentle inversion. Underfilled tubes (less than 90% full) may affect testing accuracy because of over-citration. Overfilled tubes may not allow thorough mixing.
This next step is to be followed when specimens are drawn on the floor/outpatient facility and then must be transported to the specimen processing area either within your own facility or to your remote laboratory site:
- Following phlebotomy, samples should be transported at room temperature in a manner consistent with the institution's policy in order to avoid infectious potential. Transportation of whole blood specimens on ice is not acceptable for plasma-based coagulation assays because of possible cold activation of Factor VII, loss of von Willebrand factor, and platelet disruption. Extremes of temperature (high and low) during transportation must be avoided. Ideally, transport to the processing site or facility should occur within one hour of collection.
Upon receipt in the processing site at your facility:
- Immediately centrifuge the specimen as directed under individual assays. For coagulation testing, the following is recommended:
1500 x g15 minutes, preferably in a swinging bucket rotor
- Using a plastic pipet, remove the top 2/3 of plasma, transfer to labeled plastic tubes, and cap. Quick-freeze at -20°C or colder (preferrably -70°C or colder). Plasma should be frozen within 2 hours of drawing. NOTE: Plasma for Heparin Anti-Xa and ADAMTS-13 Activity levels should be frozen within 1 hour of collection.
- Specimens must remain frozen during storage and shipment to the Coagulation Laboratory. Ship on dry ice with guaranteed overnight delivery. Refer to shipping instructions below.
- 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 412-209-7109 for assistance.
|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|
Platelet Study Specimens
- Specimens for platelet testing must be received at testing facility within 3 hours of collection, and between the hours of 8:30am and 4:00pm, Monday through Friday.
- Specimens must be sent at room temperature as whole blood in 3.2% sodium citrate (blue top) tubes.
- Specimens that are received greater than 3 hours old may be rejected.
Platelet Associated Autoantibody Assay Testing
- Specimens must be drawn in EDTA (purple top) tubes for this procedure.
- Specimens must be received at testing facility within 24 hours of collection, and between the hours of 8:30am and 4:00pm, Monday through Friday.
- Specimens must be sent at room temperature as whole blood.
- All tubes for genetic testing must be sent at room temperature as whole blood. ACD (yellow top) tubes are preferred. EDTA (purple top) and sodium citrate (blue top) tubes are also acceptable.
- Specimens should ideally be received at testing facility within 3 days of collection, and no longer than 4 days of collection. A specimen may be rejected if it is received greater than 4 days after collection.
- Extracted nucleic acid sent for testing must include paperwork confirming that the DNA was extracted in a CAP certified lab.
- All specimens should have two (2) acceptable forms of patient identification.
- Acceptable forms of identification include the patient’s first and last name in addition to their medical record number or hospital identification number or birthdate. Do not use the patient’s Social Security Number.
- Coded specimens for research studies may use one form of identification if needed.
- Patient identification on the specimen must match the patient identification information on the requisition or the electronically transmitted data.
If a proper form of identification is not on the specimen(s) and requisition, the client service personnel will attempt to verify patient identification via a telephone call to your facility. If verification can be made, testing will proceed but a comment describing the lack of required identification will be included with the patient test reports or electronic files. If verification is difficult to obtain, testing will be delayed or will not proceed.
Specimen Rejection Criteria
Specimens may be rejected under the following general circumstances:
- Serum is unacceptable
- Lack of proper patient identification on specimen (2 forms of identification are required)
- Improper specimen(s) for test requested
- Inadequate volume of specimen for test requested
- Inappropriate anticoagulant for test requested
- Clotted whole (anticoagulated) blood or plasma
- Underfilled tubes (less than 90% full) for Coagulation testing
- Overfilled tubes that do not allow thorough mixing with anticoagulant
- Hemolyzed or grossly lipemic specimens
- Frozen whole blood specimens
- Leaking or broken specimen containers
- Improper storage of sample(s) before or during transport to laboratory
Please review the “Causes for Rejection” section for each test description test specific information.
The following checklist is helpful to ensure that the integrity of your specimen is maintained during collection and transport to the laboratory:
Are the following conditions consistent with the directions for each test?
- Temperature (ambient or frozen)
- Specimen type (whole blood, plasma, etc.)
- Specimen volume
- Patient/specimen properly identified
- Specimen container
- Lack of hemolysis
- All patient information is complete