Clinical Coagulation Laboratory

A division of Duke University Regional Referral Laboratory Services

Alert! Beware of falling CLOTS!

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Coagulation specimen processing/aliquoiting

Postive patient ID using barcode technology

LIS specimen barcode scanners

SPECIMEN COLLECTION AND PROCESSING INSTRUCTIONS

Reliable results in coagulation testing begin with proper sample collection. Specimens may be collected in evauated tube systems or by a two syringe technique. Collection tubes must be filled to complete vacuum volume and be inverted gently 6 times to mix. Specimens should be collected into siliconized glass or plastic.

The sample should be obtained without trauma. Care must be taken to avoid "artificially activating" the sample by placing the tourniquet on too tightly or for extended lengths of time. Air bubbles or foaming in the tubes or syringes should be avoided. Multiple sticks and patting the venipuncture site can also result in an unacceptable sample.

Correct identification of the patient and appropriate labeling of the specimen are paramount. The information should be provided on each specimen received by DUMC.

Note: Institutional barcodes/labels are acceptable if all of the above information is provided on the barcode/labels

Because of the nature of coagulation testing, specimens drawn locally must have the time of collection noted on the requisition. Specimens should be processed immediately and frozen plasma should be sent to DUMC within 4 hours of processing. If these guidelines are not followed, sample integrity may be affected and will be noted by DUMC on the final report form.

Citrated Plasma*

First draw a plain red top tube to remove tissue fluid contamination. Discard this tube. Then draw blood into a buffered citrate collection tube (light blue top) filled to the proper level. Soduim citrate of 0.109 or 0.129 M should be used. Use of other anticoagulants (unless otherwise specified) will cause invalid results. Invert gently 6 times to mix. Process immediately. Centrifuge the tube capped at 3500 rpm for 10 minutes to obtain platelet poor plasma. Remove plasma with plastic pipet into a plastic centrifuge tube and re-centrifuge for 10 additional minutes. Note: Samples for lupus anticoagulant testing must be platelet free (<10,000 platelets/mm3) prior to freezing. Dispense the plasma into plastic tubes using a plastic pipet. Label appropriately. Freeze Immediately. Send overnight on dry ice to DUMC Clinical Coagulation Laboratory. Samples must remain frozen at all times. See shipping instructions.

The ratio of whole blood to anticoagulant should be 9:1. If the patients's hematocrit is below 20% or above 55%, the amount of anticoagulant used should be adjusted according to the following formula:

• C=1.85 X 103 X (110H) X V where:
•  
• C=volume of 3.2% sodium citrate in milliliters
• H=hematocrit in percent
• V=volume of whole blood in milliliters

Note: Plasma specimens that have clotted or are collected with an improper anticoagulant cannot be evaluated for hemostatic disorders.

Serum

Draw plain red top tube. Allow to clot for 30 minutes. Centrifuge at 3000 rpm for 10 minutes. Dispense serum into plastic tubes. Label appropriately. Freeze immediately. Send overnight on dry ice to Duke University Clinical Coagulation Laboratory. Sample must be frozen at all times.

Anticoagulated Whole Blood (Sodium Citrate or EDTA)

Draw light blue top (3.2% sodium citrate) and/or a purple top (EDTA) tube. Gentely mix tube(s) six to 10 times by inversion. DO NOT Centrifuge. Label appropriately. Refrigerate or leave samples at room temperature. Do NOT Freeze. Send overnight at room temperature to Duke University Clinical Coagulation Laboratory.

Questions concerning collection techniques, methods, or supplies should be directed to the Clinical Coagulation Laboratory at DUMC by calling (800) 441-1416 or (919) 684-6366.

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Clinical Coagulation Laboratory
Duke University Medical Center
128 CARL Building
Box 3514
Research Drive
Durham, North Carolina 27710
(919) 684-6366
(919) 681-7673 FAX

Please send suggestions and comments to: wu000031@mc.duke.edu

Last Modified: September 13, 2003

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