OHSU

Hemostasis and Thrombosis

Hemostasis and Thrombosis offers diagnostic testing for bleeding and thrombotic conditions.  It is not responsible for routine coagulation procedures such as PT, APTT, Fibrinogen, or D-Dimer, but performs the more esoteric assays in the diagnosis of acquired or congenital protein defects. Includes APC resistance, coagulation factors, heparin therapy monitoring, Protein C, anticardiolipin antibodies, Lupus inhibitors, etc.

The lab is staffed Monday through Friday, 8:00am to 4:30pm, and can be reached directly at 503 494-8445. Urgent work outside these times must be cleared by the Laboratory Medicine Resident on call at 503 494-4799, #7005.

Specimen collection, processing, storage, and shipping are critical to obtain valid results for hemostasis tests. Please follow these instructions for all tests requiring frozen citrated plasma for the Hemostasis & Thrombosis Lab. Please call 503 494-8445 if questions.

Drawing Samples

Draw blood into siliconized evacuated tubes or plastic syringes containing buffered sodium citrate anticoagulant (light blue top tubes). The tubes must be filled to the fill line on the tubes.

Do not use the first tube/syringe for hemostasis samples. The first tube may contain tissue factor, which will cause activation of coagulation. The venipuncture must not be traumatic or slow flowing; avoid leaving the tourniquet on for an extended time. hemolyzed or clotted specimens are unacceptable.

Evacuated tubes must fill by vacuum completely. Immediately after filling, mix tubes gently by inversion. Samples must be kept capped and  processed immediately. If necessary, sample may be stored on wet ice or at 4°C for up to 2 hours before processing.

Processing

Centrifuge at a minimum of 2000 x g for 20 minutes, in a refrigerated centrifuge, if available. Alternative protocols are acceptable if the plasma platelet count is less than 10,000/mm3. If necessary, transfer plasma to a plastic tube and re-centrifuge to remove platelets. This is critical for the detection of lupus anticoagulants. Do not filter the plasma to remove platelets, as filtering will remove high molecular weight von Willebrand Factor.

Using a plastic pipette, remove the top 2/3 of plasma and transfer to labeled plastic tubes and cap. Glass tubes are unacceptable because glass activates the hemostatic mechanism. Samples must be frozen within 2 hours after drawing. (Quick freeze at -60°C or colder. Samples stored at -80°C are stable for 1 year; samples stored at -20°C are stable for only 2 weeks.)

Samples must remain frozen during storage and shipment. Ship on dry ice with guaranteed overnight delivery.

Published Reference Ranges for Coagulation Tests for Children Less than 6 Months Old