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Test Code 76213672 Ristocetin Cofactor Activity, Plasma

Performing Laboratory

Barnes-Jewish Hospital Laboratory



Literature References:

Ristocetin CoFactor Assay, Chrono-log Corporation, 2 West Park Road, Havertown, PA 19083-4691, Rev. 07/2014

Specimen Requirements

This test is lab orderable only as a von Willebrand Factor Activity reflex.

It may be performed by special arrangement only. Physician must contact Laboratory Medicine resident at digital pager 314-747-1320 for approval before ordering.

Specimen Type: Plasma

Container/Tube: Light-blue top (citrate)

Specimen Volume: 1 Full tube

Specimen Minimum Volume: Full tube

Collection Instructions:

1. Draw a discard tube prior to light-blue top (citrate) tube.

2. Tube should remain stoppered.

3. Do not centrifuge.

4. Clotted blood or an insufficient specimen is not acceptable.

5. Avoid hemolysis and heparin contamination of specimen.

Analyte Stability:

4 hours at 18° C to 24° C if the top has not been removed.
2 hours at 18° C to 24° C after the top has been removed.
Platelet-free plasma can be stored  6 months at -70° C.
Additional Information: If the patient is a hospital patient and the hematocrit is >55%, call Barnes-Jewish Hematology Laboratory at 314-362-5203 for instructions.

Day(s) Test Set Up

Monday, Thursday

Cut-off time: 0700

Turnaround Time:

STAT: not available

Routine: results available the day of testing



Reference Values


Literature References:

1. Triplett DA. Laboratory diagnosis of von Willebrand’s disease. Mayo Clin Proc 1991;66:832-840.

2. Sadler JE. A revised classification of von Willebrand disease. Thrombosis and haemostatis. FK Schattauer Verlagsgesellschaft mbH (Stuttgart), 1994;71;520-5.

Test Classification and CPT Coding


Additional Information

For BJH Laboratory Use Only

Analyte Stability:

4 hours at 18° C to 24° C if the top has not been removed.
2 hours at 18° C to 24° C after the top has been removed.
Platelet-free plasma can be stored 6 months at -70° C.

Laboratory Processing Instructions:

Test performed in BJH Hematology.

Specimen Transport Temperature

Ambient/Refrigerate NO/Frozen Yes

Ambient Whole Blood:  4 hours at 18° C to 24° C

Frozen Platelet-Free Plasma: 6 months at -70° C