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Test Code LAB335 Ristocetin Cofactor, Blood or Plasma

Additional Codes

46860

Reporting Title

Ristocetin Co-factor Assay

Methodology

Platelet Aggregation with Ristocetin

Used to detect abnormalities of von Willebrand factor which is associated with von Willebrand’s syndrome.

Performing Laboratory

OhioHealth Laboratory Services-RMH Core Coagulation

Specimen Requirements

Submit only 1 of the following specimens:

 

Riverside Inpatient and Riverside Campus draw sites:

Testing must be performed within 4 hours of draw if submitting unprocessed whole blood.

Draw a full, light blue-top (citrate) tube; and send citrated whole blood. Invert several times to mix blood. Forward unprocessed whole blood promptly at ambient temperature only. Do not refrigerate.

Note:  1. This assay requires its own specimen.

2. Indicate whole blood on request form.

3. Label specimen appropriately (whole blood).

 

Outpatient/Outreach Clients:

Plasma-Frozen

Draw a full, light blue-top (citrate) tube. Spin down, remove plasma, spin plasma again, and place 1 mL of citrated platelet-poor plasma 2 in plastic vials. (Glass vial is not acceptable.) Pour-off vial should be no more than 2/3 full. Send specimen frozen.

Note:  1. This assay requires its own specimen.

2. Double-centrifuged specimen is critical for accurate results as platelet contamination may cause spurious results.

3. Indicate plasma on request form.

4. Label specimen appropriately (plasma).

Specimen Transport Temperature

Ambient/Refrigerate NO/Frozen NO-Blood

Frozen/Refrigerate NO/Ambient NO-Plasma

Reference Values

Adults:  50-150%

Results of <40% von Willebrand factor are considered abnormal and suggest von Willebrand’s disease. Values >40% do not rule out the possibility of a variant of von Willebrand’s. Diagnosis of variant forms necessitates a series of clinical and laboratory evaluations including patient and family histories, platelet function assay, factor VIII related antigen, and factor VIII activity level.

Day(s) Test Set Up

Monday through Friday

Test Classification and CPT Coding

85245