Ristocetin Cofactor Test
Short Name: vWF:RCo
Also known as: vWF:RCo, Ristocetin Cofactor Activity, Von Willebrand Factor Ristocetin Cofactor, Ristocetin Aggregation Test
Ristocetin Cofactor Test test available at DNA Labs India for ₹20,000. Uses Platelet Agglutination on Whole blood (Plasma) samples. Results in Samples are accepted by the 7th of the month for batch testing. Reports are typically issued within 2-3 weeks from the sample receipt date.. Free home collection in 300+ cities across India.
🩺 Medically Reviewed By
Dr SULOCHANA HEMCHANDRA HOLLA
Consultant Medical Geneticist · Reg: 8532
Last reviewed: September 7, 2026
Overview
The purpose of the Ristocetin Cofactor Test is to measure the functional capacity of von Willebrand factor in promoting platelet adhesion. It is used to diagnose von Willebrand disease, to differentiate its types, and to assess the response to treatment.
- Test Code
- 3607
- CPT Code
- 85245
- ICD Code
- D68.0
- Price
- ₹20,000
- Sample Type
- Whole blood (Plasma)
- Result Time
- Samples are accepted by the 7th of the month for batch testing. Reports are typically issued within 2-3 weeks from the sample receipt date.
- Fasting Required
- Yes (10 hours)
- Method
- Platelet Agglutination
Sample Collection
Overnight fasting is mandatory before the blood sample is taken. Please drink plain water if needed. Inform your doctor about any medications, especially blood thinners or factor replacement therapy, as they may affect the test results. Duly filled Coagulation Requisition Form (Form 15) and Test Send Out Consent Form (Form 35) are required.
Method: Venipuncture
Laboratory Analysis
A trained phlebotomist will collect approximately 3 mL of venous blood into a blue-top (sodium citrate) tube. The tube must be mixed thoroughly by gentle inversion to prevent clotting. Avoid shaking the tube vigorously.
Report Delivery
The sample must be transported to the laboratory within 4 hours. If transport cannot be done within this time, the sample should be processed to make platelet-poor plasma (PPP) within 1 hour of collection. The PPP must be frozen immediately and shipped on dry ice. Do not thaw the sample before testing.
Timeline: Samples are accepted by the 7th of the month for batch testing. Reports are typically issued within 2-3 weeks from the sample receipt date.
Patient Instructions
About This Test
Who Should Get This Test
The purpose of the Ristocetin Cofactor Test is to measure the functional capacity of von Willebrand factor in promoting platelet adhesion. It is used to diagnose von Willebrand disease, to differentiate its types, and to assess the response to treatment.
How to Prepare
- Use a 3 mL blue-top sodium citrate tube (3.2% or 3.8%)
- Perform venipuncture smoothly to avoid platelet activation
- Fill the tube completely to maintain the correct blood-to-anticoagulant ratio
- Mix the tube by gently inverting 4-6 times immediately after collection
- Transport the whole blood sample to the laboratory within 4 hours at room temperature
- If delayed, centrifuge the sample at 3600 rpm for 15 minutes, transfer plasma to a clean plastic tube, centrifuge again, and freeze the final platelet-poor plasma at -20°C or lower
- Ensure the sample is labelled with patient identification and collection time
Doctor's Notes
Reviewed by Dr SULOCHANA HEMCHANDRA HOLLA — MBBS, MD (Medical Genetics) · Reg. No. 8532
"The ristocetin cofactor assay is a cornerstone in the diagnosis of von Willebrand disease. Accurate results depend on careful patient preparation and immediate sample processing. I always advise my patients to follow the fasting and sample transport instructions to avoid the need for repeat testing."
Last medically reviewed: September 7, 2026
Test Parameters & Specifications
Sample Stability
- Clotted sample
- Hemolyzed or lipemic sample
- Underfilled or overfilled tube
- Sample not transported or processed within the required time
- Improperly labelled sample
- Sample received without completed requisition and consent forms
Understanding Your Results
Low vWF:RCo with low vWF antigen
Suggests type 1 vWD (quantitative deficiency)
Low vWF:RCo with normal vWF antigen
Suggests type 2 vWD (qualitative defect, e.g., type 2A, 2B, 2M)
Normal vWF:RCo with borderline vWF antigen
May require repeat testing or further investigation for mild vWD
Low vWF:RCo with very low factor VIII
Could indicate type 3 vWD or a combined factor deficiency
If you have a history of unexplained bruising, prolonged bleeding, or a family member with vWD, consult your doctor about screening tests. Immediate medical attention is needed for bleeding that does not stop with pressure, severe heavy menstrual bleeding, or bleeding into joints or muscles.
Limitations
- ⚠The vWF:RCo assay has high assay variability, especially at low levels (<20%)
- ⚠It cannot detect all functional variants of vWD; other tests such as vWF antigen and factor VIII levels are needed
- ⚠Ristocetin cofactor activity may be affected by platelet count and quality of the platelet reagent
- ⚠Results should be interpreted in the context of the patient's clinical picture and bleeding score
Risks & Considerations
- ●Minor pain or discomfort at the puncture site
- ●Bruising or swelling after blood draw
- ●Dizziness or lightheadedness
- ●In rare cases, infection or excessive bleeding
Interfering Factors
- ●Improper sample collection (e.g., overfilled or underfilled citrate tube) leading to incorrect anticoagulant-to-blood ratio
- ●Hemolysis or lipemia in the sample
- ●Delayed processing or storage at incorrect temperature
- ●Elevated haematocrit (>55%) causing relative citrate excess
- ●Recent infusion of desmopressin or vWF/factor VIII concentrates
- ●Presence of lupus anticoagulant or other platelet-interfering antibodies
Compare With Similar Tests
| Test | Ristocetin Cofactor Test | Von Willebrand Factor Antigen | Von Willebrand Factor Activity (vWF:Ac) | Factor VIII Assay |
|---|---|---|---|---|
| Comparison | Ristocetin Cofactor Test |
Frequently Asked Questions
What is the Ristocetin Cofactor Test?
Why is the test called 'Ristocetin Cofactor'?
What does the Ristocetin Cofactor Test diagnose?
Do I need to fast for the Ristocetin Cofactor Test?
What sample is needed for the Ristocetin Cofactor Test?
How is the Ristocetin Cofactor Test performed?
What is the normal value of Ristocetin Cofactor?
What does a low Ristocetin Cofactor level mean?
Can medications affect the Ristocetin Cofactor Test?
What is the cost of the Ristocetin Cofactor Test in India?
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Is home sample collection available for this test?
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