From the Guidelines
Ristocetin-induced platelet aggregation (RIPA) testing is crucial for distinguishing between subtypes of von Willebrand Disease (vWD), with each subtype exhibiting unique patterns of platelet aggregation in response to ristocetin. The results of RIPA testing can help identify the specific subtype of vWD, which is essential for determining the appropriate treatment and management plan.
Subtypes of vWD and RIPA Results
- Type 1 vWD: reduced aggregation at normal ristocetin concentrations (1.0-1.5 mg/mL) but normal aggregation at higher concentrations, reflecting the quantitative deficiency of von Willebrand Factor (vWF) 1.
- Type 2A vWD: markedly decreased aggregation at all ristocetin concentrations due to the absence of high molecular weight vWF multimers 1.
- Type 2B vWD: paradoxical enhanced response at low ristocetin concentrations (0.5-0.7 mg/mL) where normal platelets wouldn't aggregate, indicating increased affinity of vWF for platelet glycoprotein Ib 1.
- Type 2M vWD: decreased aggregation similar to Type 2A, but with normal multimer distribution 1.
- Type 2N vWD: normal RIPA results since the defect affects Factor VIII binding rather than platelet interaction 1.
- Type 3 vWD: absent or severely reduced aggregation at all ristocetin concentrations due to the virtual absence of vWF 1.
Importance of RIPA Testing
RIPA testing is valuable because it functionally assesses vWF-platelet interaction, providing insights beyond quantitative measurements and helping distinguish between vWD subtypes, particularly Type 2B from other variants 1. The results of RIPA testing should be interpreted in conjunction with clinical evaluation and other laboratory tests, such as VWF antigen and VWF ristocetin cofactor activity, to establish a definitive diagnosis and determine the severity of vWD 1.
From the Research
Ristocetin-Induced Platelet Aggregation (RIPA) Results for Von Willebrand Disease (VWD) Subtypes
- Type 1 VWD: RIPA is typically normal 2, 3
- Type 2A VWD: RIPA is normal 3
- Type 2B VWD: RIPA is increased 4, 5, 3
- Type 2M VWD: RIPA is decreased 3
- Type 3 VWD: RIPA is decreased 6
- CvWD Vicenza: The vWF:RCof/Ag ratios are completely normal before and after DDAVP, and RIPA results are not specifically mentioned 3
- CvWD types 2C, 2D, and 2E: RIPA results are not specifically mentioned, but these types are featured by very low functional vWF parameters and abnormal vWF multimers 3
- CvWD type 2N: RIPA results are not specifically mentioned, but this type usually presents with much lower levels for FVIIIc as compared with vWF, normal Ivy BT, and normal vWF multimeric pattern 3
Factors Affecting RIPA Results
- Aspirin ingestion: Inhibits the second phase of RIPA at low concentrations of ristocetin only 2
- Desmopressin therapy: Increases VWF binding to platelets, which can be measured by flow cytometry-based assays 4
- Plasma von Willebrand factor (VWF) multimers: Absence of high VWF multimers can lead to abnormal RIPA results 5, 3