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Old 04-08-2015
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Default Clotting deficiency question

FA 2015 P. 397 notes that Glanzmann's thrombasthenia is the result of a defect in GpIIb/IIIa.

Ristocetin, which used to diagnose some bleeding disorders, is noted to basically act as vWF in an unknown fashion. Normal bleeding time with ristocetin diagnoses vWF deficiency.

The notes then say that agglutination does occur with ristocetin assay.

How does this work if ristocetin only affects vWF, which is only involved in platelet adhesion, whereas GpIIb/IIIa is solely platelet aggregation?

Any ideas would be welcome
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Old 04-09-2015
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so this is what ive understood. Ristocetin is an antibiotic derivative which is now used to diagnose 2 conditions: VWD(where theres deficiency of this factor) and bernard soulier syndrome (where theres a defect in the receptor for vwf = gp1b)

now we must know that ristocetin basically cause vwf to bind to gp1b on the platelets and cause agglutination

if ristocetin is added to a blood which lacks the factor vwf or its receptor = agglutination will NOT occur (no clumping)

In FA i think its trying to say or rather differentiate between diagnoses of VWD and glanzmann, that in case of glanzman it has nothing to do with vwf so if u add ristocetin, clumping will occur

whereas in VWD , there is no factor, hence no clumping
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