Hematology

Question 1

Which type(s) of VWD show RIPA at low dose ristocetin?

Answer 1

Type 2B and platelet-type VWD (increased affinity to GP1b binding)

Question 2

How can you differentiate between Type 2B and platelet-type VWD?

Answer 2

VWF:platelet binding assay, uses platelets from normal individual. Type 2B will still show RIPA to low dose ristocetin, but platelet-type will not.

Question 3

What factors affect VWF:Ag levels?

Answer 3

ABO type (much lower in type O), pregnancy, menstrual cycle, hormonal contraceptives, hypothyroidism, systemic inflammation, exercise, surgery, anxiety

Question 4

What treatment(s) can be used for patients with antibodies to VWF?

Answer 4

Factor VIII concentrates. Acquired VWD with autoantibodies, or alloantibodies seen in Type 3 VWD exposed to plasma products.

Question 5

What are the potential mechanisms for acquired VWD?

Answer 5

Hypothyroidism, drugs (VPA, cipro, griseo, HES). Autoimmune clearance (AI ds, LPD, cancer). Shear-induced from CV lesions, ECMO. Incr binding of VWF to plts or other cells (MPD).

Question 6

In VWD, where will you see decreased Factor VIII levels?

Answer 6

In type 3 VWD, which will be alongside very low VWF:Ag and VWF:RCo. In type 2B VWD, but usually with normal VWF:Ag and VWF:RCo and can be diagnosed with VWF:F8 binding assay.

Question 7

What will multimeric analysis show in different types of VWD?

Answer 7

Absence of HMW multimers in type 2 A (defect in site of multimerizing or incr degradation), type 2B and platelet-type (incr degrad of large plt-VWF aggregates). No multimers seen in type 3.

Question 8

In what type(s) of VWD will you see thrombocytopenia

Answer 8

Type 2B and platelet-type VWD. Some forms of acquired VWD (e.g. in MPD).

Question 9

What is the goal for VWF:F8 concentrate dosing?

Answer 9

Aim for a peak (30-90 mins after admin) of 100 IU/dl of VWF:RCo and a trough above 50 IU/dL. Try not to exceed VWF:RCo of 200 IU/dL or F8 of 250-300 IU/dL.

Question 10

What is the half life of two primary VWF:F8 concentrates? Standard dosing?

Answer 10

Humate-P (2.4:1 VWF:RCO to F8) with 6-8 hr half-life vs. Alphanate (1.3:1 R:Co to F8) with 10-12 hr half-life
Usually dosed in VWF:RCo units. Major bleeding/surgery loading dose 40-60 IU/kg w/ maintenance of 20-40 IU/kg q8-24 h. Minor bleeding/surgery loading dose 30-60 IU/kg w/ maintenance dosing of 20-40 IU/kg q12-48h.