Thrombophia

Question 1

Principle of RVV

Answer 1

Russell’s viper venom (RVV) activates factor X, leading to a fibrin clot in the presence of factor V, prothrombin, phospholipid and calcium ions. A LAC prolongs the clotting time by binding to the phospholipid and preventing the action of RVV. dilution of the venom and phospholipid makes it particularly sensitive for detecting a LAC.7 Because RVV activates factor X directly, defects of the contact system and factor VIII, IX and XI deficiencies do not influence the test. The DRVVT should be combined with a platelet/phospholipid neutralization procedure to add specificity and this is incorporated into several commercial kits.

Question 2

Low protein c

Answer 2

oral anticoagulant therapy. 
 DIC, 
sepsis (especially meningococcal septicaemia), liver disease
sickle cell disease 
 early postoperative period.

Question 3

What is lupus anticoagulant

Answer 3

LACs are immunoglobulins that bind to certain proteins when bound to phospholipid. The effective sequestration of phospholipid can then cause prolongation of phospholipid-dependent coagulation tests such as the prothrombin time (PT) or activated partial thromboplastin time (APTT).

Question 4

Method of dilute rvv test

Answer 4

Place 0.1 ml of pooled normal plasma and 0.1 ml of dilute phospholipid reagent in a glass tube at 37°C. Add 0.1 ml of dilute RVV and, after warming for 30 s, add 0.1 ml of CaCl2. Record the clotting time. Repeat the sequence using the test plasma. Calculate the ratio of the clotting times of the test and control (normal pool) plasma.

Question 5

What is dilute RVV ratio

Answer 5

ratio of the clotting times of the test and control (normal pool) plasma usually up to 1.02 s
Greater than this suggests lac

Question 6

DDx for driving ratio > 1.05s

Answer 6

ABN F2, 5, 10 f’gen or inhibitor

Question 7

How to differentiate if LAC vs inhibitor

Answer 7

mixing test first to confirm the presence of an inhibitor and to exclude a factor deficiency then to confirm Apab
LAC- plt neutralisation procedure

Question 8

Criteria for catastrophic apls

Answer 8

Evidence of involvement of 3 or more organs
Development over a week
Confirmation of histopatholohy if small vessel occlusion
Lab confirmation of apls

Definite if all 4 present
Probable if 1,2 and 4. 1,3,4 with a third event

Question 9

Other things occuring with catastrophic apls

Answer 9

Thrombocytopenia

Haemolytic anaemia

Question 10

Method or protein c testing

Answer 10

Elisa- sandwich method, cheap, rapid,
EIA- laurell rocker
Commercial, expensive, small batch size

Question 11

Ddx arterial and venous clot

Answer 11

§Defects in clot lysis (Dysfibrinogenemia*, Deficiency of plasminogen-activator inhibitor type 1)

§Metabolic (Homocysteinemia)

§Platelet disorders (HIT,Myeloproliferative disorders, PNH, Polycythemia vera (with thrombocytosis))

§Hyperviscosity(Polycythemia vera, Waldenström’s macroglobulinemia, Sickle cell anemia, Acute leukemia)