Why does prothrombin G20210A increase the risk of thrombosis? ...

[FButt]

Why does prothrombin G20210A increase the risk of thrombosis?
 
  a. Makes prothrombin activation easier
  b. Elevates prothrombin levels
  c. Decreases binding of thrombin by antithrombin
  d. Decreases binding of plasminogen to prothrombin

Question 2

When the chromogenic assay for antithrombin is performed, which of the following is true?
 
  a. The colored end-product intensity is inversely proportional to the antithrombin concentration.
  b. The chromogenic substrate is bound by antithrombin.
  c. Warfarin is added to the patient sample before testing to improve sensitivity.
  d. Activated protein C competes for the chromogenic substrate, so it must first be selectively removed.

[k.lashomb]

Answer to Question 1

ANS: B
The prothrombin G20210A mutation results in elevated levels of prothrombin; this increases the risk of thrombosis, although the reason why is not clear.

Answer to Question 2

ANS: A
Antithrombin concentration is inversely proportional to the intensity of end-product color. Heparin is added to the patient plasma before testing to improve sensitivity to antithrombin. A protease, often Xa, is added in excess to an aliquot of the patient sample. Some of this Xa will be bound by the heparin-antithrombin complex and thus inhibited. After this, a chromogenic substrate is added that is specific for Xa. When the residual Xa hydrolyzes this substrate, color will be released. The more antithrombin present in the patient sample, the more Xa will be bound and the less chromogen will be released.

[FButt]

TYSM

[peter]

Excellent