Anticoagulants and Tests Flashcards
Heparin
Unfractionated: not functional in patients with antithrombin deficiency, monitored with PTT
LMWH: only inhibits factor Xa, no effect on thrombin, monitor with anti-Xa assay
Warfarin
Dicoumarol, coumadin Inhibits vitamin K synthesis Therapeutic range is INR of 2-3 Factor VII is the first factor to decrease Monitored with PT
Direct Oral Anticoagulants (DOACs)
Do not require regular blood tests
Xa inhibitor: apixaban, edoxaban, rivaroxabab
IIa inhibitor: dabigatran
Prothrombin Time
Use light blue/sodium citrate tube filled to the line
1:9 ratio of anticoag to blood
Measures the extrinsic pathway
11.9 to 15.1 seconds
INR
Uses ISI for uniformity
Calculated from PT, lower ISI is more responsive
0.8 to 1.2
Partial Thromboplastin Time
Used to monitor heparin therapy
Measures the intrinsic pathway
25 to 35 seconds
Anti-Xa Test
Monitors LMWH therapy
Follow Up Testing
PT/PTT prolonged: consider coag factor deficiency or circulating anticoag
PLT count low/high: consider thrombocytopenia, aplastic anemia, thrombocythemia, acute leukemia, DIC
All tests normal: consider PLT function test or vascular disorders
Platelet Aggregation Testing
Measures light impedance of platelet rich plasma
Graphs have the Y axis from high optical density to ow going up on the axis
Mixing Studies
1:1 ratio of normal plasma to patient plasma
Cause is factor deficiency, PT/PTT corrected
Cause is circulating anticoag, PT/PTT not corrected
Thrombin Time
Add thrombin and measure time
15 to 19 seconds
Reptilase test: distinguishes between heparin (normal) fibrin degradation products (abnormal)
18 to 22 seconds
RVVT
Venom activates V and X
VII deficiency will give a prolonged PT, normal RVVT
X deficiency will give a prolonged PT and RVVT
dRVVT used for detecting lupus anticoag
D-Dimer
Tests for the presence of clots
Anti-Xa
Monitors LMWH therapy
