Anticoagulation Labs

Question 1

High citrate concentration in tube

Answer 1

Affects anti-factor Xa

Question 2

Poor blood samples

Answer 2

Increase both anti-factor Xa and aPTT

Question 3

Underfilled tubes

Answer 3

Increase aPTT

Question 4

Prolonged time > 2 hours to sample analysis

Answer 4

Decrease both anti-factor Xa and aPTT

Question 5

Inadequate centrifugation

Answer 5

Decrease both anti-factor Xa and aPTT

Question 6

Antithrombin deficiency

Answer 6

Decrease both anti-factor Xa and aPTT

Question 7

Increased acute phase reactants like factor 8 and fibrinogen

Answer 7

Decrease aPTT

Question 8

Increased heparin binding proteins

Answer 8

Decrease both anti-factor Xa and aPTT

Question 9

Obesity

Answer 9

Decreases both anti-factor Xa and aPTT

Question 10

Decreased renal elimination

Answer 10

Increase both anti-factor Xa and aPTT

Question 11

Decreased clotting factors (liver disease)

Answer 11

Increase aPTT

Question 12

Consumptive coagulopathy (DIC)

Answer 12

Increase aPTT

Question 13

Lupus anticoagulant

Answer 13

Increase aPTT

Question 14

Decreased clotting factors (Not factor 8)

Answer 14

Increase aPTT

Question 15

Elderly

Answer 15

Increase aPTT

Question 16

Recent use of other anti-Xa meds

Answer 16

Increase anti-factor Xa

Question 17

High triglycerides

Answer 17

Increase anti-factor Xa

Question 18

High bilirubin

Answer 18

Decrease anti-factor Xa

Question 19

COVID-19

Answer 19

Increase aPTT

Question 20

Should you wait for anti-Xa and aPTT baseline labs to result before starting a heparin infusion?

Answer 20

No, infusion should be started immediately and lab results can later influence dosing

Question 21

After a heparin infusion starts, when do you measure an anti-Xa level

Answer 21

4 - 6 hours after an infusion starts or infusion rate change without a bolus

Question 22

If a heparin bolus is given that is < 2500 units, when do you measure an anti-Xa level

Answer 22

6 hours after

Question 23

Since anti-Xa heparin assay is a chromogenic test, erroneous results can come from patients that have

Answer 23

Hemolysis, icterus, lipema (basically anything that affects how the blood looks)

Question 24

Anti-Xa heparin assay vs. Factor X assay

Answer 24

Anti-Xa heparin assay detects heparin’s effect of the patient’s plasma based on inhibition of factor X in an assay reagent; Factor X assay measures a patient’s endogenous level of functional Factor X

Question 25

What tests measure dabigatran?

Answer 25

Ecarin clotting assay, dilute thrombin time, or thrombin time

Question 26

What test measures enoxaparin?

Answer 26

Anti-Xa LMWH assay

Question 27

What is hematocrit?

Answer 27

Percent of red blood cells in the blood

Question 28

What is hemoglobin?

Answer 28

Presence of oxygenated blood

Question 29

What is d-dimer?

Answer 29

Product of fibrin degeneration

Question 30

What is a d-dimer determining?

Answer 30

If a d-dimer is negative, patient likely does not have a VTE. If a d-dimer is positive, do more tests.

Question 31

When to monitor platelets if heparin is started?

Answer 31

At baseline, 24 hours after, then every other day for 14 days

Question 32

When to draw a CBC for LMWH?

Answer 32

Every 5 - 10 days for the first two weeks, then every 2 - 4 weeks

Question 33

Critical prothrombin time value

Answer 33

> 100 seconds

Question 34

Critical aPTT value

Answer 34

> 70 seconds

Question 35

Critical chromogenic factor X level

Answer 35

11% or less

Question 36

Therapeutic anti-Xa heparin assay values

Answer 36

0.3 - 0.7 units/mL