Explain the effects of the following on coagulation testing:

a. Clotted sample
b. Ratio of blood to anticoagulant < 9:1
c. Patient hematocrit >55%
d. >1-hour difference between specimen collection and analysis

What will be an ideal response?

Answer:
Clotted sample: Because factors are consumed in the formation of the clot in the tube, they will be unavailable to form a clot in vitro. The result will be a prolonged time with the coagulation tests.
Ratio of blood to anticoagulant <9:1: There will be too much anticoagulant for the amount of plasma present. This will cause the specimen to be over-anticoagulated and thus cause a prolongation in the clot-based assay times.
Patient hematocrit >55%: The proportion of cells to plasma will not be optimal for the amount of anticoagulant present in the tube, resulting in the same scenario as in b.
>1-hour difference between specimen collection and analysis: Depending on the length of time elapsed between specimen collection and analysis, a delay in processing and testing the sample can cause the labile factors in the sample to degrade and prolong clotting times.