Sources of Error in Coagulation Testing Hematology Review 364
ERROR COMMENT
Incorrect anticoagulant
Drawing coagulation tube
after other anticoagulant tubes
Probing to find vein
Incorrect ratio of blood to
anticoagulant
Failure to mix anticoagulant with blood
Polycythemia
Heparin contamination from
catheter or heparin lock
Hemolysis
Lipemia
3.2% sodium citrate should be used. Labile factors are preserved better.
Contamination with other anticoagulants can interfere.
Tissue thromboplastin activates coagulation & ↓times.
Need 9:1 blood to anticoagulant ratio. Tubes <90% full will have longer times.
Blood will clot.
HCT >55% leads to longer times. Anticoagulant must be reduced.
Will prolong times. Lines must be flushed with saline, first 5 mL drawn discarded.
Hemolyzed RBCs may activate clotting factors. Hemolysis may interfere with photometric
reading.
May interfere with optical methods. Test by mechanical method.
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