Special Instructions Collection date and time must be on the requisition. A special tube must be obtained from the laboratory if the hematocrit is >55% or <20%
Collection Routine venipuncture. If multiple tests are being drawn, draw coagulation studies last. If only a partial thromboplastin time (PTT) is being drawn, draw 1-2 mL into another Vacutainer®, discard, and then collect the PTT. This collection procedure avoids contamination of the specimen with tissue thromboplastins. If drawing from arterial line or any line flushed with heparin, discard the first 20 mL of blood to prevent contaminating specimen.
Storage Instructions Separate plasma and refrigerate if specimen cannot be processed immediately.
Patient Preparation Draw specimen 1 hour before next dose of heparin if heparin is being given by intermittent injection; not applicable to patients on continuous heparin infusion therapy. Do not draw from an arm with a heparin lock or heparinized catheter.
Causes for Rejection Specimen clotted, hemolyzed, contaminated with heparin (ie, drawn with blood gases), received more than 2 hours after collection; tubes not full, specimen container not labeled according to labeling criteria
Reference Range 24.2-35.2; therapeutic range for heparin is 64-112 seconds.
Use Evaluate intrinsic coagulation system, monitor heparin therapy; screen for presence of classical hemophilia A and B; congenital deficiencies of factors II, V, VIII, IX, X, XI, and XII; dysfibrinogenemia; disseminated intravascular coagulation; liver failure; congenital hypofibrinogenemia; vitamin K deficiency; congenital deficiency of Fitzgerald factor; congenital deficiency of prekallikrein (Fletcher factor)
