27000:MIXING STUDY, ACTIVATED PARTIAL THROMBOPLASTIN TIME (APTT)
Alias Names:
Activated Partial Thromboplastin Time (APTT), Mixing Study / APTT MIXING STUDY
Methodology:
Mechanical Clot Detection
Edit Date:
9/19/2008
Performed:
Monday-Friday (STATS only on weekends)
Released:
24 hours
CPT Code:
85732 x3
Specimen Collection Details
Collection:
Three 4.5 mL light blue top tubes (sodium citrate). Collect by careful venipuncture to avoid tissue fluid contamination or hemolysis. Do not use needles smaller than 23 gauge. Fill tubes to maximum draw (at least 90% full). Mix by gentle inversion.
Handling:
Due to short stability, specimen must either be sent STAT to arrive in testing department within 4 hours or sent frozen. For STAT, refrigerate and keep capped in original tube. Call for STAT pick-up. For standard delivery, centrifuge plasma (at least 1700 X G for 15 minutes) and using a plastic pipette, transfer the top 2/3 of the plasma into a plastic vial. Label with patient name, I.D. number, test, and “citrated plasma.” Freeze immediately. Send to PeaceHealth Laboratories within 7 days. If multiple tests are ordered, freeze a separate aliquot for this test.
Stability:
4 hours ambient or refrigerated, or 7 days frozen.
Standard Volume:
Three 4.5 mL tubes whole blood or 4 mL plasma.
Minimum Volume:
Two 1.8 mL whole blood or 2 mL plasma.
Transport:
Original tubes refrigerated if STAT, or citrated plasma frozen on dry ice.
Comments:
Indicate if patient is on coumadin or heparin therapy. Note that heparin is a coagulation inhibitor and will produce an abnormal mixing study result. To more specifically demonstrate the presence of heparin, Activated Partial Thromboplastin Time (APTT), Heparin Neutralized (25150) is recommended. Correction of the APTT following heparin neutralization indicates the presence of heparin. When drawing from heparin lines, withdraw slowly and discard at least 10 mL of blood to clear before drawing specimen. For optimal detection of lupus inhibitors, platelet-poor plasma must be prepared to prevent neutralization of the antibody by platelet phospholipids. It is advisable to periodically check the platelet count of ”platelet-poor plasma” to assure that it is consistently below 15,000/cumm. If not, centrifuge spin time and/or speed should be increased. See also Coagulation Study, Anti-Phospholipid Panel (25620).
Rejection Criteria:
Visible fibrin; moderate to marked hemolysis; normal APTT; non-frozen specimen received in testing department more than 4 hours after collection.
Reference Range:
Normal = Negative for coagulation inhibitor. Pathologist interpretation accompanies report.
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