25670:COAGULATION STUDY, PROLONGED ACTIVATED PARTIAL THROMBOPLASTIN TIME (APTT) EVALUATION
Alias Names:
Prolonged APTT Evaluation
Methodology:
Mechanical Clot Detection
Edit Date:
3/17/2009
Components:
Activated Partial Thromboplastin Time (APTT) / APTT Mixing Study / APTT Heparin Neutralized or Thrombin Time (TT) / Hexagonal Phospholipid Neutralization Test / Prothrombin Time (PT) / Russell Viper Venom Time (RVVT) / RVVT Lipid Neutralization. Not all these tests are performed on each specimen. Testing will vary depending on the nature and magnitude of the defect. Each panel includes a pathologist’s interpretation.
Performed:
Variable
Released:
In 7 days
CPT Code:
Varies
Specimen Collection Details
Collection:
Four 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 the maximum draw (at least 90% full). Mix by gentle inversion. Call the Special Coagulation Department (541.687.2134 x4612) when urgent testing is needed in order to assure STAT testing.
Handling:
Due to short stability, specimen must either be sent STAT to arrive at laboratory within 4 hours, or sent frozen. If STAT, refrigerate and keep capped in original tubes. Call for STAT pick-up. For standard delivery, centrifuge to produce platelet poor plasma (at least 1700 X G for 15 minutes) and using a plastic pipette, transfer the top 2/3 of the plasma into 3-4 plastic vials. Label with the patient name, I.D. number, test, and “citrated plasma.” Freeze immediately. Send to laboratory 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:
Four 4.5 mL light blue top tubes or 4 mL plasma.
Minimum Volume:
Two 2.7 mL light blue top tubes or 2 mL plasma.
Transport:
Original tubes refrigerated if STAT, or citrated plasma frozen on dry ice.
Comments:
Indicate if STAT testing is required. Indicate anticoagulant history and whether an abnormal coag diagnosis or family history exists. This panel is intended for the workup of unexplained prolonged APTT results. Patients on either coumadin or heparin will have a prolonged APTT and should not be evaluated until therapy has been discontinued. It is critical that patient plasma be ‘platelet-poor’ prior to freezing to prevent neutralization of lupus anticoagulants by platelet phospholipids. To check this, it is advisable to periodically perform a platelet count on plasmas which have been centrifuged for coagulation testing. The platelet count should be consistently below 10,000/cumm.
Rejection Criteria:
Visible fibrin; moderate to marked hemolysis; specimen received in laboratory beyond stated stability.
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