The activated partial thromboplastin time (aPTT) test is a screening procedure used primarily to determine deficiencies in factors necessary for the formation of intrinsic prothrombin activator, namely factors VIII, IX, XI and XII.

Factors II, V and X deficiencies (normally detected by the prothrombin time) can also be detected by the aPTT.

The test will not detect platelet disorders, isolated factor XII and factor XIII deficiencies.

Lt blue Sodium citrate (NaCit) - 2.7mL

If the patient has a hematocrit >55, a specially prepared Lt blue Sodium citrate (NaCit) tube must be used in place of the standard Lt blue Sodium citrate (NaCit) tube.

Hematocrit-Anticoagulant adjustments

• Do not over or under fill tube as the ratio of anticoagulant to whole blood is critical

Coag – tube fill guidelines

• Immediatley following collection, mix sample by gentle inversion 3 - 4 times to prevent clotting

• Process Platelet Poor Plasma (P.P.P)

  • Coag – how to prepare a specimen for special coagulation testing

• Transfer plasma into an aliquot tube using a spot label "NaCit Plasma P.P.P" to label as platelet poor plasma
• Freeze immediately

Microcentrifuge vial/tube in a Snap cap conical vial/tube and cap (Beaker sites)

Coagulation specimen transport vial/tube  (all other sites)

Lt blue Sodium citrate (NaCit) - 2.7mL

Routine:

Frozen (strict)

Refrigerated - NO

STAT:

Ambient

• Patient not on heparin: 4 hours
• Patient on heparin: specimen must be processed within 1 hour of collection, and testing run within 2 hours of collection.

• Improper label (unlabeled or mislabeled)
• Improper anticoagulant
• Improperly filled tube
• Hemolysis
• Clotted specimen
• Delay in transport
• Improper storage/transport temperature
• Patient on heparin > 1.0 IU/mL

Clot Based Assay

0-2 months:  29 - 50 seconds

3-6 months:  28 - 43 seconds

Adult:           25 - 36 seconds

Heparin therapeutic range: 59 - 89 seconds

0 - 28 days of age or outpatient: > 60 seconds

Medical necessity