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Test Code APTT Activated Partial Thromboplastin Time (aPTT), Plasma

Important Note

Due to specimen stability issues, this test cannot be collected at sites other than St Joseph Hospital.  Please ask patients to come to the hospital lab for their specimen collection.

Additional Codes

EPIC:  LAB325

Methodology

Chromogenic

Performing Laboratory

St. Joseph Hospital

Specimen Requirements

Collect a full, light blue-top (3.2% sodium citrate) tube. (Hemolyzed specimen is not acceptable.) Centrifuge at 2,500 rpm for 15 minutes or 3,000 rpm for 10 minutes. 

Note:  centrifuged specimen is stable for 4 hours at ambient temperature.

Reference Values

24.1 - 35.1 seconds (without anticoagulant therapy)

71-98 seconds (therapeutic)

Critical values:  <20 or >100 seconds

Note:  Values may vary with reagent lot changes. Always refer to patient chart for current range.

Day(s) Test Set Up

Monday through Sunday

Available STAT

Test Classification and CPT Coding

85730

Clinical Significance

The activated partial thromboplastin time (aPTT) is a general coagulation screening test of the coagulation factors XII, XI, IX, VIII, X, V, II and fibrinogen.   Abnormal aPTT results are encountered in congenital and acquired clotting factor deficiencies, liver diseases, circulating anticoagulants (LA type or circulating anticoagulant against a factor) and during heparin or oral anticoagulant therapy.