Test Catalog

Test ID: APRI    
Prolonged Clot Time Profile Interpretation

Useful For Suggests clinical disorders or settings where the test may be helpful

Determining the cause of prolongation of prothrombin time or activated partial thromboplastin time


Screening for prolonged clotting times and determining the presence of factor deficiencies or inhibitor (eg, factor-specific, lupus-like, or the presence of heparin)

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

When coagulation screening tests are performed to verify normal function of the coagulation system (eg, preoperative, routine examination), they sometimes indicate an abnormality that may be unexplained (ie, prolonged clotting times). This consultation provides as comprehensive a workup as needed to define the abnormality and validation of the prolongation. .


Possibilities for a cause of prolongation include:

-Artifactual due to high hematocrit (-dilution of specimen by anticoagulant if patient hematocrit is 55% or greater)

-Factor deficiencies, congenital or acquired

-Factor inhibitors eg, factor VIII inhibitors (bleeding disorder)

-Lupus anticoagulant (risk for thrombosis or recurrent miscarriage)

-Anticoagulant drug effect including warfarin: Coumadin or Jantoven, oral anti-Xa inhibitors, oral direct thrombin inhibitors, and heparin.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

Only orderable as part of a profile. For more information see APROL / Prolonged Clot Time Profile, Plasma.


An interpretive report will be provided.

Interpretation Provides information to assist in interpretation of the test results

An interpretive report will be provided.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

If the patient's hematocrit is 55% or greater, the volume of citrate anticoagulant should be adjusted prior to submitting the specimen for analysis to avoid dilution of plasma by anticoagulant.(1) 


For optimal results, the patient should not be receiving oral vitamin K inhibitor (eg, warfarin, Coumadin), heparin, low-molecular weight heparin, hirudin (Refludan), argatroban, or fibrinolytic agents (eg, streptokinase, tissue plasminogen activator). If necessary, testing may be performed on patients receiving these treatments. Medications affecting coagulation parameters must be noted on requisition for accurate interpretation of results.


If patient has been recently transfused or will be, it is best to perform this study pretransfusion, if possible.

Clinical Reference Recommendations for in-depth reading of a clinical nature

1. CLSI: Collection, Transport, and Processing of Blood Specimens for Testing Plasma-Based Coagulation Assays and Molecular Hemostasis Assays; Approved Guideline-Fifth Edition. CLSI document H21-A5. Wayne, PA. Clinical and Laboratory Standards Institute; 2008

2. Kamal AH, Tefferi A, Pruthi RK: How to interpret and pursue an abnormal prothrombin time, activated partial thromboplastin time, and bleeding time in adults. Mayo Clin Proc 2007 Jul;82:864-873