Test Catalog

Test ID: APROL    
Prolonged Clot Time Profile, Plasma

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)

Testing Algorithm Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

Initial testing includes: prothrombin time (PT), activated partial thromboplastin time (APTT), dilute Russell viper venom time (DRVVT), thrombin time (bovine), fibrinogen, D-dimer, and prolonged clot time interpretation.


If PT is >13.9 seconds, then PT mix will be performed at an additional charge.

If APTT is > or =38 seconds, then APTT mix will be performed at an additional charge.

If APTT mix is > or =38 seconds and thrombin time is <35.0 seconds (no evidence of heparin), then platelet neutralization procedure will be performed at an additional charge.

If DRVVT ratio is > or =1.20, then DRVVT mix and DRVVT confirmation will be performed at an additional charge.

If thrombin time is > or =25.0 seconds, then reptilase time will be performed at an additional charge.

If fibrinogen is <150 mg/dL, or clinically indicated, then PT-fibrinogen will be performed at an additional charge.

If D-dimer is >500 ng/mL FEU, then soluble fibrin monomer will be performed at an additional charge.

If PT, APTT, or DRVVT is prolonged, then coagulation factor assays may be performed at an additional charge.

If factor assay result is below the normal range, the appropriate factor inhibitor screen may be performed along with the Bethesda titering assay, at an additional charge, if inhibitor screen is positive.

If appropriate, Staclot lupus anticoagulant (LA) will be performed at an additional charge to clarify significant abnormalities in the screen test results.

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 validation of the prolongation and as comprehensive a workup as needed to define the abnormality.


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 e.g. factor VIII inhibitors (bleeding disorder)

-Lupus anticoagulant (risk for thrombosis or recurrent miscarriage)

-Anticoagulant drug effect eg, (including warfarin (Coumadin or Jantoven), oral anti-Xa inhibitors, oral direct thrombin inhibitors), 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.

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. Treatment with heparin causes false-positive results of in vitro coagulation testing for lupus anticoagulant. Coumadin treatment may impair ability to detect the more subtle varieties of lupus-like anticoagulants.

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. Clinical and Laboratory Standards Institute; 2008

2. Kamal AH, Tefferi A, Pruthi RK: MBBS. 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

3. Laboratory Hematology Practice. Edited by K Kottke-Marchant. Wiley Blackwell Publishing, 2012

Special Instructions Library of PDFs including pertinent information and forms related to the test