Prolonged Clot Time Profile
Determining cause of prolongation of prothrombin time or activated partial thromboplastin time
Screening for prolonged clotting times and determining the presence of factor deficiency(ies) or inhibitor (factor-specific, lupus-like, or the presence of heparin)
Testing Algorithm Delineates situation(s) 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 Russells viper venom time (DRVVT), thrombin time (bovine), fibrinogen, D-dimer, soluble fibrin monomer, and special coagulation interpretation.
If PT is > or =14 seconds, PT mix will be performed.
If APTT is >36 seconds, APTT mix will be performed.
If APTT mix is >36 seconds with no evidence of heparin in samples, platelet neutralization procedure will be performed.
If DRVVT ratio is > or =1.2, DRVVT mix and DRVVT confirmation will be performed.
If thrombin time is >23 seconds, reptilase time will be performed.
If PT, APTT, or DRVVT is prolonged, coagulation factor assays may be performed.
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 work-up as needed to define the abnormality.
Possibilities for a cause of prolongation include:
-Factor deficiency(ies), congenital or acquired
-Factor inhibitors (including Coumadin therapy)
-Dilution of specimen by anticoagulant if patient hematocrit is > or =55%
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.
A 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 patient hematocrit is > or =55%, the volume of citrate anticoagulant should be adjusted prior to submitting the specimen for analysis to avoid dilution of plasma by anticoagulant (see Clinical Reference-NCCLS Document H21-1).
Patient should not be receiving oral vitamin K inhibitor (eg, warfarin, Coumadin), heparin, low molecular weight heparin, hirudin (Refludan), argatroban, fibrinolytic agents (eg, streptokinase, tissue plasminogen activator) for optimal results. 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 Provides recommendations for further in-depth reading of a clinical nature
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