Educational Podcast From ARUP Laboratories
LabMind: An Interview With Dr. Karen Moser: Solving Coagulation Mysteries One Patient at a Time
Medical Experts
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Moser

Rodgers III

Smock

Clotting time tests such as prothrombin time (PT) and/or activated partial thromboplastin time (aPTT) are commonly performed in an outpatient or hospital setting to evaluate the hemostatic system for a variety of reasons. 1 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;82(7):864-873. Kruse-Jarres R, Singleton TC, Leissinger CA. Identification and basic management of bleeding disorders in adults. J Am Board Fam Med. 2014;27(4):549-564. Kruse-Jarres R, Singleton TC, Leissinger CA. Identification and basic management of bleeding disorders in adults. J Am Board Fam Med. 2014;27(4):549-564. Hayward CPM. How I investigate for bleeding disorders. Int J Lab Hematol. 2018;40 Suppl 1:6-14.
Quick Answers for Clinicians
Appropriate testing depends on the clinical presentation (bleeding, thrombosis, or asymptomatic presentation), underlying medical conditions and medications, and which clotting times are prolonged (eg, prothrombin time [PT], activated partial thromboplastin time [aPTT]). 2 Kruse-Jarres R, Singleton TC, Leissinger CA. Identification and basic management of bleeding disorders in adults. J Am Board Fam Med. 2014;27(4):549-564.
Anticoagulant medications frequently interfere with coagulation testing. 2 Kruse-Jarres R, Singleton TC, Leissinger CA. Identification and basic management of bleeding disorders in adults. J Am Board Fam Med. 2014;27(4):549-564.
Indications for Testing
Individuals who have been noted to have a prolonged clotting time (based on results of tests such as PT and/or aPTT) should undergo further evaluation if the cause of the prolonged clotting time is uncertain. 2 Kruse-Jarres R, Singleton TC, Leissinger CA. Identification and basic management of bleeding disorders in adults. J Am Board Fam Med. 2014;27(4):549-564.
Laboratory Testing
Initial Testing
Obtaining a CBC with platelet count may be useful (eg, to help identify or exclude quantitative platelet abnormalities). 1 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;82(7):864-873.
- PT, aPTT
- Dilute Russell viper venom time (DRVVT)
- Lupus anticoagulant reflexive testing
- Fibrinogen
- D-dimer
Observed patterns in the initial test results determine which additional or reflexive testing should be performed; these tests may include coagulation factor assays, Bethesda assays, and/or von Willebrand factor testing.
Condition-Specific Testing
Condition-specific testing is preferred in cases of a known coagulation disorder or strong clinical suspicion for a particular disorder. In patients with a bleeding presentation, consider testing for factor deficiencies, such as hemophilia A or B or rare factor deficiencies. The patterns of the PT and aPTT results should guide test selection. 1 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;82(7):864-873.
In patients with a thrombotic presentation, consider lupus anticoagulant testing.
In patients with an asymptomatic presentation, consider lupus anticoagulant testing, testing for factor deficiencies not associated with a bleeding presentation (eg, factor XII, prekallikrein, and high-molecular-weight kininogen [HMWK] deficiencies), and testing for mild factor deficiencies. 1 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;82(7):864-873.
PT | aPTT | Platelet Count | Potential Cause |
---|---|---|---|
↑ | N | N | FVII deficiency or inhibitor; in some cases, warfarin, vitamin K deficiency, liver disease, DIC, or oral direct Xa inhibitors |
N | ↑ | N | Deficiency or inhibitor of intrinsic pathway, eg, FVIII, FIX, FXI (associated with clinical bleeding), or FXII, prekallikrein, HMWK (not associated with clinical bleeding); VWD types with low FVIII activity; heparin; in some cases, oral direct thrombin inhibitor, or lupus anticoagulant in patients with asymptomatic or thrombotic presentation |
↑ | ↑ | N | Warfarin, vitamin K deficiency; liver disease; DIC; high heparin concentration; direct thrombin inhibitor; direct Xa inhibitor; common pathway deficiency versus inhibitor (FII, FV, FX, fibrinogen); rare lupus anticoagulants with hypoprothrombinemia; multiple factor deficiencies |
↑ | ↑ | ↓ | DIC; severe liver disease; rare cases of heparin-induced thrombocytopenia |
N | N | ↓ | Thrombocytopenia (decreased production, increased destruction, or splenic sequestration of platelets) |
N | N | N | Vascular abnormalities; VWD; qualitative platelet disorder; mild factor deficiency; dysfibrinogenemia; FXIII deficiency; fibrinolytic disorders; in some cases, direct oral anticoagulants |
DIC, disseminated intravascular coagulation; F, factor (eg, factor VII, or FVII); N, normal; VWD, von Willebrand disease |
Test Interference
Coagulation tests may be inaccurate in the presence of anticoagulant drugs or other interfering substances. 1 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;82(7):864-873.
ARUP Laboratory Tests
Electromagnetic Mechanical Clot Detection/Immunoturbidimetry/Microlatex Particle-Mediated Immunoassay/Platelet Agglutination/Chromogenic Assay
Electromagnetic Mechanical Clot Detection
Electromagnetic Mechanical Clot Detection
Electromagnetic Mechanical Clot Detection
Immunoturbidimetry
Electromagnetic Mechanical Clot Detection/Chromogenic Assay
References
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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;82(7):864-873.
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Kruse-Jarres R, Singleton TC, Leissinger CA. Identification and basic management of bleeding disorders in adults. J Am Board Fam Med. 2014;27(4):549-564.
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29741250
Hayward CPM. How I investigate for bleeding disorders. Int J Lab Hematol. 2018;40 Suppl 1:6-14.
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Desborough MJ, Keeling DM. How to interpret a prolonged prothrombin time or activated partial thromboplastin time. Br J Hosp Med (Lond). 2013;74(1):C10-C12.
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Levy JH, Szlam F, Wolberg AS, et al. Clinical use of the activated partial thromboplastin time and prothrombin time for screening: a review of the literature and current guidelines for testing. Clin Lab Med. 2014;34(3):453-477.