The partial thromboplastin time (PTT) and
activated partial thromboplastin time (APTT) may be normal in people who have
inherited bleeding disorders but have only mild symptoms.
is used to check treatment of people who are using heparin or other
blood-thinning medicine to prevent blood clots.
who use heparin have a higher APTT because of other substances in their blood
and not because of blood-thinning medicines. A test called the heparin
neutralization assay may be done to see if this is true.
blood clotting test, called prothrombin time (PT), measures other clotting
factors. Partial thromboplastin time and prothrombin time are often done at the
same time to check for bleeding problems. For more information, see the topic
An PTT or APTT is done
regularly in people who have bleeding or clotting problems. The tests are also
done before procedures or surgeries where too much bleeding may be a
Other Works Consulted
Chernecky CC, Berger BJ (2008). Laboratory Tests and Diagnostic Procedures, 5th ed. St. Louis:
Fischbach FT, Dunning MB III, eds. (2009).
Manual of Laboratory and Diagnostic Tests, 8th ed.
Philadelphia: Lippincott Williams and Wilkins.
Pagana KD, Pagana TJ (2010). Mosby’s Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier.