{"id":"aptt","name":"Activated Partial Thromboplastin Time (aPTT)","shortName":"aPTT","aliases":["aPTT","PTT","Activated Partial Thromboplastin Time","Partial Thromboplastin Time","PTT, Activated","aPTT (Seconds)","PTT-A","TTPA","APTT","PTT Activated","Activated PTT","Partial Thromboplastin Time, Activated","Partial Thromboplastin Time (PTT)","PTT, Plasma","APTT, Plasma","Kaolin Cephalin Clotting Time","KCCT"],"abbreviations":["aPTT","APTT","PTT","KCCT"],"loinc":[{"code":"14979-9","primary":true},{"code":"3173-2","primary":false}],"specimen":"plasma","units":[{"ucum":"s","display":"sec"}],"referenceRanges":[{"population":"Adults","low":25,"high":37,"unit":"s","unitDisplay":"sec","note":"Adult interval from Mayo Clinic Laboratories (25–37 seconds). ARUP lists 24–35 seconds. The aPTT depends on the lab's reagent and analyzer, so every lab sets its own interval and the one printed on your report is the one to use. Some countries print an aPTT ratio instead of seconds (see the aPTT ratio marker); the Croatian national recommendations give about 0.8–1.2 for that ratio. This is not a target for heparin treatment: labs are advised to set a heparin range for each reagent and analyzer, for example against anti-Xa activity of about 0.3–0.7 IU/mL. No fasting or special preparation is needed, but a tube that is not filled to the line can change the result.","sources":[{"title":"Activated Partial Thromboplastin Time, Plasma (test APTTP)","url":"https://www.testcatalog.org/show/APTTP","publisher":"Mayo Clinic Laboratories (Extended Catalog)"},{"title":"Partial Thromboplastin Time (ARUP test 0030235)","url":"https://ltd.aruplab.com/Tests/Pub/0030235","publisher":"ARUP Laboratories"},{"title":"Croatian Society of Medical Biochemistry and Laboratory Medicine: National recommendations for blood collection, processing, performance and reporting of results for coagulation screening assays prothrombin time, activated partial thromboplastin time, thrombin time, fibrinogen and D-dimer","url":"https://pubmed.ncbi.nlm.nih.gov/31223257/","publisher":"Biochemia Medica","year":2019}]}],"review":{"status":"ai-verified","label":"AI-verified against cited sources. Awaiting expert review","lastReviewed":"2026-10-03"},"summary":"A clotting-time test that shows how many seconds your blood takes to clot, and is also used to monitor heparin treatment.","url":"https://bloodtesttracker.com/markers/aptt","notice":"Information, not medical advice. Ranges differ between labs, so the range on your own report is the one your result is judged against."}