reptilase time
{{Short description|Laboratory blood test}}
{{Infobox diagnostic
| name = Reptilase time
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| purpose =blood test used to detect deficiency or abnormalities in fibrinogen
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Reptilase time (RT) is a blood test used to detect deficiency or abnormalities in fibrinogen,{{cite journal |vauthors=Van Cott EM, Smith EY, Galanakis DK |title=Elevated fibrinogen in an acute phase reaction prolongs the reptilase time but typically not the thrombin time |journal=American Journal of Clinical Pathology |volume=118 |issue=2 |pages=263–8 |date=August 2002 |pmid=12162688 |doi=10.1309/WUB3-72JT-E50M-EU8J |doi-access=free }}{{cite journal |vauthors=Johnson PJ, White Y, Woolf IL, Williams R |title=Reptilase time in cirrhosis and hepatocellular carcinoma |journal=Br Med J |volume=2 |issue=6091 |pages=869–70 |date=October 1977 |pmid=200301 |pmc=1631704 |doi= 10.1136/bmj.2.6091.869-a}} especially in cases of heparin contamination.
Reptilase, an enzyme found in the venom of Bothrops snakes, has activity similar to thrombin. Unlike thrombin, reptilase is resistant to inhibition by antithrombin III. Thus, the reptilase time is not prolonged in blood samples containing heparin, hirudin, or direct thrombin inhibitors, whereas the thrombin time will be prolonged in these samples. Reptilase also differs from thrombin by releasing fibrinopeptide A, but not fibrinopeptide B, in its cleavage of fibrinogen.{{cn|date=November 2021}}
| class=wikitable
|+ Causes of prolonged thrombin time{{cite web|url=https://www.mayocliniclabs.com/test-catalog/Clinical+and+Interpretive/602185|title=Test ID: RTSC. Reptilase Time, Plasma|website=Mayo Clinic laboratories|access-date=2021-02-25}} ! Reptilase time !! Cause !! Further workup indicated |
| Normal
| Heparin, hirudin, or direct thrombin inhibitor | Human TT and/or heparin assays |
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| rowspan=3| Prolonged
| Hypo- or afibrinogenemia | Fibrinogen quantification |
| Dysfibrinogenemia
| Fibrinogen activity assay |
| Fibrin(ogen) split products (FSP)
| FSP or D-dimer quantification |