Reptilase time interpretation

• A. Reptilase time is not affected by heparin; if TT prolonged but reptilase time is normal, prolongation is due to heparin
• B. Reptilase time is not affected by heparin; if TT prolonged but reptilase time is normal, prolongation is due to heparin
• C. If TT prolonged and reptilase time prolonged, there is a fibrinogen abnormality
• D. If TT is normal, there is a fibrinogen abnormality

Answer: (A)

Reptilase time behaves like thrombin time in converting fibrinogen to fibrin, but it is not inhibited by heparin. That means reptilase time stays normal even when heparin is present, whereas thrombin time (TT) is prolonged by heparin.

So when TT is prolonged and the reptilase time remains normal, the most likely cause of the TT prolongation is heparin contamination or lingering heparin effect in the sample. If the reptilase time were also prolonged, that would point more toward a true fibrinogen abnormality (low level or dysfunctional fibrinogen) rather than heparin alone.

In short, the key idea is that reptilase time is not affected by heparin, so a normal reptilase time with a prolonged TT indicates heparin as the culprit.