Q. A ten-year old girl gets admitted to the hospital with excessive bleeding after an ordinary cut from her forearm. She is hemodynamically stable.
On investigation, she is found to have prolonged PT, PTT and Thrombin time. Normal plasma is added to patient's plasma in 1:1 ratio, but the clotting time does not get corrected. Retiplase time is also prolonged.
The most likely cause is
1. Hemophilia
2. Heparin contamination of sample
3. Lupus anticoagulant
4. Antibody to clotting factor
5. Platelet function defect
Explanation: As explained in a previous section, the causes of failure to correct
on mixing studies are heparin contamination of sample, lupus anticoagulant, and presence
of antibody to a specific clotting factor. Retiplase time rules out
heparin contamination of sample. In lupus anticoagulant, there is usually
absence of clinical bleeding, hypercoagulability and repeated spontaneous abortions,
with similar laboratory profile.
Key points to take home are:
1. Coagulation defects due to deficiency of a clotting factor correct on mixing studies but do not correct if there is an antibody.
2. Heparin behaves like an antibody but Retiplase test does not get affected by it.