This patient presented with this rash on his body.

Of the following tests, which one is most likely to be abnormal in him?

APTT (Activated partial thromboplastin time)

PT (prothrombin time)

Platelet count

Factor 5 level (Leiden)

Protein C & S level

The Answer is Platelet count.
The objective of this question was to differentiate coagulation disorders from bleeding disorders.
Explanation:
This is a picture showing petichiae.
All disorders of coagulation factors will display prolonged coagulation times (either one or both PT & PTT - the only exception is vWf - Von Willebrand factor where there is prolongation of bleeding time and maybe PTT but not PT ). When the APTT or PT is prolonged, one sees ecchymoses and deep bleeding e.g. Hemarthroses or muscle bleeding with hematomas. Most people with petichiae or purpura on the other hand like this case will have problems of platelets or vasculitis. Their bleeding time will be abnormal but coagulation parameters will be normal (compare with Von Willebrands disease).