Bleeding disorders platelet disorders ddx

What is the clinical significance of a platelet count of less than 50,000 per microliter?

1: It confirms a diagnosis of TTP.
2: It is defined as severe thrombocytopenia that raises concern for uncontrollable bleeding.
3: It is an indication for immediate platelet transfusion.
4: It indicates the presence of petechiae on the soles of the feet.