HP and thrombotic thrombocytopenic purpura: If TTP is suspected, the following laboratory tests should be performed: a complete blood count including platelet count, peripheral blood smear, serum chemistry, creatinine, serum LDH, serum bilirubin, haptoglobin, a coagulation profile including PT, activated PTT, fibrinogen, D-dimer levels, Coombs test, and ADAMTS13 activity and inhibitor levels.