Laboratory testing to rule out other diagnoses includes the ADAMTS13 enzyme (for thrombotic thrombocytopenic purpura), coagulation studies (for disseminated intravascular coagulation), direct Coombs test (for autoimmune hemolytic anemia), T-cell chimerism (for GVHD), or viral polymerase chain reaction (for infection) [21]. The gene discussed is ADAMTS13; the disease is thrombotic thrombocytopenic purpura.