From the Research
For a patient with severe thrombocytopenia and a new rash, the most critical initial step is to order a complete blood count with peripheral blood smear to assess for schistocytes, which are indicative of TTP, and to initiate testing for ADAMTS13 activity and inhibitor testing, as a severely reduced ADAMTS13 activity (<10%) is diagnostic for TTP 1. The patient's presentation with severe thrombocytopenia (platelet count of 16,000) and a new rash necessitates immediate differentiation between immune thrombocytopenic purpura (ITP) and thrombotic thrombocytopenic purpura (TTP) due to their distinct management approaches and potential for severe morbidity and mortality. Key tests to order include:
- Complete blood count with peripheral blood smear to assess for schistocytes
- ADAMTS13 activity and inhibitor testing
- Renal function tests (BUN, creatinine)
- Liver function tests
- Coagulation studies (PT, PTT, fibrinogen)
- Lactate dehydrogenase (LDH)
- Reticulocyte count and direct Coombs test to evaluate for hemolysis Considering the most recent and highest quality evidence, the approach outlined is supported by studies such as 2 and 3, which emphasize the importance of prompt and accurate diagnosis in guiding treatment for thrombocytopenia. Given the potential for TTP, which requires emergency plasma exchange therapy, and the different management strategies for ITP, including corticosteroids, IVIG, or thrombopoietin receptor agonists, it is crucial to prioritize these diagnostic steps to ensure appropriate and timely treatment, thereby optimizing outcomes in terms of morbidity, mortality, and quality of life.