Patterns of platelet response in idiopathic TTP/HUS: frequency of declining platelet counts with plasma exchange and the recognition and significance of a pseudo refractory state.

For thrombotic thrombocytopenic purpura (TTP), daily plasma exchange (TPE) is typically discontinued when the platelet count normalizes (>150 x 10(9)/L). We observed a decline in platelet count during TPE and in patients who appeared pseudo-refractory because of a platelet count plateau (100-150 10(9)/L range). In the present study, we evaluated platelet count trends in TTP patients. Retrospective review of TTP patients from 01/1999 to 12/2004 was completed. Patients were categorized based on platelet count trends: Group I, counts rose then decreased to levels <100 x 10(9)/L; Group II, counts declined following TPE initiation; Group III, counts rose continuously; Group IV, counts decreased after the count was >100 x 10(9)/L. Additionally, we identified pseudo-refractory patients caused by a platelet count plateau (>100 x 10(9)/L but <150 x 10(9)/L). We identified 60 TTP patients. Within Group I (17 patients/17 series/19.1% of total), the mean decrease in platelet count was 67.3% +/- 22.1% following initial rise. Within Group II (24 patients/25 series/28.1% of total), the mean decrease was 28% +/- 5.3% following presentation. Group III included 31 patients/39 series (43.8% of the total). Within Group IV (seven patients/eight series/9.0% of total), the mean decrease was 17.4% +/- 12.6% following a sustained rise >100 x 10(9)/L. With a declining platelet count and daily TPE, it is generally sufficient to stay the course and the decline will reverse. Our limited experience with pseudo-refractory patients supports discontinuing TPE when counts plateau between 100 and 150 x 10(9)/L when a therapy goal is a platelet count of 150 x 10(9)/L. Recognition of this pseudo-refractory state can minimize the risks of prolonged TPE and the risks of adjunct interventions.

Duke Scholars

Author Nicholas Bandarenko III Pathology