Acute thrombotic thrombocytopenic purpura in Louisiana: Seasonal distribution and evaluation of an ADAMTS13 order screening protocol.

BACKGROUND: Thrombotic thrombocytopenic purpura (TTP) is a life-threatening disorder caused by inactivation of ADAMTS13. It is characterized by thrombocytopenia and microangiopathic hemolytic anemia. Previous studies have produced conflicting data regarding seasonal association of TTP diagnoses. This study evaluated the seasonal distribution of acute TTP in southern Louisiana. Additionally, this study timeline overlapped with the initiation of a new screening protocol for ADAMTS13 testing. STUDY DESIGN AND METHODS: A retrospective analysis of patients receiving ADAMTS13 testing at Ochsner Medical Center from January 2010 to December 2017 was performed. TTP patient episodes were defined by ADAMTS13 activity <10%. Episodes were plotted according to season of presentation and a chi-square analysis was performed. Data of identified TTP patients was analyzed to evaluate for confounding variables. ADAMTS13 order volumes and results before and after screening protocol implementation were compared. RESULTS: Two hundred and fifty-two ADAMTS13 tests were ordered on 245 unique patients. Twenty-five patients had ADAMTS13 activity <10%. No significant differences in seasonal TTP case distribution were identified. Patients with confirmed TTP were younger and more likely to be Black or African American. A screening protocol did not decrease the number of annual ADAMTS13 test orders in our time frame, but was associated with a nonsignificant increase in the percentage of positive results. CONCLUSION: No significant seasonal distribution of TTP was identified in our population. This analysis provides previously unexamined regional information regarding this diagnosis. The number of tests ordered after the implementation of the screening protocol increased, corresponding with our facility's expanding reach.