Utilization and Cost Effectiveness of a Risk Stratified Diagnostic Approach to Patients with Suspected Thrombotic Thrombocytopenic Purpura

Background:Thrombotic thrombocytopenic purpura (TTP) is a rare but deadly thrombotic microangiopathy (TMA) that is caused by an acquired deficiency in the ADAMTS13 enzyme. The PLASMIC clinical scoring system was developed and validated in 2014 by the Harvard TMA Research Collaborative in order to determine the pretest probability of severe ADAMTS13 deficiency in cases of suspected TTP. We studied the role of the PLASMIC score in guiding use of the ADAMTS13 activity assay and assessed the cost effectiveness of a score-based diagnostic approach to patients with TMA compared to two strategies currently in use within our consortium. Methods:We utilized an expanded dataset from the Harvard TMA Research Collaborative consisting of all consecutive cases of TMA at three large academic medical centers for which an ADAMTS13 assay was sent between 2004-2015 (n=647). To investigate trends in ADAMTS13 testing over time, we compared the experience at two centers (A and B) with a liberal ADAMTS13 testing policy against a third center in our consortium (C) that carries a more restrictive policy requiring pre-approval by the blood transfusion service. Cost savings analysis was subsequently performed to assess the potential impact of an algorithm incorporating the PLASMIC score for clinical decision support in the workup of these patients. Results:At Sites A and B, we observed after adjusting for changes in inpatient volume that the quantity of ADAMTS13 tests increased greater than eight-fold during the study period (from 11 per 100,000 admissions in 2004 to 94 per 100,000 admissions in 2015, P Conclusions:Taken together, our results demonstrate that a significant number of patients in our consortium who are at minimal risk for TTP nevertheless undergo ADAMTS13 testing and receive expert consultation and/or TPE. An approach incorporating upfront application of the PLASMIC clinical scoring system to risk stratify patients with suspected TTP may help enhance the cost effectiveness of diagnosing and managing these cases. Figure Figure. Table Table. Disclosures No relevant conflicts of interest to declare.