ADAMTS13 test and/or PLASMIC clinical score in management of acquired thrombotic thrombocytopenic purpura: a cost‐effective analysis

Abstract

Background ADAMTS13 test distinguishes thrombotic thrombocytopenic purpura (TTP) from other thrombotic microangiopathies (TMAs). PLASMIC score helps determine the pretest probability of ADAMTS13 deficiency. Due to inherent limitations of both tests, and potential adverse effects and cost of unnecessary treatments, we performed a cost-effectiveness analysis (CEA) investigating the benefits of incorporating an in-hospital ADAMTS13 test and/or PLASMIC score into our clinical practice. Methods A CEA model was created to compare 4 scenarios for a patient with TMAs, utilizing either an in-house vs. send-out ADAMTS13 assay with or without prior risk stratification using PLASMIC scoring. Model parameters, including probabilities and costs, were gathered from the medical literature, except for the ADAMTS13 send-out and in-house tests, which were obtained from our institutional data. Results If only the cost is considered, in-house ADAMTS13 test for patients with intermediate-high risk PLASMIC score is the least expensive option ($4,732/patient). If effectiveness is assessed as measured by the number of averted deaths, send-out ADAMTS13 test is the most effective. Considering the cost/effectiveness ratio, the in-house ADAMTS13 test in patients with intermediate-high risk PLASMIC score is the best option, followed by the in-house ADAMTS13 test without the PLASMIC score. Conclusions In patients with clinical presentations of TMAs, having an in-hospital ADAMTS13 test to promptly establish the diagnosis of TTP appears to be cost-effective. Utilizing the PLASMIC score increases the cost-effectiveness of the in-house ADAMTS13 test. Our findings indicate the benefit of having a rapid and reliable in-house ADAMTS13 test, especially in the tertiary medical center.

The importance of clinical judgment for the diagnosis of thrombotic thrombocytopenic purpura

“…These data of Kim and colleagues, together with the data that supported the derivation of the PLASMIC score, are important for clinicians whenever they evaluate a patient for the possible diagnosis of TTP. The decision to begin TPE, or to hesitate, is urgent because of the risk of death if TTP is not treated and the effectiveness of TPE for treatment of TTP .…”

“…In this issue of TRANSFUSION, Kim and colleagues analyze the cost‐effectiveness of different strategies for the initial management of patients with suspected thrombotic thrombocytopenic purpura (TTP) using previously published data. They analyzed four hypothetical scenarios: two different rates of reporting ADAMTS13 activity measurements, each with and without the prior use of a clinical prediction score (the PLASMIC score).…”

“…Scenarios 3 and 4 were the two rates of reporting ADAMTS13 activity combined with the PLASMIC score; the ADAMTS13 test was not performed when the PLASMIC score was less than 4 (maximum score, 7), indicating a low probability of ADAMTS13 activity of less than 10% . Kim and colleagues conclude that an in‐hospital ADAMTS13 test combined with the PLASMIC score provides the most cost‐effective management. Even though there is cost required for the implementation of an in‐hospital ADAMTS13 test, cost saving would result from avoidance of plasma exchange treatment (TPE) for patients with a low probability of TTP (PLASMIC score of 4 or less ADAMTS13 activity ≥ 10%).…”

“…Should TPE be requested immediately or is it better to hesitate and to intensify the search for an alternative diagnosis? How do the data of Kim and colleagues help this decision? Their conclusion that a rapid report of ADAMTS13 activity together with a PLASMIC score provides the most cost‐effective practice may not be the same as providing the most clinically effective practice.…”

“…Now, back to the report by Kim and coworkers . They used data from many published sources (see their Table S1) and they used multiple methods of analysis.…”