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

ABSTRACT: BACKGROUND:The ADAMTS13 test distinguishes thrombotic thrombocytopenic purpura (TTP) from other thrombotic microangiopathies (TMAs). The 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. STUDY DESIGN AND METHODS:A CEA model was created to compare four scenarios for patients with TMAs, utilizing either an in-house or a send-out ADAMTS13 assay with or without prior risk stratification using PLASMIC scoring. Model variables, 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- to 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- to 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 further 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.

SUBMITTER: Kim CH

PROVIDER: S-EPMC5673545 | biostudies-literature | 2017 Nov

REPOSITORIES: biostudies-literature

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

Kim Chong H CH Kim Chong H CH Simmons Sierra C SC Williams Lance A LA Staley Elizabeth M EM Zheng X Long XL Pham Huy P HP

Transfusion 20170623 11

<h4>Background</h4>The ADAMTS13 test distinguishes thrombotic thrombocytopenic purpura (TTP) from other thrombotic microangiopathies (TMAs). The 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 practic ...[more]

PMID: 28646526

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Project description:BackgroundAcquired thrombotic thrombocytopenic purpura (TTP) is an autoimmune disease in which anti-ADAMTS13 autoantibodies cause severe enzyme deficiency. ADAMTS13 deficiency causes the loss of regulation of von Willebrand factor multimeric size and platelet-tethering function, which results in the formation of disseminated microvascular platelet microthrombi. Precisely how anti-ADAMTS13 autoantibodies, or antibody subsets, cause ADAMTS13 deficiency (ADAMTS13 activity generally < 10%) has not been formally investigated.MethodsWe analysed 92 acquired TTP episodes at presentation, through treatment and remission/relapse using epitope mapping and functional analyses to understand the pathogenic mechanisms of anti-ADAMTS13 IgG.Results89/92 of TTP episodes had IgG recognising the ADAMTS13 N-terminal domains. The central spacer domain was the only N-terminal antigenic target detected. 38/92 TTP episodes had autoantibodies recognising the N-terminal domains alone; 54/92 TTP episodes also had antibodies against the ADAMTS13 C-terminal domains (TSP2-8 and/or CUB domains). Changes in autoantibody specificity were detected in 9/16 patients at relapse, suggesting a continued development of the disease. Functional analyses on IgG from 43 patients revealed inhibitory IgG were limited to anti-spacer domain antibodies. However, 15/43 patients had autoantibodies with no detectable inhibitory action and as many as 32/43 patients had autoantibodies with inhibitory function that was insufficient to account for the severe deficiency state, suggesting that in many patients there is an alternative pathogenic mechanism. We therefore analysed plasma ADAMTS13 antigen levels in 91 acquired TTP presentation samples. We demonstrated markedly reduced ADAMTS13 antigen levels in all presentation samples, median 6% normal (range 0-47%), with 84/91 patients having < 25% ADAMTS13 antigen. ADAMTS13 antigen in the lowest quartile at first presentation was associated with increased mortality (odds ratio 5.7).ConclusionsAnti-spacer domain autoantibodies are the major inhibitory antibodies in acquired TTP. However, depletion of ADAMTS13 antigen (rather than enzyme inhibition) is a dominant pathogenic mechanism. ADAMTS13 antigen levels at presentation have prognostic significance. Taken together, our results provide new insights into the pathophysiology of acquired TTP.

Project description:Approximately 40% of patients who survive acute episodes of thrombotic thrombocytopenic purpura (TTP) associated with severe acquired ADAMTS13 deficiency experience one or more relapses. Risk factors for relapse other than severe ADAMTS13 deficiency and ADAMTS13 autoantibodies are unknown. ADAMTS13 autoantibodies, TTP episodes following infection or type I interferon treatment and reported ensuing systemic lupus erythematosus in some patients suggest immune dysregulation. This cross-sectional study asked whether autoantibodies against RNA-binding proteins or peripheral blood gene expression profiles measured during remission are associated with history of prior relapse in acquired ADAMTS13-deficient TTP. Peripheral blood from 38 well-characterized patients with autoimmune ADAMTS13-deficient TTP in remission was examined for autoantibodies and global gene expression. A subset of TTP patients (9 patients, 24%) exhibited a peripheral blood gene signature composed of elevated ribosomal transcripts that associated with prior relapse. A non-overlapping subset of TTP patients (9 patients, 24%) displayed a peripheral blood type I interferon gene signature that associated with autoantibodies to RNA-binding proteins but not with history of relapse. Patients who had relapsed bimodally expressed higher HLA transcript levels independently of ribosomal transcripts. Presence of any one potential risk factor (ribosomal gene signature, elevated HLA-DRB1, elevated HLA-DRB5) associated with relapse (OR = 38.4; p = 0.0002) more closely than any factor alone or all factors together. Levels of immune transcripts typical of natural killer (NK) and T lymphocytes positively correlated with ribosomal gene expression and number of prior episodes but not with time since the most recent episode. Flow cytometry confirmed elevated expression of cell surface markers encoded by these transcripts on T and/or NK cell subsets of patients who had relapsed. These data associate elevated ribosomal and immune transcripts with relapse history in acquired, ADAMTS13-deficient TTP.

Dataset Information

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

Publications

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

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