A multi‐centre evaluation of TECHNOSCREEN® ADAMTS‐13 Activity assay as a screening tool for detecting deficiency of ADAMTS‐13

BACKGROUND: Quantifying ADAMTS-13 activity enhances thrombotic thrombocytopenic purpura (TTP) diagnosis but most assays are time consuming, technically demanding and mainly available in reference centres. OBJECTIVE: Evaluate a simple, semi-quantitative ADAMTS-13 activity screening test for early identification/exclusion of TTP. PATIENTS/METHODS: Plasmas from 220 patients with suspected thrombotic microangiopathy at three reference centres were tested with TECHNOSCREEN(R) ADAMTS13 Activity screening test in comparison with TECHNOZYM(R) ADAMTS-13 Activity ELISA at two centres, and in-house fluorescence resonance energy transfer assay at the third centre. The screening test indicates if ADAMTS-13 activity is at one of four level-indicator points: zero, 0.1, 0.4 or 0.8 IU/mL. RESULTS: Screen results were interpreted as binary data in that ADAMTS-13 activity was above or below the 0.1 IU/mL TTP clinical threshold. Combining all sites' data, the screen exhibited 88.7% sensitivity, 90.4% specificity, 74.6% positive predictive value and 96.2% negative predictive value, comparable to published data for quantitative assays. Five samples with quantitative results below the threshold gave screen readings of 0.1 IU/mL and seven marginally above the threshold gave screen readings of zero. All would warrant plasma exchange whilst the level is quantified. Nine samples with normal/near normal results gave screens of zero and confirmatory quantifications would prompt early treatment withdrawal, as is current practice. One sample generated screen/quantitative results of 0.4/0.00 IU/mL respectively and was the only clear false-negative. CONCLUSIONS: The screening test provides more rapid ADAMTS-13 level evaluation than most currently available assays. Its simple operation renders it suitable for adoption in routine or specialist laboratory environments.