Background: ADAMTS13 activity is a unique marker for thrombotic thrombocytopenic purpura (TTP). Thus, laboratory assays must be especially accurate and precise in the pathological range (below 0.1IU/mL). Additionally, a rapid TTP diagnostic improves patient management and clinical outcomes, which is a challenge with most currently available assays. The automated method presented herein will help the clinician to easily and accurately assess ADAMTS13 activity in 25 minutes.

Aims: To demonstrate the performance characteristics of a rapid and fully quantitative automated ADAMTS13 activity assay suitable for use in routine laboratories.

Methods: The ADAMTS13 activity of 35 samples, including 2 TTP cases and 2 ADAMTS13 depleted plasmas, was assessed using a chromogenic ELISA method and the new automated method employing a lyophilized FRETS-VWF73 Fluorescence-Quenching Substrate on the new automated analyzer.

Results: Calibrators supplied with the assay span the range 0.0-1.01 IU/mL and are traceable to WHO international standard 12/252. Using samples with ADAMTS13 activity above 1.01IU/mL diluted in ADAMTS13 deficient plasma, linearity of the calibration curve within and beyond that range was calculated as >98%. The analytical sensitivity of the assay exhibited a LOB of 0 IU/mL and the LOD at 0.008 IU/mL using the standard assay sample dilution.
Correlation of the automated FRETS assays with the established ELISA assay for 35 samples was linear (r>0.95) with an intercept of < 0.01IU/mL. Samples with an activity above the 1,01IU/mL were diluted with an ADAMTS13 deficient plasma..Using samples with level spanning the measuring range 0.02-1.01IU/mL, imprecision was determined to be < 5%.

Conclusions: This performance evaluation study evidences that the FRETS assay performed on the automated analyzer enables quick and accurate assessment of ADAMTS13 activity levels suitable for use in clinical diagnostic laboratories.

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ISTH Congress Abstracts - https://abstracts.isth.org/abstract/performance-evaluation-of-a-new-fully-automated-fluorogenic-adamts13-activity-assay/