Background: Quantifying A disintegrin-like and metalloprotease with thrombospondin type 1 motif, member 13 (ADAMTS-13) activity enhances thrombotic thrombocytopenic purpura (TTP) diagnosis but most assays are time consuming, technically demanding, and mainly available in reference centers.Objective: Evaluate a simple, semiquantitative ADAMTS-13 activity screening test for early identification/exclusion of TTP.Patients/Methods: Plasma from 220 patients with suspected thrombotic microangiopathy at three reference centers were tested with TECHNOSCREEN ® ADAMTS13 activity screening test in comparison with TECHNOZYM ® ADAMTS-13 activity ELISA at two centers, and in-house fluorescence resonance energy transfer assay at the third center. The screening test indicates if ADAMTS-13 activity is at one of four level-indicator points: 0, 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 while 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.
SummaryHeavily calcified annuli increase the incidence of complications after prosthetic valve replacement-heart block, separation of the aorta or the atrium from the ventricle, late aneurysm formation, paravalvular leak, and haemolysis. An ultrasonic calculus-disintegrator has been developed to remove calcific deposits. The instrument is portable, robust, easily sterilized, inexpensive, and provides nebulized water at the ultrasonic tip which keeps the tissues cool, helps to break up the calculus by cavitation, and washes the calcific debris into the sucker. Preliminary trial on excised calcific valves showed the ultrasound instrument to be capable of removing most forms of calcification. In clinical prosthetic replacement of valves it enabled good clearance of the annulus to be performed in six out of seven cases, in one ofwhich earlier operation had been unsuccessful because of calcification. Two elderly patients with pure calcific aortic stenosis were successfully treated by debridement of the aortic valve with ultrasound.
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