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Background Thrombotic thrombocytopenic purpura (TTP) is a rare but potentially fatal disorder caused by ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) deficiency. Prompt identification/exclusion of TTP can thus be facilitated by rapid ADAMTS13 testing. The most commonly utilized (enzyme‐linked immunosorbent assay [ELISA]–based) assay takes several hours to perform and so does not generally permit rapid testing. Objectives To evaluate the utility of a new automated test for ADAMTS13 activity, the HemosIL AcuStar ADAMTS13 Activity assay, based on chemiluminescence and able to be performed on an ACL AcuStar instrument within 33 minutes. Patients/Methods This multicenter (n = 8) assessment included testing of more than 700 test samples, with similar numbers of prospective (n = 348) and retrospective (n = 385) samples. The main comparator was the Technozym ADAMTS13 Activity ELISA. We also assessed comparative performance for detection of ADAMTS13 inhibitors using a Bethesda assay. Results Overall, the chemiluminescent assay yielded similar results to the comparator ELISA, albeit with slight negative bias. ADAMTS13 inhibitor detection was also comparable, albeit with slight positive bias with the AcuStar assay. Assay precision was similar with both assays, and we also verified assay normal reference ranges. Conclusions The HemosIL AcuStar ADAMTS13 Activity assay provided results rapidly, which were largely comparable with the Technozym ADAMTS13 Activity ELISA assay, albeit lower on average. Conversely, inhibitor levels tended to be identified at a higher level on average. Thus, the HemosIL AcuStar ADAMTS13 Activity assay provides a fast and accurate means to quantitate plasma levels of ADAMTS13 for TTP/ADAMTS13 identification/exclusion, and potentially also for other applications.

Aspirin nonadherence and its associated increase in cardiovascular and cerebrovascular events is well described; however, the prevalence of aspirin nonadherence among high-risk pregnant women at risk of preeclampsia and its influence on clinical outcomes remains unclear. Our study examined the prevalence of aspirin nonadherence and resistance among high-risk pregnant women quantitatively (platelet function analyzer 100 and plasma salicylic acid) and clinical outcomes relative to adherence. High-risk pregnant women were recruited across 3 centers in the South West Sydney Local Health District. Simultaneous clinic data, blood sample, and self-reported adherence assessment were prospectively collected at 4-week intervals from 12 to 36 weeks of gestation. Nonadherence was defined as normal platelet function analyzer 100 and nondetectable plasma salicylic acid in <90% of time points. Value of <90% is based on current data. Two hundred twenty women were recruited over 25 months. No woman was aspirin resistant, and 63 (44%) women demonstrated inadequate adherence. Women with inadequate adherence had higher incidence of early-onset preeclampsia (17% versus 2%; odds ratio [OR], 1.9 [95% CI, 1.1–8.7]; P =0.04), late-onset preeclampsia (41% versus 5%; OR, 4.2 [95% CI, 1.4–19.8]; P =0.04), intrauterine growth restriction (29% versus 5%; OR, 5.8; [95% CI, 1.2–8.3]; P =0.001), preterm delivery (27% versus 10%; OR, 5.2 [95% CI, 1.5–8.7]; P =0.008), and higher likelihood of increase in antihypertensives antenatally (60% versus 10%; OR, 4.6 [95% CI, 1.2–10.5]; P =0.003). Kaplan-Meier analysis demonstrated lower incidence of premature delivery in the ≥90% adherent group (HR, 0.3 [95% CI, 0.2–0.5]; P <0.001).Kappa coefficient agreement between qualitative and quantitative assessment of adherence was moderate (κ=0.48; SE=0.029; P <0.0001). Our data demonstrates that aspirin is an effective prophylactic agent with an absolute risk reduction of 51% (number needed to treat, 2) when adherence is ≥90%, compared with women with inadequate adherence. Women who were <90% adherent had higher rates of preeclampsia, intrauterine growth restriction, preterm delivery, and increase in antenatal antihypertensive requirements. Self-reported adherence does not accurately reflect actual adherence.