Inverse probability of treatment weighting (IPTW), which has been used to estimate average treatment effects (ATE) using observational data, tenuously relies on the positivity assumption and the correct specification of the treatment assignment model, both of which are problematic assumptions in many observational studies. Various methods have been proposed to overcome these challenges, including truncation, covariate-balancing propensity scores, and stable balancing weights. https://www.selleckchem.com/Akt.html Motivated by an observational study in spine surgery, in which positivity is violated and the true treatment assignment model is unknown, we present the use of optimal balancing by kernel optimal matching (KOM) to estimate ATE. By uniformly controlling the conditional mean squared error of a weighted estimator over a class of models, KOM simultaneously mitigates issues of possible misspecification of the treatment assignment model and is able to handle practical violations of the positivity assumption, as shown in our simulation study. Using data from a clinical registry, we apply KOM to compare two spine surgical interventions and demonstrate how the result matches the conclusions of clinical trials that IPTW estimates spuriously refute. This validation study investigated a flow cytometric apoptosis assay according to good manufacturing practice (GMP). Extracorporeal photopheresis (ECP) is a treatment for various immunological diseases and cutaneous T-cell lymphomas. It is based on the induction of apoptosis by 8-methoxypsoralene and ultraviolet A light. The quantification of apoptosis is therefore essential for ECP improvements. However, despite numerous publications on apoptosis, validated technical details are lacking. Mononuclear cells were collected by apheresis and treated by ECP or camptothecin. Samples taken before and after ECP were cultured for 24, 48 and 72 h and analysed for apoptosis and viability of T cells and monocytes by flow cytometry with Annexin V and 7-AAD staining. Accuracy of the assay, intra- and inter-assay precision and the pre-analytical and analytical stability of the analytes were the investigated parameters. Our data indicate that the median intra- and inter-assay precision coefficient of variation for T cells was 3.86% and 4.80%, respectively. Pre-analytical stability of T cells and monocytes was ensured during short-term storage for up to 2 h on ice. After staining, analytical stability was limited to 30 min, likely because of ongoing apoptosis and loss of monocytes due to plastic adhesion. The results of this validation study show that the assay is GMP-compliant and that its reliability, accuracy and precision are acceptable. While pre-analytical stability of the cells was compatible with on-site procedures, our analytical stability data indicate that this assay is not suited for batch mode analysis of ECP products. The results of this validation study show that the assay is GMP-compliant and that its reliability, accuracy and precision are acceptable. While pre-analytical stability of the cells was compatible with on-site procedures, our analytical stability data indicate that this assay is not suited for batch mode analysis of ECP products. The purpose of this study was to investigate the diagnostic potential of the aortic closure (A2) signal length on Doppler echocardiography in distinguishing aortic patient-prosthesis mismatch (PPM) from prosthetic stenosis among patients with elevated gradients over bioprosthetic valves. The A2 signal length was retrospectively measured for 150 patients with bioprosthetic aortic valves (50 with PPM, 50 with prosthetic stenosis, and 50 with normally functioning valves) from transthoracic echocardiograms performed at NYU Langone Health between 01/01/2012 and 08/01/2018. Mean A2 signal length was shorter among patients with PPM (11.1 ms ± 5.2 ms), than among those with prosthetic stenosis (21.1 ms ± 6.0 ms), P < .001 and controls (21.7 ms ± 7.4 ms), P < .001. There was no difference in A2 signal length between prosthetic stenosis and controls. The A2 signal length yielded an AUC of 0.89 (95% CI 0.82-0.95) for predicting PPM over prosthetic stenosis. Among patients with bioprosthetic aortic valves, the length of the A2 signal on Doppler echocardiography is shorter in PPM than in prosthetic stenosis and normally functioning valves. The A2 signal length may represent a novel metric to distinguish PPM from prosthetic stenosis. Among patients with bioprosthetic aortic valves, the length of the A2 signal on Doppler echocardiography is shorter in PPM than in prosthetic stenosis and normally functioning valves. The A2 signal length may represent a novel metric to distinguish PPM from prosthetic stenosis.We read with interest the paper by Hundt et al. describing the behaviour of common liver tests in COVID-19 and their association with poor outcomes (1). Among presented data, we were surprised to see that serum albumin (ALB) concentrations during hospitalization did not significantly predict patient death at the multivariate analysis (MA), even if 86.6% of patients showed ALB values less then 35 g/L, i.e. the lower reference limit. In a similar COVID-19 population enrolled in our national reference center for infectious diseases, we recently analysed a group of common biochemistry tests, including ALB, as major predictor of COVID-19 severity (2). Although the patient rate showing an ALB less then 35 g/L was quite similar (89%) to that of Hundt's study, at MA low ALB concentrations remained significantly associated (P=0.003) with higher odds of death, ALB values ≤18 g/L giving a positive likelihood ratio of 12.2 for predicting in-hospital death. In terms of absolute ALB levels in the respective populations, as due to spuriously higher ALB values measured with non-specific methods in the evaluated COVID-19 patients. The accuracy of ALB methods may become critical in COVID-19 cases, where ALB is decreased but acute-phase proteins are increased, and thus use of immunological assays should be preferred in this condition (4). The frozen elephant trunk (FET) procedure became a popular entity for utilization in aortic arch aneurysm disease. However, its proper mortality and morbidities as well as the predictors of outcomes are poorly identified. This systematic review and meta-analysis explore FET outcomes and its predictors with a focus on zone aortic proximalization. We searched PubMed/MEDLINE, EMBASE, and Scopus databases from their beginning to June 2020 to find studies reporting the outcomes of the FET procedure for the total arch replacement (TAR). A total of 64 studies including 7967 patients were evaluated. The pooled estimates of cerebrovascular accidents, paraplegia, renal failure, and in-hospital mortality were 7.104 (95% confidence interval [CI], 5.691-8.661; I  = 78.53%), 3.465 (95% CI, 2.852-4.136; I  = 15.96), 14.969 (95% CI, 11.361-18.977; I  = 91.26%), and 8.933 (95% CI, 7.128-10.919; I  = 78.51%), respectively. Stratification by the geographical locations and by the aortic pathologies led to lower heterogeneity, but not for renal failure.