Highly Accurate Quantitative Analysis Of Enantiomeric Mixtures from Spatially Frequency Encoded ¹H NMR Spectra

We propose an original concept to measure accurately enantiomeric excesses on proton NMR spectra, which combines high-resolution techniques based on a spatial encoding of the sample, with the use of optically active weakly orienting solvents. We show that it is possible to simulate accurately dipolar edited spectra of enantiomers dissolved in a chiral liquid crystalline phase, and to use these simulations to calibrate integrations that can be measured on experimental data, in order to perform a quantitative chiral analysis. This approach is demonstrated on a chemical intermediate for which optical purity is an essential criterion. We find that there is a very good correlation between the experimental and calculated integration ratios extracted from G-SERF spectra, which paves the way to a general method of determination of enantiomeric excesses based on the observation of ¹H nuclei

Simultaneous Determination of All Forms of Biopterin and Neopterin in Cerebrospinal Fluid

In humans, genetic defects of the synthesis or regeneration of tetrahydrobiopterin (BH4), an essential cofactor in hydroxylation reactions, are associated with severe neurological disorders. The diagnosis of these conditions relies on the determination of BH4, dihydrobiopterin (BH2), and dihydroneopterin (NH2) in cerebrospinal fluid (CSF). As MS/MS is less sensitive than fluorescence detection (FD) for this purpose, the most widely used method since 1980 involves two HPLC runs including two differential off-line chemical oxidation procedures aiming to transform the reduced pterins into their fully oxidized fluorescent counterparts, biopterin (B) and neopterin (N). However, this tedious and time-consuming two-step indirect method underestimates BH4, BH2, and NH2 concentrations. Direct quantification of BH4 is essential for studying its metabolism and for monitoring the efficacy of BH4 supplementation in patients with genetic defects. Here we describe a single step method to simultaneously measure BH4, BH2, B, NH2, and N in CSF by HPLC coupled to FD after postcolumn coulometric oxidation. All target pterins were quantified in CSF with a small volume (100 μL), and a single filtration step for sample preparation and analysis. As compared to the most widely used method in more than 100 CSF samples, this new assay is the easiest route for accurately determining in a single run BH4, BH2, and NH2 in CSF in deficit situations as well as for monitoring the efficacy of the treatment

ASH ISTH NHF WFH 2021 guidelines on the diagnosis of von Willebrand disease

Background: von Willebrand disease (VWD) is the most common inherited bleeding disorder known in humans. Accurate and timely diagnosis presents numerous challenges.Objective: These evidence-based guidelines of the American Society of Hematology (ASH), the International Society on Thrombosis and Haemostasis (ISTH), the National Hemophilia Foundation (NHF), and the World Federation of Hemophilia (WFH) are intended to support patients, clinicians, and other health care professionals in their decisions about VWD diagnosis.Methods: ASH, ISTH, NHF, and WFH established a multidisciplinary guideline panel that included 4 patient representatives and was balanced to minimize potential bias from conflicts of interest. The Outcomes and Implementation Research Unit at the University of Kansas Medical Center (KUMC) supported the guideline-development process, including performing or updating systematic evidence reviews up to 8 January 2020. The panel prioritized clinical questions and outcomes according to their importance for clinicians and patients. The panel used the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach, including GRADE Evidence-to-Decision frameworks, to assess evidence and make recommendations, which were subsequently subject to public comment.Results: The panel agreed on 11 recommendations.Conclusions: Key recommendations of these guidelines include the role of bleeding-assessment tools in the assessment of patients suspected of VWD, diagnostic assays and laboratory cutoffs for type 1 and type 2 VWD, how to approach a type 1 VWD patient with normalized levels over time, and the role of genetic testing vs phenotypic assays for types 2B and 2N. Future critical research priorities are also identified.</p

Von Willebrand factor levels in the diagnosis of von Willebrand disease: a systematic review and meta-analysis.

Von Willebrand Disease (VWD) is associated with significant morbidity as a result of excessive mucocutaneous bleeding symptoms. Patients with VWD can experience easy bruising, epistaxis, gastrointestinal and oral cavity bleeding, as well as heavy menstrual bleeding and bleeding after dental work, surgical procedures, and childbirth. Early diagnosis and treatment is important to prevent and treat these symptoms. We systematically reviewed the accuracy of diagnostic tests using different cut-off values of VWF:Ag and platelet-dependent VWF activity assays in the diagnosis of VWD. We searched Cochrane Central, MEDLINE, and EMBASE for eligible studies. Two investigators screened and abstracted data. Risk of bias was assessed using QUADAS-2 and certainty of evidence using the GRADE framework. We pooled estimates of sensitivity and specificity and reported patient important outcomes when relevant. This review included 21 studies that evaluated VWD diagnosis, including the approach to patients with VWF levels that have normalized with age (6 studies), VWF cut-off levels for the diagnosis of Type 1 VWD (9 studies), and platelet-dependent VWF activity/VWF:Ag ratio cut-off levels for the diagnosis of Type 2 VWD (6 studies). The results showed low certainty in the evidence for a net health benefit from reconsidering the diagnosis of VWD versus simply removing the disease in patients with VWF levels that have normalized with age. For the diagnosis of Type 1 VWD, in patients with VWF:Ag <0.30 IU/mL, VWF sequence variants were detected in 75-82% of patients in 2 studies, and for VWF:Ag between 0.30-0.50 IU/mL, VWF sequence variants were detected in 44-60% of patients in 3 studies. A sensitivity of 0.90 (95% CI: 0.83 to 0.94), and a specificity of 0.91 (95% CI: 0.76 to 0.97) were observed for a platelet-dependent VWF activity /VWF:Ag ratio of <0.7 in detecting type 2 VWD (moderate certainty in the test accuracy results). VWF antigen and platelet-dependent activity are continuous variables with an increase in bleeding risk with decreasing levels. This systematic review shows that using a VWF activity/VWF:Ag ratio of <0.7 versus lower cutoff levels in patients with an abnormal initial VWD screen is more accurate for the diagnosis of type 2 VWD

Laboratory assays of VWF activity and use of desmopressin trials in the diagnosis of VWD: a systematic review and meta-analysis.

Von Willebrand Disease (VWD) is associated with significant morbidity because of excessive bleeding. Early diagnosis and treatment is important to prevent and treat these symptoms. We systematically reviewed the accuracy of any VWF activity assay in the diagnosis and classification of patients for VWD. We searched Cochrane Central, MEDLINE, and EMBASE for eligible studies. Risk of bias was assessed using QUADAS-2 and certainty of evidence using the GRADE framework. We pooled estimates of sensitivity and specificity. The review included 77 studies that evaluated the use of newer tests of VWF platelet binding activity (VWF:GPIbR , VWF:GPIbM) and VWF:RCo for the diagnosis of VWD (13 studies), VWF propeptide to VWF:Ag ratio and desmopressin trial for the diagnosis of type 1C VWD (5 studies), VWF multimer analysis and VWF:CB/VWF:Ag ratio for the classification of type 2 VWD (11 studies), genetic testing and ristocetin-induced platelet aggregation to diagnose type 2B VWD (14 studies), genetic testing and FVIII:VWF binding to diagnose type 2N VWD (17 studies). Based on available diagnostic test accuracy, there appears to be comparable test accuracy results between newer tests of platelet binding activity of VWF function and VWF:RCo. The findings of these reviews support VWF multimer analysis or VWF:CB/VWF:Ag to diagnose type 2 VWD. The desmopressin trial test with 1- and 4-hour postinfusion blood work is the test of choice to confirm increased VWF clearance in patients with VWD suspected of type 1C. Additionally, genetic testing is most useful in diagnosing type 2B VWD and has a role in the diagnostic algorithm of suspected type 2N VWD

von Willebrand disease: proposing definitions for future research

von Willebrand disease (VWD) is a common bleeding disorder, which affects 1 in 100 individuals based on laboratory testing and at least 1 in 1000 individuals based on presence of abnormal bleeding symptoms.1,2 VWD was first described almost 100 years ago, and since the initial report, major advances in both diagnostic testing and treatment options have improved outcomes for patients living with VWD; however, many patients still experience significant complications and barriers to treatment. An underlying problem is the lack of consistent unified definitions. In recent work developing evidence-based guidelines for VWD,3,4 it was noted that studies on VWD often used varying definitions. For example, studies of von Willebrand factor (VWF) concentrates did not have consistent definitions for major bleeding, studies on VWF prophylaxis did not use consistent definitions of what constituted a prophylaxis regimen, and studies on desmopressin did not use consistent definitions of desmopressin responsiveness. In addition, common bleeding conditions, such as heavy menstrual bleeding (HMB) and postpartum hemorrhage are variably defined. Such inconsistencies in describing study regimens and endpoints hinder the ability to compare study outcomes and to advance treatment of patients with VWD. We propose definitions for future use in VWD research to facilitate comparison of treatment options. These definitions are based on the most common usage in the literature and endeavor to encompass the most common situations in VWD. The proposed definitions were derived from existing literature and discussed at the first in-person meetings of the guideline panels. Group members made amendments, and the consensus document was circulated to the group. All authors approved the final document