Risk and prevention of bleeding during anticoagulant treatment

The overall goal of this thesis was to identify patients who are at high risk for major bleedings during anticoagulant treatment and to reduce the number of major bleeds. The first part looks into methodology of observational studies. It shows that biases in observational studies may be an explanation why statins seem to have many unintended effects. The second part looks into bleeding complications and shows that patient with three concomitant anticoagulants experience high major bleeding rates. Also, a study was performed in which plasma and DNA of participants was collected, to identify risk factors for major bleeds in the future. The first results show that damage to vessel walls increases the risk of major bleeding. Interventions to reduce the number of bleeding events were to dose nadroparin od instead of bid. In addition, multi-dose drug dispensing may increase adherence of medication. Also, vitamin K1 tablets are easier to ingest and this thesis shows that the tablets are as effective in reducing the INR as the oral solution.  Federatie Nederlandse Trombosediensten, Dutch Heart Foundation, Koninklijke Nederlandse Maatschappij ter bevordering van de Pharmacie. Stago, Pfizer, Bayer, Chipsoft, Micronic Holding B.V.LUMC / Geneeskund

Multiplexing Biochemical Signals

In this paper we show that living cells can multiplex biochemical signals, i.e. transmit multiple signals through the same signaling pathway simultaneously, and yet respond to them very specifically. We demonstrate how two binary input signals can be encoded in the concentration of a common signaling protein, which is then decoded such that each of the two output signals provides reliable information about one corresponding input. Under biologically relevant conditions the network can reach the maximum amount of information that can be transmitted, which is 2 bits.Comment: 4 pages, 4 figure

Statin use decreases coagulation in users of vitamin K antagonists

Purpose: The purpose of the study is to determine the immediate and long-term effect of statins on coagulation in patients treated with vitamin K antagonists (VKAs). Methods: We selected patients on VKAs of two Dutch anticoagulation clinics who initiated treatment with a statin between 2009 and 2013. Patients who initiated or stopped concomitant drugs that interact with VKAs or were hospitalised during follow-up were excluded. The VKA dosage (mg/day) after statin initiation was compared with the last VKA dosage before the statin was started. Immediate and long-term differences in VKA dosage (at 6 and 12 weeks) were calculated with a paired student t test. Results: Four hund

Rare switching events in non-stationary systems

Physical systems with many degrees of freedom can often be understood in terms of transitions between a small number of metastable states. For time-homogeneous systems with short-term memory these transitions are fully characterized by a set of rate constants. We consider the question how to extend such a coarse-grained description to non-stationary systems and to systems with finite memory. We identify the physical regimes in which time-dependent rates are meaningful, and state microscopic expressions that can be used to measure both externally time-dependent and history-dependent rates in microscopic simulations.Comment: 14 pages, 8 figure

Stability of vitamin K antagonist anticoagulation after COVID-19 diagnosis

Background: Coagulopathy has been reported in severely ill patients with coronavirus disease 2019 (COVID-19). It is unclear whether outpatients with COVID-19 who are treated with vitamin K antagonists (VKAs) have unstable anticoagulation.Objective: To assess the stability of VKA therapy in patients with COVID-19 through a case-crossover study.Methods: Between February and July 2020, we included patients who tested positive for COVID-19 from two anticoagulant clinics in the Netherlands. We collected international normalized ratios (INRs) determined between 26 weeks before infection and 12 weeks after. Time in therapeutic range (TTR) and the variance growth rate ( VGR) were calculated within patients.Results: Fifty-one patients with COVID-19 (mean age, 84 years) were included, of whom 15 (29%) were men. Mean TTR in the 26 weeks before COVID-19 was 80% (95% confidence interval [CI], 75-85) compared to 59% (95% CI, 51-68) in the 6 weeks after infection. Mean TTR difference was-23% (95% CI, -32 to -14) with a time above therapeutic range of 38% (95% CI, 30-47) in the 6 weeks after infection. The TTR rose again to 79% (95% CI, 69-89) between 6 and 12 weeks after infection. Also, VGR increased, with a mean increase of 4.8 (95% CI, 2.1-7.5) in the 6 weeks after infection. In the 26 weeks before infection, we registered 19 of 641 (3%) of INR >= 5.0 compared with 35 of 247 (14%) in the 6 weeks after (risk ratio, 4.4; 95% CI, 2.7-7.3).Conclusions: COVID-19 is associated with a strong decrease in TTR and in therapeutic stability in patients taking VKAs. Additional monitoring in these patients is advised to maximize therapeutic stability.Clinical epidemiolog

Switching from vitamin K antagonists to direct oral anticoagulants: treatment satisfaction and patient concerns

Background Since direct oral anticoagulants (DOACs) have been introduced for treatment and prevention of thromboembolic diseases, patients on vitamin K antagonists (VKA) have to decide whether to remain on VKA or switch to DOAC. The goal of this study was to evaluate treatment satisfaction, preferences, and concerns among those who already have switched from VKA to DOAC.Methods A questionnaire was sent to 2920 former patients of three anticoagulation clinics in the Netherlands, who switched from VKA to DOAC (2016-2017). Questions concerned demographics, treatment satisfaction, concerns, perspectives on antidotes, and monitoring. To identify predictors for being concerned about adverse events, logistic regression was used to estimate crude- and adjusted (age and sex) odds ratios (OR) and 95% confidence intervals (95% CI).Results One thousand, three hundred ninety-nine questionnaires (response rate 48%) were used for analysis. DOAC treatment satisfaction was high (mean 8.8 of a maximum 10-point score). A quarter of patients expressed concerns about adverse events. Predictors for being concerned were age 75 years, OR 4.1, 95% CI 2.6-6.4), female sex (OR 1.3, 95% CI 1.0-1.6), and high education (OR 1.6, 95% CI 1.2-2.2). Fifty-nine percent of all patients indicated antidote availability as important, 73% would be willing to participate in DOAC monitoring.Conclusions DOAC treatment satisfaction was high. A substantial number of patients expressed concerns about adverse events, especially women, patients aged < 60 years, or highly educated patients. Our findings among patients who already had switched to DOAC may assist in the process of shared decision-making when switching a patient from VKA to DOAC is considered.Thrombosis and Hemostasi

Self-reported therapy adherence and predictors for nonadherence in patients who switched from vitamin K antagonists to direct oral anticoagulants

BackgroundMany patients who used vitamin K antagonists (VKAs) for long-term prevention of thromboembolism are now actively switched to a direct oral anticoagulant (DOAC). Strict adherence to a DOAC is crucial for its success. However, therapy adherence and clinical factors that predict nonadherence are currently not well studied among patients who switched from a VKA to a DOAC.MethodsA questionnaire was developed and sent to 2920 former patients of 3 anticoagulation clinics in the Netherlands, who switched from a VKA to a DOAC between January 2016 and December 2017. Questions concerned demographics, treatment persistence, adherence, and the occurrence of bleeding or thromboembolic events on DOACs. To identify predictors for nonadherence, logistic regression models were used to estimate crude and age/sex-adjusted odds ratios (ORs) and 95% confidence intervals (95% CIs).ResultsA total of 1399 questionnaires (response rate 48%) were used for analysis. DOAC treatment persistence (94%) and adherence (86%) rates were high. Several predictors of nonadherence were identified, including young age (OR, 5.9; 95% CI, 3.6-9.8 for 75 years), low consultation frequency with a specialist (OR, 1.6; 95% CI, 1.1-2.2), a history of minor bleeding on DOACs (OR, 1.9; 95% CI, 1.3-2.8), and a twice-daily dosing regimen (OR, 1.9; 95% CI, 1.3-2.6).ConclusionsSelf-reported treatment persistence and adherence were high in our study population, and several predictors of nonadherence were identified. Factors that can be influenced (low consult frequency with medical specialist, daily dosing regimen) may be used to improve therapy adherence.Thrombosis and Hemostasi

Development of a multivariable prediction model for identification of patients at risk for medication transfer errors at ICU discharge

Introduction Discharge from the intensive care unit (ICU) is a high-risk process, leading to numerous potentially harmful medication transfer errors (PH-MTE). PH-MTE could be prevented by medication reconciliation by ICU pharmacists, but resources are scarce, which renders the need for predicting which patients are at risk for PH-MTE. The aim of this study was to develop a prognostic multivariable model in patients discharged from the ICU to predict who is at increased risk for PH-MTE after ICU discharge, using predictors of PH-MTE that are readily available at the time of ICU discharge. Material and methods Data for this study were derived from the Transfer ICU Medication reconciliation study, which included ICU patients and scored MTE at discharge of the ICU. The potential harm of every MTE was estimated with a validated score, where after MTE with potential for harm were indicated as PH-MTE. Predictors for PH-MTE at ICU discharge were identified using LASSO regression. The c statisticprovided a measure of the overall discriminative ability of the prediction model and the prediction model was internally validated by bootstrap resampling. Based on sensitivity and specificity, the cut-off point of the prediction model was determined. Results The cohort contained 258 patients and six variables were identified as predictors for PH-MTE: length of ICU admission, number of home medications and patient taking one of the following medication groups at home: vitamin/mineral supplements, cardiovascular medication, psycholeptic/analeptic medication and medication for obstructive airway disease. The c of the final prediction model was 0.73 (95%CI 0.67–0.79) and decreased to 0.62 according to bootstrap resampling. At a cut-off score of two the prediction model yielded a sensitivity of 70% and a specificity of 61%. Conclusions A multivariable prediction model was developed to identify patients at risk for PH-MTE after ICU discharge. The model contains predictors that are available on the day of ICU discharge. Once external validation and evaluation of this model in daily practice has been performed, its incorporation into clinical practice could potentially allow institutions to identify patients at risk for PH-MTE after ICU discharge, on the day of ICU discharge, thus allowing for efficient, patient-specific allocation of clinical pharmacy services

Measuring every particle's size from three-dimensional imaging experiments

Often experimentalists study colloidal suspensions that are nominally monodisperse. In reality these samples have a polydispersity of 4-10%. At the level of an individual particle, the consequences of this polydispersity are unknown as it is difficult to measure an individual particle size from microscopy. We propose a general method to estimate individual particle radii within a moderately concentrated colloidal suspension observed with confocal microscopy. We confirm the validity of our method by numerical simulations of four major systems: random close packing, colloidal gels, nominally monodisperse dense samples, and nominally binary dense samples. We then apply our method to experimental data, and demonstrate the utility of this method with results from four case studies. In the first, we demonstrate that we can recover the full particle size distribution {\it in situ}. In the second, we show that accounting for particle size leads to more accurate structural information in a random close packed sample. In the third, we show that crystal nucleation occurs in locally monodisperse regions. In the fourth, we show that particle mobility in a dense sample is correlated to the local volume fraction.Comment: 7 pages, 5 figure