Major differences in clinical presentation, diagnosis and management of men and women with autosomal inherited bleeding disorders.

BACKGROUND: In recent years, more awareness is raised about sex-specific dilemmas in inherited bleeding disorders. However, no large studies have been performed to assess differences in diagnosis, bleeding phenotype and management of men and women with bleeding disorders. Therefore, we investigated sex differences in a large cohort of well-defined patients with autosomal inherited bleeding disorders (von Willebrand disease (VWD), rare bleeding disorders (RBDs) and congenital platelet defects (CPDs)). METHODS: We included patients from three nationwide cross-sectional studies on VWD, RBDs and CPDs in the Netherlands, respectively the WiN, RBiN and TiN study. In all studies a bleeding score (BS) was obtained, and patients filled in an extensive questionnaire on the management and burden of their disorder. FINDINGS: We included 1092 patients (834 VWD; 196 RBD; 62 CPD), of whom 665 (60.9%) were women. Women were more often referred because of a bleeding diathesis than men (47.9% vs 36.6%, p = 0.002). Age of first bleeding was similar between men and women, respectively 8.9 ± 13.6 (mean ±sd) years and 10.6 ± 11.3 years (p = 0.075). However, the diagnostic delay, which was defined as time from first bleeding to diagnosis, was longer in women (11.6 ± 16.4 years) than men (7.7 ± 16.6 years, p = 0.002). Similar results were found when patients referred for bleeding were analyzed separately. Of women aging 12 years or older, 469 (77.1%) had received treatment because of sex-specific bleeding. INTERPRETATION: Women with autosomal inherited bleeding disorders are more often referred for bleeding, have a longer diagnostic delay, and often require treatment because of sex-specific bleeding. FUNDING: The WiN study was supported (in part) by research funding from the Dutch Hemophilia Foundation (Stichting Haemophilia), Shire (Takeda), and CSL Behring (unrestricted grant).

Population pharmacokinetics of factor IX in hemophilia B patients undergoing surgery.

Essentials Factor IX (FIX) dosing using body weight frequently results in under and overdosing during surgery. We aimed to establish a population pharmacokinetic (PK) model describing the perioperative FIX levels. Population PK parameter values for clearance and V1 were 284 mL h-170 kg-1 and 5450 mL70 kg-1. Perioperative PK parameters differ from those during non-surgical prophylactic treatment. SUMMARY: Background Hemophilia B is a bleeding disorder characterized by a deficiency of coagulation factor IX (FIX). In the perioperative setting, patients receive FIX concentrates to ensure hemostasis. Although FIX is usually dosed according to bodyweight, under- and overdosing occurs frequently during surgery. Aim The objective was to quantify and explain the interpatient variability of perioperatively administered plasma-derived (pd) and recombinant (r) FIX concentrates. Methods Data were collected from 118 patients (median age, 40 years [range, 0.2-90]; weight, 79 kg [range, 5.3-132]) with moderate (28%) or severe hemophilia B (72%), undergoing 255 surgical procedures. Population pharmacokinetic (PK) parameters were estimated using nonlinear mixed-effect modeling in NONMEM. Results Measured perioperative FIX level vs. time profiles were adequately described using a three-compartment PK model. For a typical 34-year-old patient receiving rFIX, clearance (CL), intercompartmental clearance (Q2, Q3), distribution volume of the central compartment (V1) and peripheral compartments (V2, V3) plus interpatient variability (%CV) were: CL, 284 mL h-170 kg-1 (18%); V1, 5450 mL70 kg-1 (19%); Q2, 110 mL h-170 kg-1; V2, 4800 mL70 kg-1; Q3, 1610 mL h-170 kg-1; V3, 2040 mL70 kg-1. From 0.2 years, CL and V1 decreased 0.89% and 1.15% per year, respectively, until the age of 34 years. Patients receiving pdFIX exhibited a lower CL (11%) and V1 (17%) than patients receiving rFIX. Interpatient variability was successfully quantified and explained. Conclusions The estimated perioperative PK parameters of both pdFIX and rFIX are different from those reported for prophylactic treatment. The developed model may be used to apply PK-guided dosing of FIX concentrates during surgery.

The pediatric acenocoumarol dosing algorithm: the Children Anticoagulation and Pharmacogenetics Study.

Essentials A pediatric pharmacogenetic dosing algorithm for acenocoumarol has not yet been developed. We conducted a multicenter retrospective follow-up study in children in the Netherlands. Body surface area and indication explained 45.0% of the variability in dose requirement. Adding the genotypes of VKORC1, CYP2C9 and CYP2C18 to the algorithm increased this to 61.8%. SUMMARY: Background The large variability in dose requirement of vitamin K antagonists is well known. For warfarin, pediatric dosing algorithms have been developed to predict the correct dose for a patient; however, this is not the case for acenocoumarol. Objectives To develop dosing algorithms for pediatric patients receiving acenocoumarol with and without genetic information. Methods The Children Anticoagulation and Pharmacogenetics Study was designed as a multicenter retrospective follow-up study in Dutch anticoagulation clinics and children's hospitals. Pediatric patients who used acenocoumarol between 1995 and 2014 were selected for inclusion. Clinical information and saliva samples for genotyping of the genes encoding cytochrome P450 (CYP) 2C9, vitamin K epoxide reductase complex subunit 1 (VKORC1), CYP4F2, CYP2C18 and CYP3A4 were collected. Linear regression was used to analyze their association with the log mean stable dose. A stable period was defined as three or more consecutive International Normalized Ratio measurements within the therapeutic range over a period of ≥ 3 weeks. Results In total, 175 patients were included in the study, of whom 86 had a stable period and no missing clinical information (clinical cohort; median age 8.9 years, and 49% female). For 80 of these 86 patients, genetic information was also available (genetic cohort). The clinical algorithm, containing body surface area and indication, explained 45.0% of the variability in dose requirement of acenocoumarol. After addition of the VKORC1, CYP2C9, and CYP2C18 genotypes to the algorithm, this increased to 61.8%. Conclusions These findings show that clinical factors had the largest impact on the required dose of acenocoumarol in pediatric patients. Nevertheless, genetic factors, and especially VKORC1, also explained a significant part of the variability.

Perioperative replacement therapy in haemophilia B: An appeal to "B" more precise.

INTRODUCTION: Haemophilia B is caused by a deficiency of coagulation factor IX (FIX) and characterized by bleeding in muscles and joints. In the perioperative setting, patients are treated with FIX replacement therapy to secure haemostasis. Targeting of specified FIX levels is challenging and requires frequent monitoring and adjustment of therapy. AIM: To evaluate perioperative management in haemophilia B, including monitoring of FIX infusions and observed FIX levels, whereby predictors of low and high FIX levels were assessed. METHODS: In this international multicentre study, haemophilia B patients with FIX < 0.05 IU mL-1 undergoing elective, minor or major surgical procedures between 2000 and 2015 were included. Data were collected on patient, surgical and treatment characteristics. Observed FIX levels were compared to target levels as recommended by guidelines. RESULTS: A total of 255 surgical procedures were performed in 118 patients (median age 40 years, median body weight 79 kg). Sixty percent of FIX levels within 24 hours of surgery were below target with a median difference of 0.22 IU mL-1 [IQR 0.12-0.36]; while >6 days after surgery, 59% of FIX levels were above target with a median difference of 0.19 IU mL-1 [IQR 0.10-0.39]. Clinically relevant bleeding complications (necessity of a second surgical intervention or red blood cell transfusion) occurred in 7 procedures (2.7%). CONCLUSION: This study demonstrates that targeting of FIX levels in the perioperative setting is complex and suboptimal, but although this bleeding is minimal. Alternative dosing strategies taking patient and surgical characteristics as well as pharmacokinetic principles into account may help to optimize and individualize treatment.

Characteristics and quality of oral anticoagulation treatment in pediatric patients in the Netherlands based on the CAPS cohort.

Essentials The knowledge of quality and safety of acenocoumarol and phenprocoumon use in children is limited. We used data from a multicenter retrospective follow-up study in children in the Netherlands. The quality of anticoagulation control in the first month of use was low, but improved thereafter. No thromboembolic events occurred, however bleeding events occurred in 1-3 out of 10 patients. SUMMARY: Background The use of vitamin-K antagonists in pediatric patients is rare and information on the quality and safety of treatment with acenocoumarol and phenprocoumon is limited. Objectives To assess the quality, safety and effectiveness during the first year of acenocoumarol and phenprocoumon treatment in pediatric patients in the Netherlands. Methods The Children Anticoagulation and Pharmacogenetics Study (CAPS) was designed as a multicenter retrospective follow-up study. Patients who used acenocoumarol or phenprocoumon at an age of ≤ 18 years, were selected from four pediatric hospitals and one anticoagulation clinic in the Netherlands. The quality of treatment was assessed by calculating the percentage of time in therapeutic INR range (TTR) for the first month and for every 3 months of use during the first year of treatment. Effectiveness and safety were assessed by the number of thromboembolic and bleeding events. Results In total, 213 patients participated, of whom 187 (155 acenocoumarol; 32 phenprocoumon) were included in this analysis. The mean TTR was 47.0% and 51.4% in the first month of use for acenocoumarol and phenprocoumon, respectively. After the first 3 months the mean TTR for both VKAs was above 64%. In 14.6% (acenocoumarol) and 31.3% (phenprocoumon) of the patients a bleeding event occurred during the first year of treatment; no thromboembolic events were reported. Conclusions The quality of anticoagulation treatment was low during the first month of use and leaves room for improvement. After the first month it increased to an acceptable level. However, bleeding events occurred frequently during the first year.

Relationship between neighborhood socioeconomic status and venous thromboembolism: results from a population-based study.

Essentials Literature on socioeconomic status (SES) and incidence of venous thromboembolism (VTE) is scarce. We assessed neighborhood SES with VTE risk in a population of over 1.4 million inhabitants. Higher neighborhood SES was associated with lower incidence of VTE. These findings are helpful to inform policy and resource allocation in health systems. SUMMARY: Background The association between socioeconomic status and arterial cardiovascular disease is well established. However, despite its high burden of disability-adjusted life years, little research has been carried out to determine whether socioeconomic status is associated with venous thromboembolism. Objective To determine if neighborhood socioeconomic status is associated with venous thromboembolism in a population-based study from the Netherlands. Methods We identified all patients aged 15 years and older with a first event of venous thromboembolism from inhabitants who lived in the urban districts of The Hague, Leiden and Utrecht in the Netherlands in 2008-2012. Neighborhood socioeconomic status was based on the status score, which combines educational level, income and unemployment on a four-digit postal code level. Incidence rate ratios of venous thromboembolism were calculated for different levels of neighborhood socioeconomic status, with adjustments for age and sex. Results A total of 7373 patients with a first venous thromboembolism (median age 61 years; 50% deep vein thrombosis) were identified among more than 1.4 million inhabitants. Higher neighborhood SES was associated with lower incidence of VTE. In the two highest status score groups (i.e. the 95-99th and > 99th percentile), the adjusted incidence rate ratios were 0.91 (95% confidence interval [CI], 0.84-1.00) and 0.80 (95% CI, 0.69-0.93), respectively, compared with the reference status score group (i.e. 30-70th percentile). Conclusions High neighborhood socioeconomic status is associated with a lower risk of first venous thromboembolism.

Major bleeding risks of different low-molecular-weight heparin agents: a cohort study in 12 934 patients treated for acute venous thrombosis.

Essentials Low-molecular-weight-heparins (LMWH) kinetics differ which may result in different bleeding risks. A cohort of 12 934 venous thrombosis patients on LMWH was followed until major bleeding. The absolute major bleeding risk was low among patients registered at the anticoagulation clinic. Once-daily dosing was associated with a lower bleeding risk as compared with twice-daily. SUMMARY: Background Low-molecular-weight heparins (LMWHs) are considered members of a class of drugs with similar anticoagulant properties. However, pharmacodynamics and pharmacokinetics between LMWHs differ, which may result in different bleeding risks. As these agents are used by many patients, small differences may lead to a large effect on numbers of major bleeding events. Objectives To determine major bleeding risks for different LMWH agents and dosing schedules. Methods A cohort of acute venous thrombosis patients from four anticoagulation clinics who used an LMWH and a vitamin K antagonist were followed until they ceased LMWH treatment or until major bleeding. Exposures were classified according to different types of LMWHs and for b.i.d. and o.d. use. Cumulative incidences for major bleeding per 1000 patients and risk ratios were calculated and adjusted for study center. Results The study comprised 12 934 patients with a mean age of 59 years; 6218 (48%) were men. The cumulative incidence of major bleeding was 2.5 per 1000 patients (95% confidence interval [CI], 1.7-3.5). Enoxaparin b.i.d. or o.d. was associated with a relative bleeding risk of 1.7 (95% CI, 0.2-17.5) compared with nadroparin o.d. In addition, a nadroparin b.i.d. dosing schedule was associated with a 2.0-fold increased major bleeding risk (95% CI, 0.8-5.1) as compared with a nadroparin o.d. dosing schedule. Conclusions Absolute major bleeding rates were low for all LMWH agents and dosing schedules in a large unselected cohort. Nevertheless, twice-daily dosing with nadroparin appeared to be associated with an increased major bleeding risk as compared with once-daily dosing, as also suggested in a meta-analysis of controlled clinical trials.

Age-stratified outcome of a genotype-guided dosing algorithm for acenocoumarol and phenprocoumon.

Essentials The EU-PACT trial was used to investigate age on the interaction between coumarins and genotype. The results support the use of genotype-guided dosing for phenprocoumon in patients < 75 years. For patients ≥ 75 years the phenprocoumon algorithm should be revised and further tested. No influence of comorbidities and co-current drug use was found that could explain the differences. SUMMARY: Background Age seemed to affect the interaction between coumarins and genotype in the acenocoumarol and phenprocoumon arm of the European Pharmacogenetics of Anticoagulant Therapy (EU-PACT) trial. Objectives To investigate the effect of genotype-guided dosing stratified by age and the potential factors causing a difference. Patients/Methods Data from the acenocoumarol/phenprocoumon arm of the EU-PACT trial were used. The percentages of time below the therapeutic range, time above the therapeutic range and time in the therapeutic range (TTR) during the initial 12 weeks of therapy were compared between the genotype-guided group and the control group among younger (< 75 years) and older (≥ 75 years) patients by the use of independent t-tests, and adjusted for sex, height, weight and co-medications by the use of linear regression. Results Among younger phenprocoumon users, TTR during the first 12 weeks in the genotype-guided group (n = 55) was 9.5% (95% confidence interval [CI] 1.3 to 17.8) higher than in the control group (n = 63), with a remarkably lower percentage of time above this range (difference: - 9.6%, 95% CI - 19.0 to - 0.2) and a similar time below this range. Older patients dosed by the genotype-guided algorithm (n = 24) spent more time above the range (difference: 27.5%, 95% CI 12.9 to 42.0). For acenocoumarol users, there were no significant differences between the genotype-guided and control groups for most outcomes, except for a lower percentage of time below the range among older patients. Conclusions The genotype-guided algorithm for phenprocoumon in the EU-PACT trial benefitted younger patients more, but for older patients the algorithm needs to be revised and tested in further research.

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 hundred thirty-five phenprocoumon users (mean age 70 years, 60 % men) and 303 acenocoumarol users (mean age 69 years, 58 % men) were included. After start of statin use, the immediate phenprocoumon dosage was 0.02 mg/day (95 % CI, 0.00 to 0.03) lower. At 6 and 12 weeks, these phenprocoumon dosages were 0.03 (95 % CI, 0.01 to 0.05) and 0.07 mg/day (95 % CI, 0.04 to 0.09) lower as compared with the dosage before first statin use. In acenocoumarol users, VKA dosage was 0.04 mg/day (95%CI, 0.01 to 0.07) (immediate effect), 0.10 (95 % CI, 0.03 to 0.16) (at 6 weeks), and 0.11 mg/day (95 % CI, 0.04 to 0.18) (after 12 weeks) lower. CONCLUSIONS: Initiation of statin treatment was associated with an immediate and long-term minor although statistically significant decrease in VKA dosage in both phenprocoumon and acenocoumarol users, which suggests that statins may have anticoagulant properties.

Platelet reactivity in patients with venous thrombosis who use rosuvastatin: a randomized controlled clinical trial.

UNLABELLED: Essentials Statins, especially rosuvastatin, may reduce venous thrombosis risk, but the mechanism is unclear. We performed a randomized trial investigating the effect of rosuvastatin on platelet reactivity. Thromboxane-A2 mediated platelet aggregation was measured before and after rosuvastatin therapy. Rosuvastatin did not inhibit thromboxane-mediated platelet aggregation in venous thrombosis patients. SUMMARY: Background Statins may exert a protective effect against the risk of venous thrombosis (VT), but the mechanism is unclear. Objectives In this open-label, randomized clinical trial (www.clinicaltrials.gov NCT01613794), we aimed to determine the ex vivo effect of rosuvastatin on platelet reactivity in patients with a history of VT. Methods Platelet reactivity, in platelet reaction units (PRUs), was measured at baseline and after 28 days with VerifyNow, which uses arachidonic acid to determine thromboxane-mediated platelet aggregation, in 50 consecutive patients included in our study (25 receiving rosuvastatin and 25 without intervention). Results Forty-seven of 50 (94.0%) consecutively enrolled patients had two valid PRU measurements. The mean PRUs in rosuvastatin users were 609 at baseline and 613 at the end of the study (mean change 5; 95% confidence interval [CI] - 18 to 27). The mean PRUs in non-users were 620 at baseline and 618 at the end of the study (mean change - 2; 95% CI - 15 to 12). The mean difference in PRU change between users and non-users was 6 (95% CI - 20 to 33). After exclusion of patients who used antiplatelet medication, or had thrombocytopenia, similar results were obtained, i.e. no apparent effect of rosuvastatin on PRUs, with a mean difference in PRU change between users and non-users of - 1 (95% CI - 20 to 19). Conclusions Rosuvastatin does not affect platelet reactivity when arachidonic acid is used as an agonist in patients with a history of VT.

Increased risk of major bleeding after a minor bleed during treatment with vitamin K antagonists is determined by fixed common risk factors.

UNLABELLED: Essentials Minor bleeding is associated with subsequent major bleeding in patients treated with vitamin K antagonists. This study confirms that patients with minor bleeds have a 2.5-fold increased risk of major bleeds. A case-crossover analysis revealed that the increased risk is due to fixed underlying risk factors. Future research may unveil these unknown fixed risk factors and improve major bleeding risk scores. SUMMARY: Background Patients who have a minor bleed during treatment with vitamin K antagonists (VKAs) have a 3-fold increased risk of subsequent major bleeding. The nature of the underlying risk factors is largely unknown. Objectives To indicate why patients with minor bleeds are at increased risk of subsequent major bleeds (e.g. are risk factors of a transient or a fixed nature). Methods Patients who started VKA treatment between 2003 and 2013 were included. Exposure was from the minor bleed until 3 months later. We used two analyses: a Cox model which we adjusted for several known risk factors, and a case-crossover (CCO) design, which corrects for all fixed risk factors (such as chronic diseases and genes) as patients are compared with themselves. The combination of both analyses gives insight into whether the association of minor with major bleeds is a result of fixed or transient risk factors. Results Out of 26 130 patients who were included and followed for '61 672 patient years', 7194 experienced a minor bleed and 913 a major bleed. The Cox model indicated that patients with minor bleeds had a 2.5-fold increased risk of experiencing subsequent major bleeding after adjustment for known risk factors, whereas the CCO gave risk estimates around unity (odds ratio, 0.9; 95% confidence interval, 0.5-1.5). Conclusions The combination of both analyses indicates that minor bleeds are markers for fixed and currently unknown risk factors for major bleeding events.

Impact of point-of-care international normalized ratio monitoring on quality of treatment with vitamin K antagonists in non-self-monitoring patients: a cohort study.

BACKGROUND: Point-of-care (POC) international normalized ratio (INR) monitoring by healthcare professionals could eliminate the need for venous blood sampling in non-self-monitoring (NSM) patients on vitamin K antagonists (VKA). However, few studies have investigated the impact of POC INR monitoring on the quality of treatment in these patients and real-world data on this issue are lacking. OBJECTIVES: To investigate the safety, efficacy and quality of anticoagulant control during POC INR monitoring as compared with laboratory INR monitoring in NSM patients. METHODS: We performed a retrospective cohort study using data from the anticoagulation clinic of the Star-Medical Diagnostic Center (Rotterdam, the Netherlands). Patients who received treatment with VKA between 29 May 2012 and 29 May 2014 were eligible. Percentage of time in therapeutic range (TTR) and incidence rates of major clinical events (all-cause mortality, hospitalization, major bleeding and ischemic stroke) were compared for the year before and year after introduction of POC monitoring. Cox proportional hazard models were used to estimate hazard ratios and 95% confidence intervals for major clinical events between exposure groups. RESULTS: In total, 1973 patients during the 1-year laboratory-monitoring observation period and 1959 patients during the 1-year POC-monitoring observation period were included. Median TTR was significantly lower during POC monitoring (77.9%; 95% CI, 67.2-87.4) than during laboratory INR monitoring (81.0%; 95% CI, 71.1-90.5). Adjusted hazard ratios for major clinical events were all around unity. CONCLUSIONS: Although associated with lower TTR, POC INR monitoring is a safe and effective alternative to laboratory INR monitoring in NSM patients on VKA.

Facilitating the implementation of pharmacokinetic-guided dosing of prophylaxis in haemophilia care by discrete choice experiment.

INTRODUCTION: Patients', parents' and providers' preferences with regard to medical innovations may have a major impact on their implementation. AIM: To evaluate barriers and facilitators for individualized pharmacokinetic (PK)-guided dosing of prophylaxis in haemophilia patients, parents of young patients, and treating professionals by discrete choice experiment (DCE) questionnaire. PATIENTS/METHODS: The study population consisted of patients with haemophilia currently or previously on prophylactic treatment with factor concentrate (n = 114), parents of patients aged 12-18 years (n = 19) and haemophilia professionals (n = 91). DCE data analysis was performed, taking preference heterogeneity into account. RESULTS: Overall, patients and parents, and especially professionals were inclined to opt for PK-guided dosing of prophylaxis. In addition, if bleeding was consequently reduced, more frequent infusions were acceptable. However, daily dosing remained an important barrier for all involved. 'Reduction of costs for society' was a facilitator for implementation in all groups. CONCLUSIONS: To achieve implementation of individualized PK-guided dosing of prophylaxis in haemophilia, reduction of bleeding risk and reduction of costs for society should be actively discussed as they are motivating for implementation; daily dosing is still reported to be a barrier for all groups. The knowledge of these preferences will enlarge support for this innovation, and aid in the drafting of implementable guidelines and information brochures for patients, parents and professionals.

Optimization of vitamin K antagonist drug dose finding by replacement of the international normalized ratio by a bidirectional factor: validation of a new algorithm.

UNLABELLED: ESSENTIALS: We developed a new algorithm to optimize vitamin K antagonist dose finding. Validation was by comparing actual dosing to algorithm predictions. Predicted and actual dosing of well performing centers were highly associated. The method is promising and should be tested in a randomized trial. BACKGROUND: Oral vitamin K antagonists (VKAs) have a narrow therapeutic window and thus require frequent monitoring of its intensity by the international normalized ratio (INR). Improvement of VKA dosing defined as more time in therapeutic range (TTR) can reduce thrombotic disease and bleeding. Computerized decision support programs (CDSs) are used to optimize VKA dosing, but the effects are heterogeneous. CDSs significantly improve the proportion of time in the therapeutic INR range for initiation therapy but not the quality of anticoagulant management in an outpatient setting. One of the major problems of VKA dose finding is that the INR is a ratio and does not present linearity. We developed a new dose-finding algorithm, based on a novel bidirectional factor (BF). This BF is linear transformation of the nonlinear INR. METHODS: We compared the outcomes of the new algorithm, called BF-N, with dose finding performed at three highly ranked Dutch anticoagulation centers, using both acenocoumarol and phenprocoumon. RESULTS: The outcomes of the BF-N algorithm showed a linear correlation with VKA doses of the three centers (y = 1.001x, r(2) 0.999 for acenocoumarol and y = 0.999x, r(2) 0.999 for phenprocoumon), with a standard deviation of 3.83%. The rate of automated dosage proposals increased to 100%. CONCLUSION: The BF-N algorithm performs well in real-life settings and increases the rate of automated dosage proposals. The algorithm can be easily built into existing CDSs. Experienced staff remains necessary for complicated situations. The new algorithm needs to be evaluated in a prospective trial.

Perioperative treatment of hemophilia A patients: blood group O patients are at risk of bleeding complications.

UNLABELLED: ESSENTIALS: Targeting of factor VIII values is a challenge during perioperative replacement therapy in hemophilia. This study aims to identify the extent and predictors of factor VIII underdosing and overdosing. Blood group O predicts underdosing and is associated with perioperative bleeding. To increase quality of care and cost-effectiveness of treatment, refining of dosing is obligatory. BACKGROUND: Perioperative administration of factor VIII (FVIII) concentrate in hemophilia A may result in both underdosing and overdosing, leading to respectively a risk of bleeding complications and unnecessary costs. OBJECTIVES: This retrospective observational study aims to identify the extent and predictors of underdosing and overdosing in perioperative hemophilia A patients (FVIII levels < 0.05 IU mL(-1)). PATIENTS AND METHODS: One hundred nineteen patients undergoing 198 elective, minor, or major surgical procedures were included (median age 40 years, median body weight 75 kg). Perioperative management was evaluated by quantification of perioperative infusion of FVIII concentrate and achieved FVIII levels. Predictors of underdosing and (excessive) overdosing were analyzed by logistic regression analysis. Excessive overdosing was defined as upper target level plus ≥ 0.20 IU mL(-1). RESULTS: Depending on postoperative day, 7-45% of achieved FVIII levels were under and 33-75% were above predefined target ranges as stated by national guidelines. A potential reduction of FVIII consumption of 44% would have been attained if FVIII levels had been maintained within target ranges. Blood group O and major surgery were predictive of underdosing (odds ratio [OR] 6.3, 95% confidence interval [CI] 2.7-14.9; OR 3.3, 95% CI 1.4-7.9). Blood group O patients had more bleeding complications in comparison to patients with blood group non-O (OR 2.02, 95% CI 1.00-4.09). Patients with blood group non-O were at higher risk of overdosing (OR 1.5, 95% CI 1.1-1.9). Additionally, patients treated with bolus infusions were at higher risk of excessive overdosing (OR 1.8, 95% CI 1.3-2.4). CONCLUSION: Quality of care and cost-effectiveness can be improved by refining of dosing strategies based on individual patient characteristics such as blood group and mode of infusion.

Analytical accuracy and precision of two novel Point-of-Care systems for INR determination.

BACKGROUND: Portable point-of-care (POC) instruments for determination of the whole blood prothrombin time (PT) have been available for the last three decades. Recently, two novel POC instruments for PT and International Normalized Ratio (INR) determination in whole blood have been manufactured. The purpose of this study was to compare INR values obtained with the novel instruments (microINR® and ProTime InRhythm™) to the INR determined with the international standard for thromboplastin rTF/09. MATERIALS AND METHODS: In 60 patients treated with vitamin K-antagonists, venous whole blood was analysed with four different types of POC instruments including the novel ones. In the same patients, citrated plasma was analysed with the international standard rTF/09 and the manual tilt tube technique for clotting time determination. We assessed the bias of the INR read from the POC instruments relative to the international standard. To study the imprecision of the two novel POC instruments, duplicate INR determinations were performed. RESULTS: The results obtained with the two novel POC instruments were positively correlated with those of the international standard rTF/09. However, there was a significant bias between INR read from the novel instruments and the INR determined with rTF/09 (P < 0.001). The mean bias was -13.7% (MicroINR) and -9.3% (InRhythm). The imprecision coefficient of variation in venous blood was 5.0% and 5.1%, respectively. CONCLUSION: The imprecision of the two novel instruments is acceptable with respect to the average within-subject variation of the INR. The accuracy of the systems is borderline and should be improved by the manufacturers.

Vitamin K1 in oral solution or tablets: a crossover trial and two randomized controlled trials to compare effects.

BACKGROUND: Vitamin K1 (VK1) reverses the effects of vitamin K antagonists (VKAs). The literature shows that the bioavailability from solutions might be higher than that from tablets, possibly resulting in different effects. OBJECTIVES: To compare the bioavailability and effect on the International Normalized Ratio (INR) of 5-mg VK1 tablets and solution in three randomized clinical trials. METHODS AND RESULTS: The bioavailability was determined in a crossover trial with 25 healthy volunteers. VK1 plasma concentrations were assessed at 0, 2, 4, 5, 6, 8, 10 and 24 h, and the area under the curve was higher in the solution group than in the tablet group (mean difference 365 µg L(-1) h, 95% confidence interval [CI] 230-501, P < 0.0001). In the other two trials, the effects of both formulations on the INR were measured at 0, 24 and 48 h. In the second trial, on 72 patients on phenprocoumon with planned invasive procedures, both formulations were similarly effective, because all patients reached an INR of < 2.0, which was the primary endpoint. In the last trial, on 72 patients on phenprocoumon with an INR of 7.0-11.0, the INR decreased slightly more in the solution group (4.7, 95% CI 4.3-5.1) than in the tablet group (4.2, 95% CI 3.8-4.6). The solution group had a 3.3-fold increased likelihood (95% CI 0.7-15.1) of reaching an INR of < 2.0 at 48 h. Additionally, the increases in VK1 concentrations were similar (tablets, 3.2 µg L(-1) ; solution, 3.4 µg L(-1) ; P = 0.99) after 24 h. CONCLUSIONS: VK1 tablets are at least as clinically effective as the solution in countering VKAs.

Metformin use decreases the anticoagulant effect of phenprocoumon.

BACKGROUND: Anticoagulant therapy with vitamin K antagonists (VKAs) is affected by interaction of the VKAs with a large number of other drugs. Although metformin is generally not considered to interact with VKAs, we observed a decrease in INR after starting metformin treatment in patients using the VKA phenprocoumon. OBJECTIVES: To investigate the influence of metformin use on the dosage of phenprocoumon and INR in stably anticoagulated patients. PATIENTS: We used the database of the Anticoagulation Clinic Leiden for this study. In a population of 369 patients screened, 27 consecutive patients using phenprocoumon were prescribed metformin during the study period (1 January 2007 to 1 March 2009), without use of other concomitant medications or medical interventions that could influence the INR. RESULTS: The mean phenprocoumon dosage increased from 2.13 to 2.37 mg per day within 6 weeks (mean increase, 0.23 mg; 95% CI, 0.12-0.34) and 2.49 mg per day within 3 months (mean increase, 0.36 mg; 95% CI, 0.24-0.48) after starting metformin. The mean INR decreased from 2.88 to 2.26 (mean decrease, 0.63; 95% CI, 0.41-0.85) within 6 weeks and 2.54 (mean decrease, 0.35; 95% CI, 0.24-0.48) within 3 months after starting metformin. CONCLUSIONS: This study shows that clinicians should be aware that metformin treatment may lead to an increased optimal dosage of phenprocoumon.