New challenges and best practices for the laboratory monitoring of factor VIII and factor IX replacement.

Several recombinant factor VIII and factor IX concentrates with extended half-life (EHL) have recently been validated by clinical studies. The availability of these novel concentrates is expected to significantly facilitate the treatment of patients with hemophilia A and B. However, the modification applied to these molecules has introduced variations in their activity measurement in routine coagulation assays. Depending on the assays, underestimations of up to 10-fold or overestimations of up to approximately 30-fold in the measurements of the recovery have been reported in some factor concentrates. Such biases in monitoring may lead to major under- or overtreatment, as well as unnecessary searching for inhibitor antibodies. In this review, we discuss the guidelines and recommendations that allow the selection of optimal strategies to monitor patients treated with these novel factor concentrates. Based on the specificities of the assays and on local regulations, different chromogenic substrate assays in addition to one-stage clotting assays may be validated to allow the accurate measurement of all novel products. An efficient communication between the clinical laboratory and the clinicians is essential to ensure that the appropriate assays are carried out in laboratories and that the clinicians correctly evaluate the data. Further laboratory and clinical studies are still required for the optimization of the laboratory assays that can be used in the measurement of novel factor VIII and factor IX concentrates with EHL.

Postural control during a transition task in haemophilic children, adolescents and young adults with haemophilic ankle arthropathy.

BACKGROUND: The aim of this study was to determine whether young haemophilic boys with and without MRI-based signs of ankle arthropathy demonstrate reduced balance ability during a transition task with eyes open and eyes closed. METHODS: Thirty-four haemophilic bodies and 28 typically developing boys aged 6-20 years participated to this study. Structural integrity of the tarsal foot joints of all haemophilic boys was assessed with MRI. All participants performed a standard transition task from double-leg stance to single-leg stance with eyes open and eyes closed. Comparison of balance features derived from the centre of pressure displacement captured by a single force platform was performed between the different haemophilia subgroups and sex-age-height matched peers. FINDINGS: The haemophilic boys without signs of arthropathy presented only a higher intermediate phase velocity during the eyes closed condition (P = .05). The haemophilic boys with signs of arthropathy had significantly higher displacement after the time to new stability point, and 95% Ellipse Sway Area and Balance Area compared to their matched peers during eyes open test (P < .05). Similar findings were observed during the eyes closed test for the displacement after the time to new stability point and 95% Ellipse Sway Area (P < .05). No significant differences were observed between affected and non-affected side of the unilateral affected patients. INTERPRETATION: We suggest that the pathophysiological cascade associated with chronic bleeding episodes should not be considered as a "simple" musculoskeletal injury, hence more as a complex neurophysiological dysfunction which may originate both from unilateral and bilateral deterioration of the musculoskeletal system.

The adsorption of dabigatran is as efficient as addition of idarucizumab to neutralize the drug in routine coagulation assays.

INTRODUCTION: The direct thrombin inhibitor dabigatran interferes with thrombophilia screening and with the diagnosis of hemostasis disorders that develop during treatment with the anticoagulant. In vitro addition of idarucizumab, a humanized antibody fragment that binds dabigatran, to plasma samples containing dabigatran fully neutralizes the drug. This study was carried out to determine whether binding of dabigatran on selected insoluble commercial adsorbent material, DOAC-STOPR , was as efficient as idarucizumab to neutralize the anticoagulant activity of the drug in vitro. METHODS: Coagulation assays sensitive to dabigatran were carried out with patient and control plasma samples spiked with dabigatran and supplemented with idarucizumab or incubated with adsorbent material. RESULTS: In samples containing upto 10 000 ng/mL dabigatran, the adsorption procedure was at least as efficient as the addition of idarucizumab to neutralize the activity of the anticoagulant drug. Neither the adsorption procedure nor the addition of idarucizumab did impair routine coagulation assays carried out with plasma devoid of dabigatran, such as the activated partial thromboplastin time, prothrombin time, fibrinogen Clauss, and the thrombophilia screening assays used to detect antiphospholipid antibodies or activated protein C resistance. In addition, the adsorption procedure did not interfere with the detection of lupus anticoagulant samples. CONCLUSIONS: Adsorption of dabigatran in plasma samples containing the drug neutralizes its activity as efficiently as the addition of idarucizumab. This method allows the evaluation of thrombophilia markers without interruption of anticoagulation therapy or the detection of hemostasis disorders in patients treated with the drug.

Assessment of passive musculoarticular ankle stiffness in children, adolescents and young adults with haemophilic ankle arthropathy.

OBJECTIVES: To measure passive musculoarticular ankle stiffness (PMAAS) and its intra- and interday reliability in adult control subjects without ankle disorders. We also sought to quantify PMAAS in children, adolescents and young adults with haemophilia (CAAwH) taking into account the accurate tibiotalar and subtalar joints structural status obtained by magnetic resonance imaging (MRI). METHODS: We included 23 CAAwH and 23 typically developing boys (TDB) matched by age, weight and height, along with 25 healthy volunteers for reliability assessment. All CAAwH underwent bilateral ankle MRI, with anatomical status assessed using the International Prophylaxis Study Group MRI scale. All CAAwH underwent PMAAS testing for both sides randomly vs the dominant side (DS) in TDBs. For assessing viscous stiffness (VS) and elastic stiffness (ES), eight different oscillation frequencies were randomly repeated three times for each subject. RESULTS: Good-to-excellent intra- and interday reliability was observed for ES and VS variables. No relevant differences were observed between the ankle viscoelastic properties in CAAwH without joint damage and matched TDBs, whereas the study revealed significantly increased ES in the affected ankles of CAAwH with severe unilateral joint involvement compared to the non-affected joint. CONCLUSION: This study confirmed increased ES in the severely affected ankles of CAAwH compared to non-affected sides. No differences in the ankle viscoelastic properties of CAAwH with or without joint damage were observed, however, compared to matched TDB.

Measurement of B-domain-deleted ReFacto AF activity with a product-specific standard is affected by choice of reagent and patient-specific factors.

INTRODUCTION: Postinfusion ReFacto AF levels can be difficult to measure accurately due to discrepancies between one-stage and chromogenic FVIII assays. To overcome this, the use of the ReFacto AF laboratory standard (RAFLS) is recommended, but there are discordant reports regarding its usefulness. AIM: We investigated whether calibration with RAFLS and measurement of ReFacto AF levels are influenced by the choice of reagents and patient-specific factors in one-stage FVIII assays. METHODS: Calibration curves were generated with both the RAFLS and a plasma standard using different F8DPs and one-stage FVIII assay reagents. This selection of reagents was then used to determine FVIII levels in the plasma of patients repeatedly treated with ReFacto AF. Results were compared with those obtained with a chromogenic assay. RESULTS: F8DP devoid of von Willebrand factor (VWF) falsely increased the values of RAFLS pro-coagulant activity generated using the APTT reagent. The resulting RAFLS calibration curve underestimated ReFacto AF levels to be half of their true concentration. The use of RAFLS with F8DP containing VWF reduced the discrepancy observed between the one-stage and chromogenic FVIII assays. However, the mean difference between the two assays still varied up to 50% depending on the patient. CONCLUSIONS: The RAFLS is a suitable calibrator for one-stage FVIII assays carried out with F8DP containing VWF. However, calibration with the RAFLS does not avoid the effect of patient-specific variables that contribute to discrepancies between the measurements of ReFacto AF levels with one-stage and chromogenic FVIII assays.

Reliability and clinical features associated with the IPSG MRI tibiotalar and subtalar joint scores in children, adolescents and young adults with haemophilia.

OBJECTIVES: To assess the reliability of the IPSG MRI scale for tibiotalar (TTJ) and subtalar joint (STJ) changes in young haemophilic patients, correlating MRI findings with functional scores and 3D-rearfoot kinematics. METHODS: A total of 37 haemophilic patients underwent bilateral MRI of the footankle, clinical evaluation and quantitative assessment of their 3D-rearfoot kinematics during walking. TTJ and STJ soft tissues were assessed twice along with osteochondral changes by two radiologists using the IPSG MRI scale. Inter- and intra-observer reproducibility of MRI scoring were tested by means of kappa statistics. Correlational analyses were performed between MRI findings and the Haemophilia Joint Health Score 2.1 (HJHS) and 3D-rearfoot kinematic data. RESULTS: The intra-reader reliability of MRI scoring was good to excellent (Kappa: 0.62-1), whereas the inter-reader reliability was moderate to good (Kappa: 0.54-0.79). Weak yet significant correlations were found between the frontal plane rearfoot range of motion (ROM) during loading response of gait and STJ score, as well as between frontal plane rearfoot ROM during the terminal stance phase and the rearfoot osteochondral lesions. CONCLUSION: The IPSG score appears applicable to not only the TTJ but also the STJ. Contrary to TTJ lesions, those of the STJ do not correlate with the HJHS but do with 3D-rearfoot kinematic data.

Deficits of ankle muscle strength not found in children, adolescents and young adults with haemophilic ankle arthropathy.

OBJECTIVES: Adequate management of haemophilia patients requires early detection of joint impairment in relatively asymptomatic patients. This study sought to quantify the impact of the ankle's structural impairment on muscle strength in children, adolescent and young adults with haemophilia (CAAwH). METHODS: Twenty-three CAAwH underwent bilateral magnetic resonance imaging (MRI) assessing the anatomical status of tibiotalar joint (TTJ) and subtalar joint (STJ) using the International Prophylaxis Study Group MRI scale. An isokinetic dynamometer enabled a detailed evaluation of muscle strength at slow and fast speed. In parallel, 10 typically developing healthy boys (TDB) participated in a 1-week interval test-retest assessment to assess the test's reliability. RESULTS: Forty-six MRI ankle scores were obtained, with 11 patients unilaterally affected and one bilaterally. Of the 13 affected feet, nine showed abnormalities at TTJ, three at the posterior STJ and the remaining one at both joints. Muscle strength was not reduced in CAAwH exhibiting TTJ and/or STJ arthropathy, as compared to healthy TDB, nor was there any difference between the CAAwH's affected or unaffected sides. CONCLUSION: Contrarily to adult patients, CAAwH with repeated ankle bleeding may be less impaired than current structural evaluations imply, with possibly a latency between the occurrence of structural and functional damage.

Intensity of factor VIII treatment and the development of inhibitors in non-severe hemophilia A patients: results of the INSIGHT case-control study.

Essentials Research suggests that intensive treatment episodes may increase the risk to develop inhibitors. We performed an international nested case-control study with 298 non-severe hemophilia A patients. Surgery and a high dose of factor VIII concentrate were associated with increased inhibitor risk. Physicians need to review arguments for factor VIII dose and elective surgery extra critically. SUMMARY: Background Inhibitor development is a major complication of treatment with factor VIII concentrates in hemophilia. Findings from studies among severe hemophilia A patients suggest that intensive treatment episodes increase the risk of developing inhibitors. Objectives We set out to assess whether intensive treatment is also associated with an increased risk of inhibitor development among non-severe hemophilia A patients. Patients/Methods We performed a nested case-control study. A total of 75 inhibitor patients (cases) and 223 control patients were selected from 2709 non-severe hemophilia A patients (FVIII:C, 2-40%) of the INSIGHT cohort study. Cases and controls were matched for date of birth and cumulative number of exposure days (EDs) to FVIII concentrates. Conditional logistic regression was used to calculate both unadjusted and adjusted odds ratios (aOR); the latter were adjusted for a priori specified confounders. Results Peak treatment of 5 or 10 consecutive EDs did not increase inhibitor risk (aOR, 1.0; 95% confidence interval (CI), 0.4-2.5; and aOR, 1.8; CI, 0.6-5.5, respectively). Both surgical intervention (aOR, 4.2; CI, 1.7-10.3) and a high mean dose (> 45 IU kg-1 /ED) of FVIII concentrate (aOR, 7.5; CI, 1.6-35.6) were associated with an increased inhibitor risk. Conclusions Our findings suggest that high-dose FVIII treatment and surgery increase the risk of inhibitor development in non-severe hemophilia A. Together with the notion that non-severe hemophilia A patients are at a lifelong risk of inhibitor development, we suggest that in the future physicians will review the arguments for the FVIII dose and elective surgery extra critically.

Biomechanical markers and theoretical concepts related to haemophilic ankle and subtalar joint arthropathy: introducing the term 'haemophilic tarsal pan-arthropathy'.

BACKGROUND: Although regular factor replacement can reduce the incidence of joint bleeds and slow down the development of haemophilic arthropathy, the ankle joint remains particularly vulnerable even in children with haemophilia on primary or secondary prophylaxis and is now the primary joint affected. The heterogeneity in the pathoaetiology of haemophilic ankle arthropathy means that the functional consequences of early stage of ankle arthropathy are difficult to define as early morphological and structural changes can be observed in clinically asymptomatic ankles. In this context, understanding biomechanics of the normal and arthritic foot is complex and difficult to quantify unless considering the foot as multiple functional segments using more sophisticated assessment tools such as multisegment foot models. However, this understanding can undoubtedly aid in the analysis of an underlying clinical problem and provide a strategic basis for a more optimal management. AIMS: The purpose of this narrative review was firstly to revise information on the anatomy and biomechanics of the foot and ankle. Finally, related biomechanical markers of human motor performance, which are potentially implicated in the development of haemophilic ankle arthropathy, will be discussed based on published literature and expert opinion. MATERIALS AND METHODS: Searches in published literature were limited to the year 2000 onwards. RESULTS: Although the ankle (tibiotalar joint) is the most commonly affected joint, associated subtalar joint (SJT) involvement is often seen. This would therefore imply that an alternative phraseology might be better. DISCUSSION AND CONCLUSION: In this context, the authors propose the use of 'haemophilic tarsal pan-arthropathy' (HTPA) which encompasses both tibiotalar and subtalar joints.

The amplitude of coagulation curves from thrombin time tests allows dysfibrinogenemia caused by the common mutation FGG-Arg301 to be distinguished from hypofibrinogenemia.

INTRODUCTION: Thrombin time (TT) tests are useful for diagnosing coagulation disorders involving abnormal fibrinogen but do not allow us to distinguish between qualitative and quantitative defects. However, with the widening availability of optical coagulation automates, more information about the coagulation process is becoming increasingly accessible. METHODS: In this study, we compared the coagulation curves of TT tests carried out with plasma from healthy donors with those from patients with acquired low Clauss fibrinogen levels or with dysfibrinogenemia caused by a heterozygous point mutation in the fibrinogen γ-chain that results in a p.Arg301(275)Cys substitution. The functional fibrinogen levels of these three groups of samples were also measured with the Clauss method, and their fibrinogen protein levels were determined by ELISA. RESULTS: Our data indicate that the amplitude and maximal velocity of coagulation curves from plasma samples from FGG p.Arg301(275)Cys dysfibrinogenemic patients were comparable to those from plasma samples with fibrinogen in the normal range, whereas the amplitude of coagulation curves from patients with acquired low fibrinogen levels was lower. CONCLUSIONS: Examination of the amplitude of coagulation curves generated during TT tests may provide additional information to enable the differential diagnoses of diseases following a low fibrinogen measurement by the Clauss method.

Natural history and clinical characteristics of inhibitors in previously treated haemophilia A patients: a case series.

BACKGROUND: Development of inhibitors is the most serious complication in haemophilia A treatment. The assessment of risk for inhibitor formation in new or modified factor concentrates is traditionally performed in previously treated patients (PTPs). However, evidence on risk factors for and natural history of inhibitors has been generated mostly in previously untreated patients (PUPs). The purpose of this study was to examine cases of de novo inhibitors in PTPs reported in the scientific literature and to the EUropean HAemophilia Safety Surveillance (EUHASS) programme, and explore determinants and course of inhibitor development. METHODS: We used a case series study design and developed a case report form to collect patient level data; including detection, inhibitor course, treatment, factor VIII products used and events that may trigger inhibitor development (surgery, vaccination, immune disorders, malignancy, product switch). RESULTS: We identified 19 publications that reported 38 inhibitor cases and 45 cases from 31 EUHASS centres. Individual patient data were collected for 55/83 (66%) inhibitor cases out of 12 330 patients. The median (range) peak inhibitor titre was 4.4 (0.5-135.0), the proportion of transient inhibitors was 33% and only two cases of 12 undergoing immune tolerance induction failed this treatment. In the two months before inhibitor development, surgery was reported in nine (22%) cases, and high intensity treatment periods reported in seven (17%) cases. CONCLUSIONS: By studying the largest cohort of inhibitor development in PTPs assembled to date, we showed that inhibitor development in PTPs, is on average, a milder event than in PUPs.

Medical co-morbidities of patients with haemophilia: pain, obesity and hepatitis C.

Clinical care of patients with haemophilia (PWH) has progressed rapidly over the past decade. Current therapy has allowed patients with haemophilia to live longer and many patients are now experiencing the co-morbidities of the general population. In this review article, we focus on three common diseases states that affect PWH: chronic pain, obesity and hepatitis C. Pain has been a co-morbidity for many years and PWH often have unusual needs for chronic pain relief compared to the general population. Obesity is not only increasing in the general population but also in patients with hereditary bleeding disorders. The co-morbidity of obesity not only causes increased pain progression and joint damage but also affects the dosing of factor concentrates. Finally, hepatitis C is known to have infected the majority of patients who received non-virally inactivated pooled factor concentrates in the past. New treatment regimens have been developed that allow the nearly uniform cure of chronic hepatitis C with a short course of oral medications.

The addition of idarucizumab to plasma samples containing dabigatran allows the use of routine coagulation assays for the diagnosis of hemostasis disorders.

BACKGROUND: The anticoagulant effect of dabigatran can be approximated by its prolongation of routine coagulation assays. Consequently, dabigatran also interferes with thrombophilia screening or with diagnosing hemostasis disorders that have developed after the initiation of anticoagulant treatment, such as vitamin K deficiency or acquired hemophilia A. OBJECTIVES: This study was carried out to determine whether idarucizumab, a humanized antibody fragment that binds dabigatran, could fully neutralize dabigatran in routine diagnostic coagulation assays conducted in vitro, thereby preventing false-positive or false-negative diagnostic readouts. METHODS: Preliminary experiments identified coagulation assays that were sensitive to dabigatran, and identified a concentration of idarucizumab that neutralized the effects of dabigatran. These assays were then carried out with patient and control plasma samples spiked with dabigatran, with or without a molar excess of idarucizumab. RESULTS: Dabigatran altered the prothrombin time, activated partial thromboplastin time and thrombin time, and the measurement of intrinsic and extrinsic factor levels. Screening and confirmation tests used for lupus anticoagulant detection were prolonged by dabigatran, falsely suggesting the presence of lupus anticoagulant. Conversely, the addition of dabigatran falsely corrected an abnormal activated protein C resistance ratio. Addition of idarucizumab completely normalized these measurements, and allowed the correct identification of normal and abnormal samples with these assays. CONCLUSIONS: In vitro addition of idarucizumab to plasma samples containing dabigatran fully neutralizes the drug, and facilitates the use of routine coagulation assays to allow the diagnosis of hemostasis disorders that may be concurrently present in patients taking dabigatran.

Falling and fall risk factors in adults with haemophilia: an exploratory study.

Falls are a particular risk in persons with haemophilia (PWH) because of damaged joints, high risk of bleeding, possible impact on the musculoskeletal system and functioning and costs associated with treatment for these fall-related injuries. In addition, fall risk increases with age and PWH are increasingly entering the over 65 age group. The aim of this study was to determine the occurrence of falls during the past year and to explore which fall risk factors are present in community-dwelling PWH. Dutch speaking community-dwelling adults were included from the age of 40 years with severe or moderate haemophilia A or B, independent in their mobility and registered at the University Hospitals Leuven. They were asked to come to the haemophilia centre; otherwise a telephone survey was conducted. Demographic and social variables, medical variables, fall evaluation and clinical variables were queried. From the 89 PWH, 74 (83.1%) participated in the study. Twenty-four (32.4%) fell in the past year, and 10 of them (41.7%) more than once with an average of four falls. Living conditions, physical activity, avoidance of winter sports due to fear of falling, orthopaedic status, urinary incontinence and mobility impairments are potential fall risk factors in adult PWH. This exploratory study indicates that PWH are attentive to falling since they are at higher risk for falls and because of the serious consequences it might have. Screening and fall prevention should be stimulated in the daily practice of haemophilia care.

Pulmonary arterio-venous malformations in a patient with a novel mutation in exon 10 of the ACVRL1 gene.

Mutations of the ACVRL1 gene are a cause of hereditary haemorrhagic telangiectasia (HHT) type 2. In this case report, we present a patient with isolated pulmonary arterio-venous malformations (PAVMs) without other diagnostic criteria for HHT and a novel mutation in exon 10 of the ACVRL1 gene. Other mutations in exon 10 of ACVRL1 have been linked to the development of pulmonary artery hypertension, but PAVMs are a rare manifestation of HHT associated with ACVRL1 mutations. A disrupted endothelial TGF-beta/BMP signaling cascade underlies the pathogenesis of HHT, but the exact mechanism of the disease remains unelucidated. In particular, the factors that influence the variable clinical presentation are not fully understood.

Human liver sinusoidal endothelial cells but not hepatocytes contain factor VIII.

BACKGROUND: Although the liver is the major site of coagulation factor VIII (FVIII) synthesis, the type of cells producing FVIII within the liver is still unclear. OBJECTIVES: To measure FVIII in extracts of primary liver sinusoidal endothelial cells (LSECs) and hepatocytes, thereby preventing potential bias resulting from the modifications of the cell phenotype that can take place during in vitro culture. METHODS: LSECs were purified by flow cytometry cell sorting on the basis of their coexpression of Tie2 and CD32b. The purity of the cells was controlled by RNA sequencing. FVIII activity (FVIII:C) in extracts of purified cells was measured with a sensitive FVIII chromogenic assay, in which the specificity of the reaction is controlled by neutralization of FVIII activity with specific inhibitor antibodies. RESULTS: The FVIII:C concentration in purified LSECs ranged from 0.3 to 2.8 nU per cell. In contrast, FVIII:C was undetectable in hepatocytes. The intracellular FVIII:C concentrations are therefore at least 10-100-fold higher in LSECs than in hepatocytes. CONCLUSIONS: Our data demonstrate that LSECs, but not hepatocytes, contain measurable amounts of FVIII:C, and suggest that the former are the main cells producing FVIII in the human liver.

Obesity in haemophilia patients: effect on bleeding frequency, clotting factor concentrate usage, and haemostatic and fibrinolytic parameters.

The prevalence of obesity in patients with haemophilia (PWH) is increasing. We investigated the effect of obesity on bleeding frequency and clotting factor concentrate (CFC) usage in PWH and assessed whether prothrombotic changes observed in obesity differ between controls and PWH. Number of bleeds and CFC usage were compared between obese (N = 51) and non-obese (N = 46) haemophilia A patients. Markers of haemostasis and fibrinolysis were compared between PWH, and gender-, age- and body mass index (BMI)-matched non-haemophilic controls (N = 91). Median number of bleeds/patient-month was comparable between obese and non-obese patients with severe haemophilia (P = 0.791). Obese patients with severe haemophilia used 1.4 times more CFC/patient-month than non-obese patients (P = 0.036). When adjusting for weight this difference disappeared (P = 0.451). von Willebrand factor plasma concentration (VWF:Ag), factor VIII activity and endogenous thrombin potential were higher in obese than in non-obese controls. Obesity did not influence these markers in PWH. Plasminogen activator inhibitor type 1 levels were higher in obese vs. non-obese PWH (P < 0.001), whereas levels were comparable between PWH and controls (P = 0.912). Plasmin-α2-antiplasmin complex (PAP) levels appeared to be lower in obese vs. non-obese subjects, both within controls (P = 0.011) and PWH (P = 0.008). However, in PWH, PAP levels were higher than in controls (P < 0.001). Obesity is associated with an increase in net CFC usage in PWH, but has no effect on bleeding frequency. In addition, obesity attenuates hyperfibrinolysis in PWH. Future research investigating whether obese PWH need CFC treatment dosed on weight or whether a lower dosage would suffice to prevent and treat bleedings is needed.

Comparing normal saline versus diluted heparin to lock non-valved totally implantable venous access devices in cancer patients: a randomised, non-inferiority, open trial.

BACKGROUND: Heparin has been used for years as a locking solution in totally implantable venous access devices. Normal saline (NS) might be a safe alternative for heparin. However, evidence of non-inferiority of NS versus heparin is lacking. PATIENTS AND METHODS: We randomly allocated 802 cancer patients with a newly inserted port either to heparin lock (300 U/3 ml) or to NS lock groups in a 1:1 assignment ratio. The primary outcome was the number of functional complications, which was defined as 'easy injection, impossible aspiration' at port access. Secondary outcomes included all functional problems and catheter-related bacteraemia. We hypothesised that NS locks do not cause more functional problems and catheter-related bacteraemia than heparin locks. Non-inferiority is established if the upper limit of the confidence interval (CI) for the relative risk of NS versus heparin is <1.4. RESULTS: Three hundred and eighty-two patients from the NS group and 383 from the heparin lock group were included in the analysis. The incidence rate of our primary outcome (easy injection, impossible aspiration) was 3.70% (95% CI 2.91%-4.69%) and 3.92% (95% CI 3.09%-4.96%) of accesses in the NS and heparin groups, respectively. The relative risk was 0.94% (95% CI 0.67%-1.32%). Catheter-related bloodstream infection was 0.03 per 1000 catheter days in the NS group and 0.10 per 1000 catheter days in the heparin group. CONCLUSION: NS is a safe and effective locking solution in implantable ports if combined with a strict protocol for device insertion and maintenance.

Practical and cost-effective measurement of B-domain deleted and full-length recombinant FVIII in the routine haemostasis laboratory.

The assessment of recombinant FVIII (rFVIII) activity (FVIII:C) in plasma of patients is dependent on the assay. Notably, a calibration with a product-specific laboratory standard is recommended when measuring Refacto-AF(R) activity in plasma with a one-stage assay. The objective of this study was to facilitate the measurement of rFVIII, taking into account the recent demonstration that a calibration curve does not have to be included in each run. FVIII:C was measured in patients' samples after infusion of different types of rFVIII with a one-stage and a chromogenic assay calibrated either with pooled normal plasma or a product-specific laboratory standard. Results obtained with the one-stage coagulation assay were compared with these provided by a chromogenic assay. We confirmed that a calibration curve can be used for a prolonged period of time without loss of precision and accuracy. In such conditions, a stable relation between the calibration curves generated with a product-specific laboratory standard and plasma can be established. In patients' plasma, Refacto-AF levels measured with a one-stage FVIII assay calibrated with plasma or a product-specific laboratory standard diverged from -58% to -17% and from -25% to +18%, respectively, from the activity determined with a chromogenic substrate assay. By comparison, FVIII:C levels of full-length rFVIII measured with the one-stage assay calibrated with plasma were 6-49% lower than with the chromogenic assay. In a monocentric setting, the long-term stability of the calibration curves allows the implementation of a practical and cost-effective approach to determine rFVIII:C levels.