Activity of Von Willebrand factor and levels of VWF-cleaving protease (ADAMTS13) in preterm and full term neonates.

Von Willebrand Factor (VWF) has a central role in primary hemostasis. Its biological activity is related to the size of VWF multimers, spontaneously binding to platelets and inducing circulating microthrombi formation. This process is down-regulated by the VWF cleaving protease ADAMTS13 (A Disintegrin and Metalloprotease with ThromboSpondin motif). To date, information regarding the levels of ADAMTS13 in neonates and preterm infants is scarce. Our aim was to study ADAMTS13, VWF antigen (Ag) and Ristocetin cofactor (RiCof) activity in neonates and evaluate potential correlations with perinatal complications. Our cohort consisted of 128 (48/128: born preterm) neonates, born in Sheba Medical Center and followed until hospital discharge. Control group consisted of 20 healthy adults. As expected, a significant elevation of VWF:Ag was observed in preterm and term infants compared to adults. VWF:Ag levels were highest in full term infants (Median 129.0 IQR 33.8) and lowest in adults (Median 119.0 IQR 58.5) (p<0.05), and RiCoF levels in neonates were higher than in adults. ADAMTS13 was significantly (p<0.05) higher in preterm babies in comparison to full term and adult controls. Neonates that underwent stressful conditions or experienced vascular complications such as IUGR, ROP, NEC, had lower levels of ADAMTS13 in our study. Further studies are required to validate and asses potential significance of these findings.

N-acetyltransferase 1 polymorphism increases cotinine levels in Caucasian children exposed to secondhand smoke: the CCAAPS birth cohort.

Cotinine is a proxy for secondhand smoke (SHS) exposure. Genetic variation along nicotine and cotinine metabolic pathways may alter the internal cotinine dose, leading to misinterpretations of exposure-health outcome associations. Caucasian children with available SHS exposure and hair cotinine data were genotyped for metabolism-related genes. SHS-exposed children had 2.4-fold higher hair cotinine (0.14±0.22 ng mg(-1)) than unexposed children (0.06±0.05 ng mg(-1), P<0.001). SHS-exposed children carrying the NAT1 minor allele had twofold higher hair cotinine (0.18 ng mg(-1) for heterozygotes and 0.17 ng mg(-1) for homozygotes) compared with major allele homozygotes (0.09 ng mg(-1), P=0.0009), even after adjustment for SHS dose. These findings support that NAT1 has a role in the metabolic pathway of nicotine/cotinine and/or their metabolites. The increased cotinine levels observed for those carrying the minor allele may lead to SHS exposure misclassification in studies utilizing cotinine as a biomarker. Additional studies are required to identify functional single-nucleotide polymorphism(s) (SNP(s)) in NAT1 and elucidate the biological consequences of the mutation(s).

Oral surgery-associated postoperative bleeding in haemophilia patients - a tertiary centre's two decade experience.

Our goal in this research was to evaluate potential and targeted therapy, correlated with haemophilia severity and dental procedural risk, to reduce postoperative bleeding risk. Patients with haemophilia who were treated at the Oral and Maxillofacial Surgery Clinic at Sheba Medical Center between 1996 and 2012 comprised the study cohort. Data collected included disease history and severity, perioperative factor concentrate therapy, local haemostatic agent application, systemic tranexamic acid use and outcome. Bleeding was defined as excessive bleeding during or within 20 days following procedure. Dental procedures (n = 1968) of 125 patients were studied. Patients' bleeding risk score was evaluated according to the severity of haemophilia with or without the presence of an inhibitor, presence of comorbid coagulopathy and the type of dental procedure. Thirty-four patients undergoing a total of 880 high-risk and 1088 low-risk procedures suffered 40 postoperative bleeding events that necessitated further dental and/or haematological intervention. Among risk factors for delayed bleeding, the use of fibrin glue was significantly (P = 0.027) associated with the risk of postprocedural bleed probably as it was applied to high-risk patients and procedures. Earlier treatment period (P = 0.055), postprocedure hospitalization (P = 0.039) and dental "high-risk" procedures (P < 0.0001) also increased bleeding risk. Patients with haemophilia may be safely treated if meticulous haemostasis is applied, along with fibrin glue and systemic therapy as required. Factor transfusions are not mandatory and should be applied considering the procedure-related risk and the patient's calculated haematological risk for bleeding.

Results of a phase I/II open-label, safety and efficacy trial of coagulation factor IX (recombinant), albumin fusion protein in haemophilia B patients.

INTRODUCTION: rIX-FP is a coagulation factor IX (recombinant), albumin fusion protein with more than fivefold half-life prolongation over other standard factor IX (FIX) products available on the market. AIM: This prospective phase II, open-label study evaluated the safety and efficacy of rIX-FP for the prevention of bleeding episodes during weekly prophylaxis and assessed the haemostatic efficacy for on-demand treatment of bleeding episodes in previously treated patients with haemophilia B. METHODS: The study consisted of a 10-14 day evaluation of rIX-FP pharmacokinetics (PK), and an 11 month safety and efficacy evaluation period with subjects receiving weekly prophylaxis treatment. Safety was evaluated by the occurrence of related adverse events, and immunogenic events, including development of inhibitors. Efficacy was evaluated by annualized spontaneous bleeding rate (AsBR), and the number of injections to achieve haemostasis. RESULTS: Seventeen subjects participated in the study, 13 received weekly prophylaxis and 4 received episodic treatment only. No inhibitors were detected in any subject. The mean and median AsBR were 1.25, and 1.13 respectively in the weekly prophylaxis arm. All bleeding episodes were treated with 1 or 2 injections of rIX-FP. Three prophylaxis subjects who were treated on demand prior to study entry had >85% reduction in AsBR compared to the bleeding rate prior to study entry. CONCLUSION: This study demonstrated the efficacy for weekly routine prophylaxis of rIX-FP to prevent spontaneous bleeding episodes and for the treatment of bleeding episodes. In addition no safety issues were detected during the study and an improved PK profile was demonstrated.

Combined administration of FVIII and rFVIIa improves haemostasis in haemophilia A patients with high-responding inhibitors--a thrombin generation-guided pilot study.

Treatment of haemophilia A patients with inhibitors is challenging, and may require individually tailored regimens. Whereas low titre inhibitor patients may respond to high doses of factor VIII (FVIII), high-responding inhibitor patients render replacement therapy ineffective and often require application of bypassing agents. Thrombin generation (TG) assays may be used to monitor haemostasis and/or predict patients' response to bypass agents. In this study we defined by TG, the potential contribution of FVIII to recombinant activated factor VII (rFVIIa)-induced haemostasis in inhibitor plasma. Based upon results, prospectively designed individual regimens of coadministration of rFVIIa and FVIII were applied. Plasma samples from 14 haemophilia patients with inhibitors (including high titre inhibitors) were tested. The response to increasing concentrations of FVIII, rFVIIa or both was assayed by TG. Eight patients, chosen following consent and at physician's discretion, comprised the combined FVIII-rFVIIa therapy clinical study cohort. Combined spiking with FVIII/rFVIIa improved TG induced by rFVIIa alone in all inhibitor plasmas. Combined rFVIIa and FVIII therapy was applied during bleeding or immune tolerance to eight patients, for a total of 393 episodes. Following a single combined dose, 90% haemostasis was documented and neither thrombosis nor any complications evolved. During study period decline of inhibitor levels and bleeding frequency were noted. Pre-analytical studies enabled us to prospectively tailor individual therapy regimens. We confirmed for the first time that the in vitro advantage of combining FVIII and rFVIIa, indeed accounts for improved haemostasis and may safely be applied to inhibitor patients.

Adverse placental effect of formic acid on hCG secretion is mitigated by folic acid.

AIMS: Formic acid has recently been detected in maternal blood and umbilical cord blood of infants born to alcohol abusing mothers. This toxic metabolite of methanol requires folate for detoxification. We hypothesized that formic acid produced in the maternal circulation will transfer across the placenta and will be toxic to the placenta. Our objectives were, first, to determine whether formic acid transfers across the human placenta and whether it is toxic to the placenta and second, to determine whether folate can decrease transplacental transfer of formic acid and mitigate toxicity. METHODS: Dual perfusion of a single placental lobule ex vivo was used to characterize the transfer of formic acid across the placenta. After a 1-h control period, formic acid (2 mM) was introduced into the maternal circulation with (n = 4) or without folate (1 µM) (n = 4) and was allowed to equilibrate for 3 h. RESULTS: Formic acid transferred rapidly from the maternal to the fetal circulation, and transfer was not altered with the addition of folate. Compared with the control period, there was a significant decrease in hCG secretion (P = 0.03) after addition of formic acid. The addition of folic acid to the perfusate mitigated the decrease in hCG. CONCLUSIONS: Formic acid rapidly transfers across the placenta and thus has the potential to be toxic to the developing fetus. Formic acid decreases hCG secretion in the placenta, which may alter steroidogenesis and differentiation of the cytotrophoblasts, and this adverse effect can be mitigated by folate.

Recombinant factor concentrates may increase inhibitor development: a single centre cohort study.

Recent reports have raised concerns regarding potential risk factors for inhibitor development. In Israel, all haemophilia patients (n = 479) are followed by the National Hemophilia Center. Most children are neonatally exposed to factor concentrate (due to circumcision performed at the age of 8 days). The impact of early exposure and recombinant FVIII products (rFVIII) administration (approved in Israel since 1996) upon inhibitor occurrence in our cohort of haemophilia A (HA) patients was analysed. Two hundred ninety-two consecutive paediatric cases with a first symptomatic onset of HA were enrolled and followed over a median time of 7 years [min-max: 9 months to 17 years]. Study endpoint was inhibitor development against factor VIII. In addition, the treatment regimens applied, i.e. bolus administration or 'continuous infusion' and the family history of inhibitor development were investigated. During the follow-up period 31/292 children (10.6%) developed high titre inhibitors. Inhibitors occurred in 14/43 (32.5%) HA patients neonatally exposed to rFVIII, as compared to 22/249 previously treated with Plasma Derived (PD) products (8.8%). The odds ratio for inhibitor formation in rFVIII treated HA patients was 3.43 (95% CI: 1.36-8.65). Transient inhibitor evolved among 2/43 paediatric HA patients, only among those treated with rFVIII. The risk of inhibitor detection significantly increased among HA children treated by continuous infusion (P = 0.025). Our experience shows that the risk of inhibitor formation may be increased by early exposure to recombinant concentrates. The multiple variables affecting inhibitor incidence deserve further attention by larger prospective studies.

Lower doses of rFVIIa therapy are safe and effective for surgical interventions in patients with severe FXI deficiency and inhibitors.

Severe FXI deficiency is a rare injury-related bleeding disorder. In patients with FXI inhibitors, surgeries may be treated using recombinant activated factor VII; however, treatment safety is a major concern and the best dosing regimen as well as mode of administration is still to be defined. We describe four patients with severe factor XI deficiency and inhibitors to FXI, undergoing eight (four major) surgical procedures treated with continuous infusion of rFVIIa. Following acute MI that evolved after surgery of our first patient, all other patients were treated with low-dose bolus rFVIIa followed by low-dose continuous infusion of rFVIIa. Haemostasis was successfully achieved and no further thrombotic complications occurred. To support our clinical results ex-vivo thromboelastography studies were performed, demonstrating the differences of clot formation and lysis between patients with FXI deficiency and healthy controls and suggesting that low-dose rFVIIa corrects coagulation similarly to high-dose rFVIIa in FXI deficiency. Recombinant FVIIa at low doses may effectively induce haemostasis and seems to be a safe treatment mode in patients with FXI deficiency and inhibitors undergoing surgeries.

Stability, efficacy, and safety of continuously infused sucrose-formulated recombinant factor VIII (rFVIII-FS) during surgery in patients with severe haemophilia.

Bolus injection (BI) of sucrose-formulated recombinant factor VIII (rFVIII-FS) is an approved treatment for haemophilia patients undergoing major surgery. Continuous infusion (CI) during surgery has potential benefits by providing steady administration of replacement factor to the patient, avoiding high peaks and low troughs. We tested the stability of rFVIII-FS under CI conditions and conducted a single-centre, open-label, phase III study to evaluate the efficacy and safety of CI using rFVIII-FS in haemophilia A patients undergoing surgery. Patients received bolus rFVIII-FS to achieve >or=80% FVIII levels 30-60 min presurgery, followed by CI of rFVIII-FS at a rate calculated to maintain haemostatic factor levels until days 8-10 post surgery. The rate of infusion was adjusted according to daily calculations derived from the actual clearance. The stability of rFVIII-FS was found to be appropriate for CI for 7 days under the same conditions as clinical settings. Fourteen patients (mean age 37.8 years) receiving on-demand FVIII treatment without a history of inhibitors underwent 15 surgical procedures including joint replacements, synovectomies, multiple tooth extractions, and cholecystectomy. Bleeding was similar to that observed in non-haemophilia patients undergoing similar operations in the same department. Haemostasis during surgery was considered by the attending surgeons as 'excellent' or 'good' in all cases; study investigators rated all 15 cases as 'excellent' overall. There were no adverse events, including inhibitor formation, related to rFVIII-FS. rFVIII-FS was found to be suitable for use in CI in haemophilia A patients undergoing major surgery.

The role of placental breast cancer resistance protein in the efflux of glyburide across the human placenta.

Gestational diabetes mellitus is a common medical complication in pregnancy. Recent findings demonstrate that glyburide is effluxed against a concentration gradient from the fetal to the maternal circulation. However, the transport systems involved in the active efflux of glyburide in the human placenta have not yet been identified. The ATP-binding cassette transporter, breast cancer resistance protein (BCRP), is highly expressed in placental syncytiotrophoblast suggesting it may play a role in protecting the fetus from drug toxicity. The objective of the present study was to determine whether BCRP participates in the transport of glyburide across the human placenta. The placental transfer of glyburide in the presence of specific BCRP inhibitor, nicardipine, was investigated using the ex vivo dual perfusion system of isolated human placental lobules. In a closed experiment, glyburide was added (200 ng/mL) to the maternal and fetal circulations and the BCRP inhibitor (20 microM) was added to the maternal circulation. Samples were taken during pre-control, experimental, and post-control periods for measurement of glyburide and markers of tissue viability. Results obtained from perfusions (n=4) in the presence of the BCRP inhibitor show a significant increase in the mean fetal-to-maternal concentration ratio of glyburide determined at 180 min, 0.56+/-0.06, when compared to the mean ratio obtained in the absence of inhibitor, 0.32+/-0.06 (p=0.04). These data indicate that nicardipine partially blocked the transfer of glyburide across the whole placenta through its inhibition of BCRP. This is the first ex vivo evidence that BCRP actively transports glyburide.

Aspirin responsiveness in acute brain ischaemia: association with stroke severity and clinical outcome.

PURPOSE: Platelets play a critical role in the pathogenesis of acute brain ischaemia. We studied the association between the degree of inhibition of platelet function by aspirin (ASA) and the severity and outcome of acute brain ischaemia. METHODS: Platelet responsiveness to ASA was assessed in patients with acute brain ischaemia, treated with ASA since hospital admission. The degree of ASA responsiveness was assessed by optical aggregometry and categorized into patients with good response, partial response and complete unresponsiveness to ASA (good responders, partial responders and non-responders, respectively). An additional evaluation of responsiveness to ASA was performed by Impact-R (cone and platelet analyzer). Patients underwent serial clinical assessment during hospitalization, at discharge and during follow-up. RESULTS: Among 105 patients (mean age 63 +/- 12 years; 66% men), impaired ASA responsiveness at baseline as assessed by aggregometry was associated with increased stroke severity at baseline, unfavourable clinical course, and poor functional outcome during follow-up (p < 0.05 for all). Age-adjusted odds ratios in non-responders compared to good responders were 9.8 for severe stroke on admission (95% CI 2.8-34.9), 3.1 for lack of early clinical improvement (95% CI 1.1-8.8) and 8.6 for poor functional outcome during follow-up (95% CI 2.4-30.4). Less robust trends were observed with the Impact-R. CONCLUSIONS: Impaired responsiveness to ASA in acute brain ischaemia is common and is associated with worse neurological deficits at stroke onset, early clinical deterioration and poorer functional outcome. The clinical significance of these findings requires further evaluation in larger longitudinal studies.

Investigating the potential role of multi-drug resistance protein (MRP) transporters in fetal to maternal glyburide efflux in the human placenta.

Glyburide, a drug used to treat gestational diabetes has previously been shown not to be measurable in fetal blood, and to be transferred from the fetal to the maternal circulation against a concentration gradient. The objective of the study is to determine whether indomethacin, an inhibitor of the multi-drug resistance family (MRP) of transporters is involved in the active efflux of glyburide from the fetus to the mother. Using the dually perfused human placental cotyledon model, 12 perfusions were performed of both glyburide and indomethacin concomitantly. The rate of transfer of glyburide in the presence of inhibitor was not different from the rate of transfer of glyburide in the absence of inhibitor. Furthermore, our study suggests that MRP1, 2 or 3 may be only minimally involved in the transport of glyburide across the human placenta. These results pose other ABC transporters, such as likely candidates for the placental transfer of glyburide.

Acquired prolactin deficiency in patients with disorders of the hypothalamic-pituitary axis.

UNLABELLED: Acquired PRL deficiency occurs when the anterior pituitary is functionally destroyed, and it usually accompanies other pituitary hormone deficiencies. We retrospectively investigated in an outpatient endocrine clinic of a major tertiary medical center the prevalence and clinical characteristics of acquired PRL deficiency in patients with diseases of the hypothalamic-pituitary axis. The study included 100 consecutive patients, 61 men and 39 women, aged 4-79 yr at diagnosis. Patients were divided by PRL level to normal (>5 ng/ml), mild (3-5 ng/ml), and severe deficiency (<3 ng/ml). Twenty-seven patients (27%) had PRL deficiency, 13 mild deficiency and 14 severe deficiency. Patients with severe PRL deficiency tend to be younger at diagnosis (mean age, 37.5+/-21.8 yr) than patients with normal PRL (46+/-18.5 yr; ns). Underlying diseases including pituitary apoplexy, non-functioning pituitary adenoma, craniopharyngioma, and idiopathic hypogonadotropic hypogonadism were associated with PRL deficiency. The incidence of severe PRL deficiency rose with an increase in the number of other pituitary hormone deficits (ACTH, TSH, gonadotropin, vasopressin), from 0 in patients with no other deficits to 38% in patients with 4 deficits (p=0.006). Patients with severe deficiency had a mean of 3 hormone deficits compared to 1.8 in the other groups (p=0.006). PRL deficiency was significantly associated with TSH, ACTH and GH deficiency. CONCLUSIONS: PRL deficiency is common in patients with hypothalamic-pituitary disorders, especially pituitary apoplexy and craniopharyngioma. Acquired severe PRL deficiency can be considered a marker for extensive pituitary damage and a more severe degree of hypopituitarism.

Examining the transplacental passage of apixaban using the dually perfused human placenta.

UNLABELLED: Essentials Apixaban is a novel oral anticoagulant that has not been studied in pregnant patients. Our objective was to determine the rate and extent of the placental transfer of apixaban. Apixaban rapidly crosses the ex vivo term human placenta from maternal to fetal circulation. Fetal apixaban levels in vivo are estimated to be 35-90% of the corresponding maternal levels. SUMMARY: Background Apixaban is a novel oral anticoagulant that is increasingly being prescribed to women of reproductive age. However, information regarding its placental transfer is non-existent. Objective To determine the rate and extent of placental transfer of apixaban, using the human placenta ex vivo. Methods Placentae collected after Caesarean or vaginal delivery of healthy term infants were perfused in the respective maternal and fetal circulation. At the start of the experiment, apixaban was added to the maternal circulation at a concentration of 150 ng mL(-1) , and samples from maternal and fetal reservoirs were collected over 3 h. Results There was a rapid decline of apixaban in the maternal compartment, followed by emergence in the fetal compartment with a median fetal-to-maternal drug concentration ratio of 0.77 (interquartile range [IQR], 0.76-0.81) and fetal concentration of 39.0 ng mL(-1) (IQR, 36.8-40.6) after 3 h (n = 5). The perfusion results were subsequently adjusted to account for differences in the concentration of plasma proteins in maternal and fetal blood, as apixaban remains highly bound to albumin and alpha-1 acid glycoprotein. After the adjustment, the predicted fetal-to-maternal ratio of total (bound plus unbound) apixaban concentrations in vivo ranged from 0.35 to 0.90. Conclusions We conclude that unbound apixaban rapidly crosses from the maternal to fetal circulation. We further predict that total apixaban concentrations in cord blood in vivo are 35-90% of the corresponding maternal levels, suggesting that apixaban could have a possible adverse effect on fetal and neonatal coagulation.

The effect of the plasma levels of proteins C and S on the prediction of warfarin maintenance dose requirements.

OBJECTIVE: Determination of the effects of the vitamin K-dependent anticoagulants, proteins C and S, on warfarin dose requirements and on the prediction error of a bayesian warfarin dose predicting program. METHODS: Patients in the study were consecutive inpatients (n = 18) starting treatment with warfarin who were monitored as outpatients for 4 weeks. The following measurements were taken: repeated (n = 8) prothrombin times, expressed as the international normalized ratio (INR), plasma protein C and S antigen levels (percentage of pooled normal plasma), demographic, clinical and biochemical variables. RESULTS: Maintenance doses (adjusted to INR 2.5) were 6.7 +/- 3.4 mg/day. Protein C decreased to 56.9% +/- 15.3%, protein S to 63.7% +/- 17.3%, INR increased to 2.46 +/- 0.14. Prediction error decreased from 2.84 +/- 2.0 mg/day to 0.95 +/- 0.78 mg/day. Protein C accounted for only 4.2% of the mean maintenance dose but protein C and S levels accounted for 31% of the mean dose prediction error. CONCLUSION: Protein C and S levels affect warfarin doses and predictions significantly but not to a clinically meaningful degree.

Interindividual variability in sensitivity to warfarin--Nature or nurture?

BACKGROUND: Interindividual variability in responses to warfarin is attributed to dietary vitamin K, drug interactions, age, or genetic polymorphism in the cytochrome P4502C9 enzyme (CYP2C9) (allelic variants 2C9*2 and 2C9*3 ) linked with impaired metabolism of the potent enantiomere S-warfarin. PATIENTS AND METHODS: We quantified the relative effects of age and of simultaneously determined CYP2C9 genotype, plasma warfarin and vitamin K concentrations, and concurrent medications on warfarin maintenance doses in 156 patients at optimized stable anticoagulation. RESULTS: Allele frequencies for CYP2C9*1, CYP2C9*2, and CYP2C9*3 were 0.84, 0.10, and 0.06. Warfarin doses were 6.5 +/- 3.2, 5.2 +/- 2.4, and 3.3 +/- 2.0 mg/d in the 3 genotype groups (P < .0001). Warfarin doses decreased with age as follows: 7.7 +/- 3.7 versus 4.9 +/- 2.9 mg/d at < 50 years and >66 years (P < .001), mainly as a result of decreased plasma warfarin clearance (2.8 +/- 1.4 mL/min versus 1.9 +/- 0.8 mL/min; P < .001). Vitamin K (1.6 +/- 1.1 ng/mL) did not differ among the age or genotype groups. Patients >or=66 years old with the CYP2C9*3 allele required only 2.2 +/- 1.2 mg/d compared with 7.9 +/- 3.7 mg/d in those

A new approach to treatment of bleeding episodes in young hemophilia patients: a single bolus megadose of recombinant activated factor VII (NovoSeven).

Recombinant activated factor VII (rFVIIa, NovoSeven) represents an effective treatment for hemophilia patients with inhibitors, but no consensus as to the best dosing regimen exists. We assessed the efficacy and safety of a rFVIIa 'megadose' (300 micro g kg(-1) bolus) as treatment for bleeds in three young inhibitor patients. Of 114 bleeds, 95 responded to a single dose. Pain relief was faster and therapy duration significantly shorter than with continuous infusion (CI) regimens or standard boluses (90 micro g kg(-1) every 3 h). Rebleeding occurred in 9.6% of cases and 19/114 episodes required a second bolus injection. Although rFVIIa consumption per bleed (median: 300 micro g kg(-1)) was higher than with standard boluses (180-270 micro g kg(-1)), patients found single bolus administration more convenient than recurrent injections or CI. With two exceptions, no complications occurred within 3 h of treatment, despite high FVII:C levels (median: 27.4 U mL(-1); range: 19.8-54 U mL(-1)). Treatment of bleeds with a rFVIIa megadose in young inhibitor patients is effective and well tolerated.

Vitamin K intake and sensitivity to warfarin in patients consuming regular diets.

The effect of dietary vitamin K intake on warfarin sensitivity is known only from case reports and few small clinical studies. We followed 50 patients commencing warfarin and consuming their regular diets (for 8 weeks) to study this relationship. A one-week recall dietary questionnaire was completed at weeks 2 and 8. Daily intake of nutrients and vitamin K was calculated from standard tables. Warfarin sensitivity index (WSI) was defined as final INR/final warfarin dose (mg/day/m2 of body surface area) (week 8). Vitamin K intake was 17-974 (median: 179) microg/day. Median WSI was 0.82 (0.31-4.47). A WSI value of 1.1 significantly separated excess (>250 microg/day) from normal (<250 microg/day) vitamin K consumers (16/18 vs. 15/32, respectively, p <0.01). The former had lower day 5 INR (median: 1.9 vs. 3.0, p <0.001), needed more warfarin to achieve INR > or =2.0 (32.0+/-9.2 mg vs. 25.4+/-6.4 mg, p = 0.009) and required a higher maintenance steady state warfarin dose (5.7+/-1.7 mg/day vs. 3.5+/-1.0 mg/day, p <0.001). We conclude that in 32% (16/50) of anticoagulated patients under usual dietary conditions sensitivity to warfarin is decreased by vitamin K intake > or =250 microg/day.

Pharmacokinetic studies with FVIII/von Willebrand factor concentrate can be a diagnostic tool to distinguish between subgroups of patients with acquired von Willebrand syndrome.

Acquired von Willebrand syndrome (AVWS) has been associated mainly with monoclonal gammopathy of uncertain significance (MGUS), clonal lymphoproliferative or myeloproliferative disorders and autoimmunity. In the present work we studied 6 patients with AVWS: four with MGUS IgG (lambda or kappa), one with small lymphocytic lymphoma and one with agnogenic myeloid metaplasia (AMM). All the patients underwent a pharmacokinetic analysis at presentation in order to study potential differences in recovery, clearance (CL) or terminal half-life (THL) following administration of von Willebrand factor (VWF) concentrate. In all the patients with AVWS an increase in clearance and a decrease in THL was observed as compared to these parameters in patients with hereditary type 3 von Willebrand disease (VWD). No difference in recovery was observed among the groups. The increase in clearance and the decrease in THL were significantly more pronounced in the group of MGUS patients (57.93 +/- 25.6 ml/h/kg, and 1.39 +/- 0.5 h, respectively) as compared to these parameters in the AMM (8.06 ml/h/kg, and 6.96 h, respectively) or the lymphoma (4.76 ml/h/kg, and 6.76 h. respectively) patients (p = 0.03 for clearance and 0.001 for THL). These data indicate that the pharmacokinetic analysis can be a useful tool to distinguish between MGUS-related and other causes of AVWS, and to plan an appropriate treatment accordingly.