Impact of trauma centre capacity and volume on the mortality risk of incoming new admissions.

INTRODUCTION: Trauma centre capacity and surge volume may affect decisions on where to transport a critically injured patient and whether to bypass the closest facility. Our hypothesis was that overcrowding and high patient acuity would contribute to increase the mortality risk for incoming admissions. METHODS: For a 6-year period, we merged and cross-correlated our institutional trauma registry with a database on Trauma Resuscitation Unit (TRU) patient admissions, movement and discharges, with average capacity of 12 trauma bays. The outcomes of overall hospital and 24 hours mortality for new trauma admissions (NEW) were assessed by multivariate logistic regression. RESULTS: There were 42 003 (mean=7000/year) admissions having complete data sets, with 36 354 (87%) patients who were primary trauma admissions, age ≥18 and survival ≥15 min. In the logistic regression model for the entire cohort, NEW admission hospital mortality was only associated with NEW admission age and prehospital Glasgow Coma Scale (GCS) and Shock Index (SI) (all p<0.05). When TRU occupancy reached ≥16 patients, the factors associated with increased NEW admission hospital mortality were existing patients (TRU >1 hour) with SI ≥0.9, recent admissions (TRU ≤1 hour) with age ≥65, NEW admission age and prehospital GCS and SI (all p<0.05). CONCLUSION: The mortality of incoming patients is not impacted by routine trauma centre overcapacity. In conditions of severe overcrowding, the number of admitted patients with shock physiology and a recent surge of elderly/debilitated patients may influence the mortality risk of a new trauma admission.

Mathematical model of thrombin generation and bleeding phenotype in Amish carriers of Factor IX:C deficiency vs. controls.

INTRODUCTION: Factor IX:C (FIX:C) levels vary in hemophilia B carriers even in pedigrees with a unifying genetic defect. Analyzing the balance between pro-and anticoagulants might increase our understanding of carriers' bleeding potential. AIM: In this research study, we evaluated bleeding scores (BS) and a novel mathematical model of thrombin generation (TG) in Amish FIX:C deficient carriers and controls. METHODS: Blood samples and BS were obtained from post-menarchal females, including 59 carriers and 57 controls from the same extended pedigree. Factors II, V, VII, VIII, IX, X, antithrombin, tissue factor pathway inhibitor and protein C were assayed to generate mathematical models of TG in response to 5pM tissue factor (TF) and for TF + thrombomodulin. BS was based on a modification of the MCMDM-1VWD scoring system. RESULTS: Carriers had a lower mean FIX:C (68% vs. 119%), von Willebrand factor antigen (108 vs.133) and Tissue activatable fibrinolysis inhibitor (103 vs. 111) compared to controls; both groups had a similar mean BS. Carriers demonstrated significantly lower TG parameters on both mathematical models compared to controls. Carriers with FIX:C ≤ 50% had lower TG curves than those >50% but similar BS. CONCLUSION: Thrombin generation showed significant differences between carriers and controls, between low (≤50%) and high (>50%) FIX:C carriers, and specifically in the TF + thrombomodulin model, between high FIX:C carriers and controls, although the BS were not different.

Distinguishing lupus anticoagulants from factor VIII inhibitors in haemophilic and non-haemophilic patients.

INTRODUCTION: Accurate diagnosis of an inhibitor, a neutralizing antibody to infused factor VIII (FVIII), is essential for appropriate management of haemophilia A (HA). Low-titre inhibitors may be difficult to diagnose due to high rates of false-positive inhibitor results in that range. Transient low-titre inhibitors and false-positive inhibitors may be due to the presence of a lupus anticoagulant (LA) or other non-specific antibodies. Fluorescence immunoassay (FLI) to detect antibodies to FVIII is a sensitive method to identify inhibitors in HA. Evaluations of antibody profiles by various groups have demonstrated that haemophilic inhibitors detected by Nijmegen-Bethesda (NBA) and chromogenic Bethesda (CBA) assays correlate with positivity for anti-FVIII immunoglobulin (Ig) G1 and G4. AIM: This study sought to determine whether FLI could distinguish false-positive FVIII inhibitor results related to LAs from clinically relevant FVIII inhibitors in HA patients. METHODS: Samples from haemophilic and non-haemophilic subjects were tested for LA, specific FVIII inhibitors by NBA and CBA, and anti-FVIII immunoglobulin profiles by FLI. RESULTS: No samples from LA-positive non-haemophilic subjects were positive by FLI for anti-FVIII IgG4. Conversely, 91% of NBA-positive samples from haemophilia subjects were positive for anti-FVIII IgG4. Two of 11 haemophilia subjects had samples negative for anti-FVIII IgG4 and CBA, which likely represented LA rather than FVIII inhibitor presence. CONCLUSIONS: Assessment of anti-FVIII profiles along with the CBA may be useful to distinguish a clinically relevant low-titre FVIII inhibitor from a transient LA in HA patients.

Laboratory testing for factor VIII and IX inhibitors in haemophilia: A review.

Inhibitors are antibodies directed against haemophilia treatment products which interfere with their function. Factor VIII (FVIII) inhibitors in haemophilia A and factor IX (FIX) inhibitors in haemophilia B are significant clinically when they require a change in a patient's treatment regimen. Their persistence may increase morbidity and mortality. Multiple laboratory tests are now available for detecting and understanding inhibitors in haemophilia. Inhibitors are traditionally measured by their interference in clotting or chromogenic factor assays. They may also be detected using immunologic assays, such as enzyme-linked immunosorbent assay or fluorescence immunoassay. Anti-FVIII or anti-FIX antibodies of IgG4 subclass best correlate with the presence of functional inhibitors. Improvements in inhibitor measurement have been recently introduced. Preanalytical heat treatment of patient specimens allows testing of patients without delaying treatment. Use of chromogenic and immunologic assays may aid in identification of false-positive results, which are frequent among low-titre inhibitors. Validated reagent substitutions can be used to reduce assay cost. New methods for defining assay positivity and reporting low-titre inhibitors have been suggested. Challenges remain in the areas of quality control, assay standardization, monitoring of patients undergoing immune tolerance induction therapy and testing in the presence of modified and novel treatment products.

Effects of pre-analytical heat treatment in factor VIII (FVIII) inhibitor assays on FVIII antibody levels.

INTRODUCTION: The use of pre-analytical heat treatment (PHT) with the Nijmegen-Bethesda assay (NBA) for inhibitors to factor VIII (FVIII) can remove/destroy infused or endogenous FVIII from patient plasma samples, allowing testing of recently infused patients with haemophilia. Two PHT methods have been described as follows: heating to 56°C for 30 minutes and heating to 58°C for 90 minutes. Data examining the effects of PHT on anti-FVIII IgG4 , the antibodies known to correlate most closely with the presence of FVIII inhibitors, are limited. AIM: To assess the effect of PHT on the levels of detectable anti-FVIII IgG4 . METHODS: Nijmegen-Bethesda assay-positive specimens were incubated at 56, 58 or 60°C for 90 minutes, and anti-FVIII IgG4 was measured by fluorescence immunoassay (FLI) at 30-minute intervals. The effects of PHT on the ability of recombinant FVIII (rFVIII) to inhibit detection of patient antibodies by FLI was also examined to assess the stability of rFVIII under the various PHT conditions tested. RESULTS: Levels of anti-FVIII IgG4 showed little change following incubations at 56°C (mean 101% of original value at 30 minutes and 100% at 60 minutes) but decreased upon exposure to 58°C (mean 85% at 30 minutes and 66% at 60 minutes). In addition, heating to 56°C effectively decreased the ability of rFVIII to block antibody binding compared to unheated rFVIII. CONCLUSION: The optimal temperature for PHT in the FVIII NBA is 56°C. Higher temperatures may lead to loss of inhibitory antibodies.

Limit of detection and threshold for positivity of the Centers for Disease Control and Prevention assay for factor VIII inhibitors.

Essentials Immunologic methods detect factor VIII (FVIII) antibodies in some inhibitor-negative specimens. Specimens were tested by modified Nijmegen-Bethesda assay (NBA) and fluorescence immunoassay. The NBA with preanalytical heat inactivation detects FVIII inhibitors down to 0.2 NBU. IgG4 frequency validates the established threshold for positivity of ≥ 0.5 NBU for this NBA. SUMMARY: Background The Bethesda assay for measurement of factor VIII inhibitors called for quantification of positive inhibitors by using dilutions producing 25-75% residual activity (RA), corresponding to 0.4-2.0 Bethesda units, with the use of 'more sensitive methods' for samples with RA closer to 100% being recommended. The Nijmegen modification (Nijmegen-Bethesda assay [NBA]) changed the reagents used but not these calculations. Some specimens negative by the NBA have been shown to have FVIII antibodies detectable with sensitive immunologic methods. Objective To examine the performance at very low inhibitor titers of the Centers for Disease Control and Prevention (CDC)-modified NBA (CDC-NBA), which includes preanalytic heat inactivation to liberate bound anti-FVIII antibodies. Methods Specimens with known inhibitors were tested with the CDC-NBA. IgG4 anti-FVIII antibodies were measured by fluorescence immunoassay (FLI). Results Diluted inhibitors showed linearity below 0.4 Nijmegen-Bethesda units (NBU). With four statistical methods, the limit of detection of the CDC-NBA was determined to be 0.2 NBU. IgG4 anti-FVIII antibodies, which correlate most strongly with functional inhibitors, were present at rates above the background rate of healthy controls in specimens with titers ≥ 0.2 NBU and showed an increase in frequency from 14.3% at 0.4 NBU to 67% at the established threshold for positivity of 0.5 NBU. Conclusions The CDC-NBA can detect inhibitors down to 0.2 NBU. The FLI, which is more sensitive, demonstrates anti-FVIII IgG4 in some patients with negative (< 0.5) NBU. The sharp increase in IgG4 frequency between 0.4 and 0.5 NBU validates the established threshold for positivity of ≥ 0.5 NBU for the CDC-NBA, supporting the need for method-specific thresholds.

Survey of the anti-factor IX immunoglobulin profiles in patients with hemophilia B using a fluorescence-based immunoassay.

Essentials Studies characterizing neutralizing antibodies (inhibitors) in hemophilia B (HB) are lacking. The current study describes anti-factor (F) IX antibody profiles in 37 patients who have HB. Anti-FIX IgG4 levels exhibited a strong positive correlation with Nijmegen-Bethesda results. These data will help to more clearly define, predict, and treat alloantibody formation in HB. SUMMARY: Background Hemophilia B (HB) is an inherited bleeding disorder caused by the absence or dysfunction of coagulation factor IX (FIX). A subset of patients who have HB develop neutralizing alloantibodies (inhibitors) against FIX after infusion therapy. HB prevalence and the proportion of patients who develop inhibitors are much lower than those for hemophilia A (HA), which makes studies of inhibitors in patients with HB challenging due to the limited availability of samples. As a result, there is a knowledge gap regarding HB inhibitors. Objective Evaluate the largest group of patients with inhibitor-positive HB studied to date to assess the relationship between anti-FIX antibody profiles and inhibitor formation. Methods A fluorescence immunoassay was used to detect anti-FIX antibodies in plasma samples from 37 patients with HB. Results Assessments of antibody profiles showed that anti-FIX IgG1-4 , IgA, and IgE were detected significantly more often in patients with a positive Nijmegen-Bethesda assay (NBA). All NBA-positive samples were positive for IgG4 . Anti-FIX IgG4 demonstrated a strong correlation with the NBA, while correlations were significant, yet more moderate, for anti-FIX IgG1-2 and IgA. Conclusions The anti-FIX antibody profile in HB patients who develop inhibitors is diverse and correlates well with the NBA across immunoglobulin (sub)class, and anti-FIX IgG4 is particularly relevant to functional inhibition. The anti-FIX fluorescence immunoassay may serve as a useful tool to confirm the presence of antibodies in patients who have low positive NBA results and to more clearly define, predict, and treat alloantibody formation against FIX.

Evaluation of von Willebrand factor phenotypes and genotypes in Hemophilia A patients with and without identified F8 mutations.

BACKGROUND: Hemophilia A (HA) is an X-linked bleeding disorder caused by a deficiency in factor VIII (FVIII). von Willebrand disease (VWD) is characterized by a quantitative or qualitative defect in von Willebrand factor (VWF). Patients with VWD with severely low VWF or VWD Type 2N (VWD2N), a VWD subtype distinguished by defective VWF binding to FVIII, may have reduced FVIII levels secondary to their VWD. These patients superficially resemble patients with HA and pose a potential for misdiagnosis. OBJECTIVES: To investigate the unexplained cause of bleeding in HA patients without known FVIII mutations by assessing plasma VWF antigen (VWF:Ag), FVIII binding capacities and VWF genotypes. PATIENTS/METHODS: Thirty-seven of 1027 patients with HA studied as part of the Hemophilia Inhibitor Research Study lacked identifiable F8 mutations. These patients (cases) and 73 patients with identified F8 mutations (controls) were evaluated for VWF:Ag, a patient's VWF capacity to bind FVIII (VWF:FVIIIB) and VWF sequence. RESULTS: Four cases had VWF:Ag < 3 IU dL(-1) and VWF mutations consistent with Type 3 VWD. Six cases and one control were heterozygous for mutations previously reported to cause Type 1 VWD (VWD1) (n = five cases and one control) or predicted to be deleterious by Polyphen2 and SIFT prediction tools (n = 1 case). One control had VWF:Ag < 30 IU dL(-1) and seven patients (four cases and three controls), including two cases who were heterozygous for a known VWD2N mutation, had reduced VWF:FVIIIB. CONCLUSIONS: These data emphasize that some patients diagnosed with HA require VWF assessments in order to achieve a comprehensive diagnosis and an optimal treatment strategy.

Characterization of the anti-factor VIII immunoglobulin profile in patients with hemophilia A by use of a fluorescence-based immunoassay.

BACKGROUND: The development of neutralizing antibodies, referred to as inhibitors, against factor VIII is a major complication associated with FVIII infusion therapy for the treatment of hemophilia A (HA). Previous studies have shown that a subset of HA patients and a low percentage of healthy individuals harbor non-neutralizing anti-FVIII antibodies that do not elicit the clinical manifestations associated with inhibitor development. OBJECTIVE: To assess HA patients' anti-FVIII antibody profiles as potential predictors of clinical outcomes. METHODS: A fluorescence immunoassay (FLI) was used to detect anti-FVIII antibodies in 491 samples from 371 HA patients. RESULTS: Assessments of antibody profiles showed that the presence of anti-FVIII IgG1 , IgG2 or IgG4 correlated qualitatively and quantitatively with the presence of an FVIII inhibitor as determined with the Nijmegen-Bethesda assay (NBA). Forty-eight patients with a negative inhibitor history contributed serial samples to the study, including seven patients who had negative NBA titers initially and later converted to being NBA-positive. The FLI detected anti-FVIII IgG1 in five of those seven patients prior to their conversion to NBA-positive. Five of 15 serial-sample patients who had a negative inhibitor history and had anti-FVIII IgG1 later developed an inhibitor, as compared with two of 33 patients with a negative inhibitor history without anti-FVIII IgG1 . CONCLUSIONS: These data provide a rationale for future studies designed both to monitor the dynamics of anti-FVIII antibody profiles in HA patients as a potential predictor of future inhibitor development and to assess the value of the anti-FVIII FLI as a supplement to traditional inhibitor testing.

Laboratory testing for factor inhibitors.

Inhibitor assays are performed when patients present with unexplained prolonged routine coagulation test times and unexpected and/or unusual bleeding (potential for acquired haemophilia) as well as being a part of normal congenital haemophilia management and monitoring, particularly when bleeding occurs on therapy, or when increments in factor levels post-factor replacement remain lower than expected. In this article, we will describe the assays used, as well as their development, pitfalls in testing such as inter-laboratory variability and false negative/positive results, as well as some strategies for overcoming these pitfalls and potential alternative test approaches. The inter-laboratory coefficient of variation often approaches (and sometimes exceeds) 50%, as evidenced by various external quality assessment groups, and this variability has not improved over recent years. Additional important considerations include appropriate interpretation of test results, repeat testing for confirmation, and assessment of recovery as part of the diagnostic process.

A study of prospective surveillance for inhibitors among persons with haemophilia in the United States.

Inhibitors are a rare but serious complication of treatment of patients with haemophilia. Phase III clinical trials enrol too few patients to adequately assess new product inhibitor risk. This project explores the feasibility of using a public health surveillance system to conduct national surveillance for inhibitors. Staff at 17 U.S. haemophilia treatment centres (HTC) enrolled patients with haemophilia A and B into this prospective study. HTC staff provided detailed historic data on product use and inhibitors at baseline, and postenrolment patients provided monthly detailed infusion logs. A central laboratory performed inhibitor tests on blood specimens that were collected at baseline, annually, prior to any planned product switch or when clinically indicated. The central laboratory also performed genotyping of all enrolled patients. From January 2006 through June 2012, 1163 patients were enrolled and followed up for 3329 person-years. A total of 3048 inhibitor tests were performed and 23 new factor VIII inhibitors were identified, 61% of which were not clinically apparent. Infusion logs were submitted for 113,205 exposure days. Genotyping revealed 431 distinct mutations causing haemophilia, 151 of which had not previously been reported elsewhere in the world. This study provided critical information about the practical issues that must be addressed to successfully implement national inhibitor surveillance. Centralized testing with routine monitoring and confirmation of locally identified inhibitors will provide valid and representative data with which to evaluate inhibitor incidence and prevalence, monitor trends in occurrence rates and identify potential inhibitor outbreaks associated with products.

Comparison of clot-based, chromogenic and fluorescence assays for measurement of factor VIII inhibitors in the US Hemophilia Inhibitor Research Study.

BACKGROUND: Detection and validation of inhibitors (antibodies) to hemophilia treatment products are important for clinical care, evaluation of product safety and assessment of population trends. METHODS: Centralized monitoring for factor VIII (FVIII) inhibitors was conducted for patients in the Hemophilia Inhibitor Research Study using a previously reported modified Nijmegen-Bethesda clotting assay (NBA), a chromogenic Bethesda assay (CBA) and a novel fluorescence immunoassay (FLI). RESULTS: NBA and CBA were performed on 1005 specimens and FLI on 272 specimens. CBA was negative on 880/883 specimens (99.7%) with Nijmegen-Bethesda units (NBU) < 0.5 and positive on 42/42 specimens (100%) with NBU ≥ 2.0 and 43/80 specimens (53.8%) with NBU 0.5-1.9. Among specimens with positive NBA and negative CBA, 58.1% were FLI negative, 12.9% had evidence of lupus anticoagulant, and 35.5% had non-time-dependent inhibition. CBA and FLI were positive on 72.4% and 100% of 1.0-1.9 NBU specimens and 43.1% and 50.0% of 0.5-0.9 NBU specimens. FLI detected antibodies in 98.0% of CBA-positive and 81.6% of NBA-positive specimens (P = 0.004). Among 21 new inhibitors detected by NBA, five (23.8%) with 0.7-1.3 NBU did not react in CBA or FLI. Among previously positive patients with 0.5-1.9 NBU, 7/25 (28%) were not CBA or FLI positive. FLI was positive on 36/169 NBU-negative specimens (21.3%). CONCLUSIONS: FVIII specificity could not be demonstrated by CBA or FLI for 26% of inhibitors of 0.5-1.9 NBU; such results must be interpreted with caution. Low titer inhibitors detected in clot-based assays should always be repeated, with consideration given to evaluating their reactivity with FVIII using more specific assays.

Validation of Nijmegen-Bethesda assay modifications to allow inhibitor measurement during replacement therapy and facilitate inhibitor surveillance.

BACKGROUND: As part of a pilot U.S. inhibitor surveillance project initiated at the Centers for Disease Control and Prevention (CDC) in 2006, a centralized inhibitor measurement was instituted. OBJECTIVE: To validate a modified method for inhibitor measurement suitable for surveillance of treated and untreated patients. METHODS/RESULTS: In all, 710 subjects with hemophilia A were enrolled; 122 had a history of inhibitor (HI). Nijmegen-Bethesda assay (NBA) results on 50 split specimens shipped on cold packs and frozen were equivalent (r=0.998). Because 55% of 228 initial specimens had factor (F)VIII activity (VIII:C) present, a heat treatment step was added. Heating specimens to 56°C for 30 min and centrifuging removed FVIII, as demonstrated by a reduction of VIII:C and FVIII antigen to <1 U dL(-1) in recently treated patients. Among specimens inhibitor-negative before heating, one of 159 with negative HI and five of 30 with positive HI rose to ≥ 0.5 Nijmegen-Bethesda units (NBU) after heating. Correlation of heated and unheated inhibitor-positive specimens was 0.94 (P=0.0001). The modified method had a coefficient of variation (CV) for a 1 NBU positive control of 10.3% and for the negative control of 9.8%. Based on results on 710 enrollment specimens, a positive CDC inhibitor was defined as ≥ 0.5 NBU. Results were similar when 643 post-enrollment specimens were included. Of 160 enrolled hemophilia B patients, two had HI. All others had NBU ≤ 0.2 at enrollment. CONCLUSION: The CDC experience demonstrates that this modified NBA can be standardized to be within acceptable limits for clinical tests and can be used for national surveillance.

F8 and F9 mutations in US haemophilia patients: correlation with history of inhibitor and race/ethnicity.

Both genetic and treatment-related risk factors contribute to the development of inhibitors in haemophilia. An inhibitor surveillance system piloted at 12 US sites has the goal of assessing risk factors through prospective data collection. This report examines the relationship of genotype and race/ethnicity to history of inhibitor in a large cohort of US haemophilia patients. Mutation analysis was performed on 676 haemophilia A (HA) and 153 haemophilia B (HB) patients by sequencing, Multiplex Ligation-dependent Probe Amplification, and PCR for inversions in F8 introns 22 (inv22) and 1 (inv1). Two HB patients with deletions had history of inhibitor. In severe HA, frequency of history of inhibitor was: large deletion 57.1%, splice site 35.7%, inv22 26.8%, nonsense 24.5%, frameshift 12.9%, inv1 11.1% and missense 9.5%. In HA, 19.6% of 321 White non-Hispanics (Whites), 37.1% of 35 Black non-Hispanics (Blacks) and 46.9% of 32 Hispanics had history of inhibitor (P = 0.0003). Mutation types and novel mutation rates were similar across ethnicities. When F8 haplotypes were constructed, Whites and Hispanics showed only H1 and H2. Within H1, history of inhibitor was 12.4% in Whites, 40.0% in Blacks (P = 0.009) and 32.4% in Hispanics (P = 0.002). Inhibitor frequency is confirmed to vary by mutation type and race in a large US population. White patients with history of inhibitor did not exhibit rare F8 haplotypes. F8 gene analysis did not reveal a cause for the higher inhibitor frequencies in Black and Hispanic patients.

The spectrum of haemostatic characteristics of women with unexplained menorrhagia.

While an estimated 13% of women with unexplained menorrhagia have von Willebrand disease (VWD), the frequency of other potential bleeding disorders has been uncertain. This study describes the relatively wide range of laboratory characteristics of women with unexplained menorrhagia and presents issues affecting diagnosis in this population. Women with pictorial blood assessment chart (PBAC) score > 100 were identified at six U.S. sites and asked to remain drug free for 10 days prior to testing. Blood was collected on one of the first four menstrual cycle days and tested at a central laboratory for procoagulant factors, VWD and fibrinolytic factors. Platelet function testing by PFA-100® (PFA) and platelet aggregation with ATP release (PAGG/ATPR) were performed locally using standardized methods. Among 232 subjects, a laboratory abnormality was found in 170 (73.3%), including 124 of 182 White (68.1%) and 34 of 37 Black (91.9%) subjects; 6.0% had VWD, 56.0% had abnormal PAGG/ATPR, 4.7% had a non-VWD coagulation defect (NVCD) and 6.5% had an abnormal PFA only. AGG/ATPR was reduced in 58.9% of subjects, with multiple agonists in 28.6%, a single agonist in 6.1% and ristocetin alone in 24.2%. Frequencies of PAGG/ATPR defects varied by study site and race; frequencies of VWD and NVCD were similar. Laboratory abnormalities of haemostasis, especially platelet function defects, were common among women with unexplained menorrhagia across multiple U.S. sites. To what degree these abnormalities are clinically significant requires further study.

In non-severe hemophilia A the risk of inhibitor after intensive factor treatment is greater in older patients: a case-control study.

BACKGROUND: Twenty-five percent of new anti-factor VIII (FVIII) antibodies (inhibitors) that complicate hemophilia A occur in those with mild and moderate disease. Although intensive FVIII treatment has long been considered a risk factor for inhibitor development in those with non-severe disease, its strength of association and the influence of other factors have remained undefined. OBJECTIVE: To evaluate risk factors for inhibitor development in patients with non-severe hemophilia A. METHODS: Information on clinical and demographic variables and FVIII genotype was collected on 36 subjects with mild or moderate hemophilia A and an inhibitor and 62 controls also with mild or moderate hemophilia A but without an inhibitor. RESULTS: Treatment with FVIII for six or more consecutive days during the prior year was more strongly associated with inhibitor development in those ≥30years of age compared with those <30years of age [adjusted odds ratio (OR) 12.62; 95% confidence interval (CI), 2.76-57.81 vs. OR 2.54; 95% CI, 0.61-10.68]. Having previously received <50days of FVIII was also not statistically associated with inhibitor development on univariate or multivariate analysis. CONCLUSIONS: These findings suggest that inhibitor development in mild and moderate hemophilia A varies with age, but does not vary significantly with lifetime FVIII exposure days: two features distinct from severe hemophilia A.

Laboratory response to intranasal desmopressin in women with menorrhagia and platelet dysfunction.

Intranasal desmopressin (IN-DDAVP) is used for home treatment of menorrhagia in women with inherited bleeding disorders. The effect of IN-DDAVP on laboratory haemostatic parameters in women with menorrhagia related to platelet dysfunction is unknown. We evaluated the effects of IN-DDAVP on haemostatic parameters in women with menorrhagia and platelet dysfunction and correlated them with menstrual flow. Eleven women (aged 18-45) with menorrhagia and haemostatic abnormalities had determination of von Willebrand factor antigen (VWF:Ag), von Willebrand factor ristocetin cofactor (VWF:RCo) activity, factor VIII coagulant activity (FVIII:C), platelet aggregation and platelet adenosine tri-phosphate (ATP) release pre-IN-DDAVP and 60-min post-IN-DDAVP. Eight of eleven women underwent platelet function analyzer (PFA-100) closure time determination with collagen/adrenaline and collagen/adenosine diphosphate cartridges pretreatment and post-treatment. IN-DDAVP was administered during two consecutive menstrual cycles. Menstrual flow was assessed during each cycle using a pictorial blood assessment chart. Treatment with IN-DDAVP resulted in elevated VWF levels and shortened PFA-100 closure time with significant inverse correlation between shortening of PFA-100 closure times and increases in VWF levels. There were also significant inverse correlations between changes in menstrual flow and changes in VWF:Ag (P = 0.02), VWF:RCo (P = 0.04) and FVIII:C (P = 0.006), following treatment. In vitro platelet aggregation and platelet ATP release response did not correct and did not correlate with changes in menstrual flow. Our results demonstrate a correlation between haemostatic parameters and menstrual flow following IN-DDAVP in women with menorrhagia and platelet dysfunction.