The rapid Bethesda assay is equivalent to the standard Bethesda assay for detection of factor IX inhibitors in patients with severe haemophilia B.

INTRODUCTION: The time-dependent nature of factor VIII (FVIII) inhibitors is well described, and the standard FVIII Bethesda assay used to measure inhibitors incorporates a 2-hour incubation. Despite case reports and reviews describing the immediate-acting nature of factor IX (FIX) inhibitors, many coagulation laboratories continue to use a traditional prolonged incubation for FIX Bethesda assays. To our knowledge, a comprehensive evaluation of the FIX Bethesda assay without incubation has not been reported. AIM: The goal of this study was to evaluate the performance of a rapid FIX Bethesda (ie no incubation) compared with the standard Bethesda assay (2-hour incubation). METHODS: The analysis used a Bethesda assay configured for either immediate testing or a 2-hour incubation. Samples from 14 haemophilia B patients with inhibitors and 9 non-human controls were tested. RESULTS: The two assays yielded similar performance overall. The average per cent difference in inhibitor titre between the rapid and standard FIX Bethesda assay was -3% (range -15% to +13%; P = .175) for patient samples and -2% (range -17% to +14%; P = .376) for controls. CONCLUSION: The rapid Bethesda assay showed good agreement with the standard Bethesda assay for determination of inhibitor levels in patients with severe haemophilia B. The rapid assay allows for faster assessment of inhibitors in patients with severe haemophilia B and has the potential to improve the ability of the coagulation laboratory to perform testing from a logistical viewpoint. Further studies involving larger numbers of patients would be important to confirm our findings.

Mixing-based inhibitor screening in haemophilia A: challenges in interpretation.

: Inhibitor development in haemophilia A patients is a dreaded complication of factor VIII (FVIII) replacement therapy. With increasing use of FVIII replacement therapy, there is an imperative need for cost-effective and standardized screening. To evaluate the efficacy of mixing-based inhibitor screening (MBIS) in the detection of FVIII inhibitors and to assess the best cut-off values for MBIS. Forty inhibitor positive and 40 inhibitor negative haemophilia A patients, diagnosed by standard criteria, with detailed clinical, haematological and on-demand treatment records were included. MBIS was evaluated in all 80 cases and a classical Bethesda assay and Nijmegen modification of Bethesda assay (NBA) were used as gold standards for inhibitor diagnosis. Classical Bethesda assay missed eight cases, most with low titres, which were confirmed by NBA. A systematic analysis of cut-offs for MBIS using a receiver operating characteristic curve fixed the cut-off at more than 5 s. MBIS detected 36 out of 40 inhibitor positive haemophilia A patients with a sensitivity, specificity, PPV and NPV of 90.0, 95, 94.7, 90.5%, respectively, whereas at the conventional cut-off of more than 10 s, MBIS detected only 25 of 40 cases with a low sensitivity of 62.5%. The likelihood ratio of a positive test was 11. The false-negative haemophilia A patients had low titres from 1.6 to 4.2 BU/ml. MBIS at a cut-off of 5 s can be considered as an effective screening test in low-resource situations. In clinical situations and in cases with clinical evidence of inhibitors we recommend that a direct NBA should be done.

A Comparison of Hemostatic Changes in Splenectomized and Nonsplenectomized ß-Thalassemia Intermedia Patients.

The present study was conducted to compare the coagulation factors between splenectomized and nonsplenectomized thalassemia intermedia (TI) patients as well as a healthy control group. A total of 60 splenectomized and 60 nonsplenectomized TI patients and 60 healthy controls participated in this case-control study. The level of homocysteine, protein C and S, antithrombin III, factors V and VIII, fibrinogen, and D-dimer were measured in all groups. Our results indicated a significant reduction of protein C and S and fibrinogen in TI patients compared with healthy controls (P<0.001), as well as factor V activity (P=0.009). Also a significant elevation of D-dimer (P=0.006) and factor VIII activity (P=0.001) was observed. There was no significant difference considering homocysteine and antithrombin III level among patients and healthy controls. Also our results demonstrated that there was no significant difference considering the homeostatic parameters (except D-dimer activity) between splenectomized and nonsplenectomized TI patients after adjustment for age. In conclusion, reduction of protein C and S, fibrinogen, and factor V activity and elevation of D-dimer levels and factor VIII activity was observed in TI patients compared with healthy controls. It seems that splenectomy has little significant effect on concentration of hemostatic factors except for D-dimer activity.

A variation of the Nijmegen-Bethesda assay using heat or a novel heat/cold pretreatment for the detection of FIX inhibitors in the presence of residual FIX activity.

INTRODUCTION: The inclusion of a heat treatment step has improved the classic Nijmegen-Bethesda assay for detection of factor VIII (FVIII) inhibitors in the presence of residual FVIII activity (FVIII:C). However, information regarding heat-modified Nijmegen-Bethesda assays for the detection of FIX inhibitors is still limited. METHODS: Three methods to measure FIX inhibitors in the presence or absence of residual FIX activity (FIX:C) using three different activated partial thromboplastin time (aPTT) reagents were investigated. These included the standard Nijmegen-Bethesda assay (method 1), a heat-modified assay (method 2) and a novel heat/cold-modified assay (method 3). RESULTS: In the absence of FIX:C, all methods measured similar levels of FIX inhibitor, while FIX inhibitor titres varied widely in the presence of residual FIX:C. Using method 1, inhibitors were not accurately measured in the presence of residual circulating FIX:C. Using method 2, detection was improved, especially at higher inhibitor titres. Using method 3, some additional sensitivity was obtained. The choice of aPTT reagent did not affect the detection of inhibitors. CONCLUSION: Heat pretreatment is recommended for detecting FIX inhibitors in samples with residual FIX:C. The heat/cold modification improved the sensitivity of the Nijmegen-Bethesda assay, resulting in higher tolerance for residual FIX:C.

Biochemical characterization of prothrombin complex concentrates in China.

Despite increasing use of prothrombin complex concentrates (PCCs), there is little knowledge about the biochemical characterization of Chinese PCCs. Six Chinese PCCs were investigated and compared with PCCs (Octaplex®) from Europe. The levels of coagulation factors and inhibitors were detected. The presence of activated coagulation factors was assessed. Furthermore, their thrombin inhibitory capacities, specific activity and purity were assayed. All above parameters of biochemical properties were statistically analyzed. Chinese PCCs contained FⅡ, Ⅶ, Ⅸ and Ⅹ, protein C, S and Z, heparin and extremely low level antithrombin, as well as Octaplex®. The measured FⅨ activities were similar to those declared, however the measured potency of FⅡ, Ⅶ and Ⅹ greatly exceeded the labeled. Though all preparations were negative for activated coagulation factors in non-activated partial thromboplastin time test, the activated coagulation factor Ⅶ (FⅦa) remained in all PCCs and its content differed greatly. Overall, FⅦa content of Chinese PCCs was higher than that of Octaplex®. Further, Chinese PCCs were inferior to Octaplex® in the thrombin inhibitory capacities, specific activity and purity. In summary, compared with Octaplex®, Chinese PCCs' errors about the labeled activity of coagulation factors and probably high risks of thrombosis should be considered.

Coagulation factors and inhibitors in thawed plasma stored at 1-6 °C for 5 days in China.

INTRODUCTION: Many transfusion services are keeping thawed plasma (TP) ready for trauma patients. According to Chinese guidelines, once thawed, fresh frozen plasma (FFP) should be used within 24h. This may increase plasma wastage and delay plasma administration to critical patients. However, it can be avoided by being relabeled as TP. In this study we evaluated coagulation-related proteins in thawed apheresis FFP during 5 days of storage at 1-6 °C. MATERIALS AND METHODS: Thirty apheresis fresh plasma units were aliquot and stored at -70 °C. Aliquots were thawed at 37 °C and stored at 1-6 °C for 0, 1, 2, 3, 4 and 5 days, respectively. Prothrombin time (PT), activated partial thromboplastin time (aPTT), thrombin time (TT), fibrinogen (Fbg), factor (F) II, FV, FVII, FVIII, FIX, FX, FXI, FXII, protein C (PC), protein S (PS), antithrombin III (ATIII) and ADAMTS13 levels were assessed at Days 0-5, respectively. RESULTS: For 5 days of refrigerated storage, no significant differences were observed in Fbg, PC, PS, ATIII and ADAMTS13. FII, FV, FVII, FVIII, FIX, FX, FXI and FXII declined significantly over time. The storage presented major decrease for FVIII, with a drop of 40%. However, at least 60% levels of all measured proteins were remained on Day 5, when compared to Day 0. CONCLUSION: All measured proteins in TP for 5 days of refrigerated storage were adequate. These could provide evidence that thawed FFP could be relabeled as TP, which is a potential to ensure rapid plasma availability in emergency situations in China.

Validation of 4% albumin as a diluent in the Bethesda Assay for FVIII inhibitors.

INTRODUCTION: External quality assurance programs show the Nijmegen Bethesda Assay for FVIII inhibitors improves test specificity compared to the Classic Bethesda Assay but its uptake has been slow possibly due to the cost of using FVIII deficient plasma as diluent. This study was conducted to determine if modifying the Nijmegen Bethesda assay by replacement of FVIII deficient plasma with 4% as a diluent would be suitable for for measuring FVIII inhibitors. MATERIALS AND METHODS: The titres of 59 samples from 35 patients with FVIII inhibitors were determined in parallel tests by the Nijmegen Bethesda Assay and and the modified Nijmegen assay. Method reproducibility was assessed on inhibitor-containing samples from seven individuals covering a range of titres from 1-200 Bethesda units/mL. RESULTS: The all-sample geometric mean titre was 6.73 Bethesda units/mL for the Nijmegen Bethesda Assay and 7.54 Bethesda units/mL for the modified Nijmegen assay. No sample was found where a difference in measured titre between methods would have altered clinical management. Agreement was very close in samples with titres less than 2BU/mL. Both assays gave inhibitor titres in external quality assurance samples of close to consensus values. The average between-run coefficients of variation were 8.6% for the Nijmegen Bethesda Assay and 7.9% for the modified Nijmegen assay. CONCLUSIONS: The modified Nijmegen assay using 4% albumin as the sample diluent showed good overall comparability to our existing Nijmegen Bethesda Assay and is substantially more cost-effective, making it a reasonable alternative for measuring FVIII inhibitors.

Laboratory identification of factor inhibitors: an update.

Coagulation factor inhibitors comprise antibodies that bind to and then neutralise specific pro-coagulant plasma proteins. Coagulation factor inhibitors can develop against any coagulation factor, although the most common are against factor VIII (FVIII). These can develop in individuals with inherited haemophilia A (HA) as an immune response to factor replacement therapy, or as auto-antibodies leading to the condition of acquired HA. Clinical suspicion for inhibitors may arise when individuals present with bleeding symptoms without any prior bleeding diathesis, or when a patient with known mild haemophilia presents with a bleeding diathesis more extreme to their usual presentation, or when there is failure of factor replacement therapy to arrest bleeding in a known haemophiliac. The laboratory identification of factor inhibitors requires a careful and systematic approach that excludes other possible causes of prolonged screening tests, most commonly the activated partial thromboplastin time (APTT), and sometimes prothrombin time (PT). Coagulation factor inhibitor studies, including the Bethesda assay, are then undertaken to measure inhibitor titre, which guides treatment. This paper overviews the laboratory investigation of factor inhibitors, and also briefly reviews recent cross-laboratory inhibitor studies and the most recent evidence related to differential inhibitor formation according to type of therapy.

Cost effectiveness of prophylactic treatment with activated prothrombin complex concentrate in a patient with inhibitor-positive hemophilia A.

Patients with hemophilia and high titers of inhibitors are hard to treat during bleeding events and consequently are more likely to incur high treatment costs and to experience deterioration in quality of life. We report here the case of a boy with hemophilia A and high titers of inhibitors who responded well to prophylactic activated prothrombin complex concentrate (APCC) treatment. Previously, he had to be hospitalized frequently because of painful bleeding of target joints of the knee and ankle. At the age of 4 years and 3 months, APCC prophylaxis at a dose of 60 U/kg, three times a week, was initiated together with on-demand therapy with recombinant factor VIIa. This reduced the frequency and severity of bleeding and ended the need for hospitalization. This, together with a decreased requirement for bypass agents, APCC treatment significantly reduced the cost of treatment for this patient.

Recommendations for assessment, monitoring and follow-up of patients with haemophilia.

Over the last few decades, clinical follow-up of patients with haemophilia has become more complex as a result of the introduction of new treatment strategies, the presence of comorbidities related to haemophilia or ageing, as well as the emergence of new tools to evaluate the medical and social consequences of haemophilia. This publication describes the parameters and information that should be documented and the tests, examinations and interventions required for optimal follow-up of a patient with haemophilia. In the absence of formal studies, the present recommendations have been established as result of a series of consensus meetings in the frame of the European Haemophilia Therapy Standardization Board (EHTSB). The following 11 domains were identified: Baseline information, Current status, Treatment, Inhibitor status, Bleeding, Joint status and pain, Comorbidities, Dental care, Physical activities, Social participation and Quality of life. For each domain, details are proposed for the relevant parameters to be captured and monitored as well as the relevant tools that facilitate data collection. Adopting these recommendations should help the individual care of patients and, even though this is not the primary objective of this article, it should also help at national and international level to shape a new approach to haemophilia by working towards a more standardized outcome assessment. Greater standardization should have implications for data collection, improvements in treatment evaluation and optimizing resources.

Healthcare resource utilization among haemophilia A patients in the United States.

Advances in therapy have improved life expectancy and quality of life of patients with haemophilia A. Due to the chronic and complex management of this disease, particularly, the development of inhibitors, little is known about their health resource utilization in the real-life setting over time. The aim was to assess the distribution and trend of healthcare resource utilization among US haemophilia A patients with and without inhibitors. The MarketScan® Database, was queried to identify individuals with ≥1 year continuous enrolment, two medical diagnoses of haemophilia A and claims for factor VIII or bypassing agent (to infer inhibitor status) during 2001-2007. Haemophilia-related cost was estimated from inpatient, outpatient and pharmacy claims. Annual cost differences were assessed by age and over a 4-year period for those with continuous enrolment. Among 51 million covered lives, 1044 haemophilia patients were identified, of whom 981 (94%; mean age = 21.2 years) did not have an inhibitor. The median haemophilia-related cost for these patients was $63,935 per patient per year. When normalized by weight, annual cost was stable (no statistically significant differences) among 312 non-inhibitor patients (mean age = 21.8 years) with 4-year continuous data. While there was a wide distribution of haemophilia-related cost among the 63 individuals with an inhibitor (mean age = 15.4 years), only 0.6% of the total haemophilia patients had costs exceeding $1 million per patient per year. This study indicated that most haemophilia A patients were inhibitor-free with relatively stable annual costs over time. There was a wide distribution of haemophilia-related cost for inhibitor patients, while the proportion of patients who incurred extreme high cost was low.

Cumulative inhibitor incidence in previously untreated patients with severe hemophilia A treated with plasma-derived versus recombinant factor VIII concentrates: a critical systematic review.

Inhibitor development represents currently the most serious and challenging complication of clotting factor replacement therapy. A number of studies have analyzed the impact of the type of factor VIII (FVIII) replacement therapy (plasma-derived versus recombinant concentrates) on inhibitor development in hemophilia A patients with conflicting results. In order to shed light on this controversial issue, we performed a systematic review and meta-analysis on the published prospective studies evaluating the incidence rate of inhibitors in previously untreated patients (PUPs) with severe hemophilia A. Data from a total of 800 patients enrolled in 25 prospective studies published between 1990 and 2007 were included in this review. The quality of the studies was evaluated using two different systems: the Newcastle-Ottawa Scale (NOS) and STrengthening the Reporting of OBservational studies in Epidemiology (STROBE). Overall, the inhibitor incidence rate did not differ significantly between recipients of plasma-derived and recombinant FVIII concentrates (weighted means: 21%; 95% CI, 14-30 versus 27%; 95% CI, 21-33). Similarly, high titer inhibitors did not differ significantly between patients treated with plasma-derived (weighted means: 14%; 95% CI, 8-25) or recombinant FVIII concentrates (weighted means: 16%; 95% CI, 13-20). Thus, the main conclusion of this systematic review performed using selective criteria is that the type of FVIII product (i.e., plasma-derived versus recombinant FVIII concentrates) does not seem to influence the inhibitor rate in PUPs with severe hemophilia A.

Validity of assessing inhibitor development in haemophilia PUPs using registry data: the EUHASS project.

Inhibitory antibodies to exogenous FVIII/FIX are a major complication of haemophilia treatment. Up to 30% of previously untreated patients (PUPs) with severe haemophilia A develop inhibitors, most likely during the initial 50 exposure days to concentrate. In addition to classical cohort studies, a European monitoring system (EUHASS) has been set up to evaluate inhibitor development in PUPs. The present study addresses the reliability of estimating the cumulative incidence of inhibitor development in this registry. Data from the retrospective CANAL cohort study, including 288 PUPs with severe haemophilia A and complete treatment records until the 50th exposure to FVIII, were used to simulate the consequences of several cross-sectional sampling techniques on the estimated incidence of inhibitors. Both mathematical calculus and computer modelling were applied to study the effects of sample size and the introduction of a new product. For existing concentrates, both longitudinal cohort study methods and the EUHASS method yielded similar estimates of the cumulative incidence of inhibitor cases over a 5-year time period: 27.9% (95% CI: 21-36) vs. 29.4% (22-38). For a newly introduced concentrate, a reliable estimate of inhibitor incidence with the EUHASS method could only be made after 3-4 years, even in large datasets. The results from EUHASS in inhibitor incidence in PUPs are expected to be valid. After introduction of a new concentrate, the inhibitor incidence on this concentrate can only be reliably determined after an observation period of several years.

Assessing the impact of age, race, ethnicity and inhibitor status on functional limitations of patients with severe and moderately severe haemophilia A.

Few data exist on the impact of age and inhibitor status on activity levels among patients with severe and moderately severe haemophilia A. The aim of this analysis was to assess the impact of age, race/ethnicity and inhibitor status on functional limitations through retrospective analysis of data from the Hemophilia and Thrombosis Research Society (HTRS) Registry. Functional status data from patients with haemophilia A with or without inhibitors who were enrolled in the HTRS Registry between October 1999 and July 2008 were analysed by age, race and ethnicity. Of the 2497 registrants, 1340 had congenital haemophilia A (333 with inhibitors). Functional status was available for 274 subjects with haemophilia A with current inhibitors and 247 subjects without inhibitors who had moderately severe (FVIII levels ≤ 2%). Functional impairment increased with age across five levels of functional status (P < 0.01). Inhibitors were associated with greater functional impairment in two age groups (13-21 years and older than 21 years) [unrestricted activity in 57.8% vs. 63.6% (P = 0.06) and 18.3% vs. 28.6% (P = 0.04), respectively]. Blacks had worse functional status than caucasians across all ages regardless of inhibitor status. Functional status decreases with age, and impairment is greater among patients with inhibitors beginning in adolescence. These results reaffirm the need for early eradication of inhibitors and early treatment of bleeds in inhibitor and non-inhibitor patients. This analysis highlights the benefit of ongoing study of these patients through data collected for the HTRS Registry.

Haemophilia A and von Willebrand's disease.

SUMMARY: Deficient or defective coagulation factor VIII (FVIII) and von Willebrand factor (VWF) can cause bleeding through congenital deficiency or acquired inhibitory antibodies. Recent studies on type 1 von Willebrand's disease (VWD), the most common form of the disease, have begun to explain its pathogenesis. Missense mutations of varying penetrance throughout VWF are the predominant mutation type. Other mutation types also contribute while about one-third of patients have no mutation identified. Enhanced clearance and intracellular retention contribute to pathogenic mechanisms. Chromogenic substrate (CS) methods to determine FVIII coagulant activity have several advantages over one-stage methods, which include minimal influence by variable levels of plasma components, notably lupus anticoagulant. Direct proportionality between FVIII activity and FXa generation results in high resolution at all FVIII levels, rendering the CS method suitable for measuring both high and low levels of FVIII activity. FVIII inhibitors in patients with inherited or acquired haemophilia A present several challenges in their detection and accurate quantification. The Nijmegen method, a modification of the Bethesda assay is recommended for inhibitor analysis by the International Society on Thrombosis and Haemostasis. Understanding potential confounding factors including heparin and residual FVIII in test plasma, plus optimal standardization can reduce assay coefficient of variation to 10-20%.These areas are all explored within this article.

Comparative measurement of FVIII inhibitors in hemophilia A patients using ELISA and the Bethesda assay.

Factor VIII inhibitors are produced during or after coagulation factor VIII (FVIII) therapy in hemophilia A patients. These inhibitors are usually detected by a modified Bethesda assay or an enzyme-linked immunosorbent assay (ELISA). In this study, we used the Bethesda assay to determine the incidence of FVIII inhibitors in 75 fresh plasma samples obtained from 50 hemophilia A patients, and then used ELISA and the Bethesda assay to determine the titres of these inhibitors after the samples had been frozen and thawed. The samples from the screening Bethesda assay were centrifuged and stored at -70 degrees C in accordance with the assay guidelines. Subsequently, these samples were thawed and analyzed using ELISA and the Bethesda assay. The incidence of inhibitors in hemophilia A patients was 20.0%. Among the 35 inhibitor-positive samples identified in the screening Bethesda assay, 16 were positive in ELISA while only 4 were positive in the repeated Bethesda assay. In this study, the ELISA technique showed a higher sensitivity than the Bethesda assay in the detection of FVIII inhibitors in samples that were subjected to freezing and thawing procedures; this was because the Bethesda assay could not identify the FVIII inhibitors that were degraded after freezing and thawing.