This systematic review was designed to provide more precise effect estimates of inhibitor development for the various types of F8 gene mutations in patients with severe hemophilia A. The primary outcome was inhibitor development and the secondary outcome was high-titerinhibitor development. A systematic literature search was performed to include cohort studies published in peer-reviewed journals with data on inhibitor incidences in the various F8 gene mutation types and a mutation detection rate of at least 80%.

Summary.  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.

Summary. Menorrhagia is a common clinical problem and is unexplained in more than 50% of women. Although studies suggest that von Willebrand's Disease (VWD) is found in a substantial number of women with unexplained menorrhagia, the prevalence of platelet defects in women with menorrhagia is unknown. To determine the prevalence of platelet and other hemostatic defects, we evaluated women ages 17-55 diagnosed with unexplained menorrhagia. Seventy-four women (52 white, 16 black, six other) were studied. Bleeding time was prolonged in 23 women (31.5%). Maximal percent platelet aggregation was decreased with one or more agonists in 35 (47.3%) women. The most commonly found platelet function defects were reduced aggregation responses to ristocetin in 22 women and to epinephrine in 16 women. Sixteen of 22 women with reduced ristocetin aggregation had von Willebrand ristocetin cofactor (VWF:RCo) and von Willebrand factor antigen (VWF:Ag) > 60%. Platelet ATP release was decreased with one or more agonists in 43 (58.1%) women. Of the black women studied, 11/ 16 (69%) had abnormal platelet aggregation studies compared with 20/52 white women (39%) (P ¼ 0.06). Black women with menorrhagia had a higher prevalence of decreased platelet aggregation in response to ristocetin and epinephrine than did white women (P ¼ 0.0075, P ¼ 0.02). Ten women (13.5%) had VWF:RCo and/or VWF:Ag < 60%. Using race and blood group specific ranges, 5 (6.8%) women had decreased VWF:RCo, VWF:Ag and/or collagen binding (VWF:CB). Mild factor XI deficiency was found in two women and one woman with mild factor V deficiency and one hemophilia A carrier were identified. We conclude that the prevalence of platelet function defects and other inherited bleeding disorders is substantial in a multiracial US population of women with unexplained menorrhagia.

The prevalence of inherited bleeding disorders among white women with menorrhagia was substantial, consistent with European data published recently. For unknown reasons, the prevalence of von Willebrand disease was lower among black women. These findings indicate the importance of considering inherited bleeding disorders as a cause of menorrhagia.

The previously published mortality studies are limited in hemophilia populations but suggest that there is no increased risk of mortality in factor VIII inhibitor patients. This retrospective study analyzed surveillance data collected on 7,386 males with severe hemophilia A over a 13-year period to assess the association between a current inhibitor and death. During the study period, 432 participants died, among whom 48 were patients with an inhibitor. Clinical characteristics most strongly associated with death were increased number of reported bleeds, signs of liver disease, infection with either HIV or HCV, and the presence of inhibitor. Patients who underwent successful tolerization were not considered inhibitor patients in our analysis. In a multivariable analysis, the odds of death were 70% higher among patients with a current inhibitor compared to those without an inhibitor (P < 0.01). Deaths among patients with inhibitors were much more likely to be attributed to bleeding complications than those among patients without an inhibitor (42 vs. 12%, P < 0.0001). We conclude that males with severe hemophilia A and a current inhibitor are at increased risk of death.

Summary. Tests based on three different principles are reported to measure the activity of von Willebrand factor (VWF): ristocetin cofactor (VWF:RCo), collagen binding (VWF:CB), and the so-called`activity ELISA' (VWF:MoAb). We measured these and other diagnostic parameters in a population of 123 randomly selected female study controls, age 18±45 years. Type O subjects had signi®cantly lower levels than non-O subjects in each test. Race differences were seen in all tests except VWF:RCo, with Caucasians having signi®cantly lower levels than African-Americans. ABO differences accounted for 19% of the total variance in VWF:Ag (P < 0.0001) and race for 7% (P < 0.0001), for a total of 26%. Both effects were mediated through VWF:Ag and were independent. VWF:Ag level was the primary determinant of VWF function, accounting for approximately 60% of the variance in VWF:RCo and VWF:CB and 54% of the variance in factor VIII. The ratio VWF:RCo/ VWF:Ag differed signi®cantly by race within blood group. The median ratios were 0.97 for type O Caucasians vs. 0.79 for type O African-Americans and 0.94 for non-O Caucasians vs. 0.76 for non-O African-Americans. The ratio VWF:CB/VWF:Ag did not vary. This suggests racial differences in the interaction of VWF with GP1b but not with subendothelium. Alternatively, VWF:RCo may be regulated to maintain a relatively constant plasma level in the presence of excessive VWF:Ag. This heterogeneity within the normal population is partially responsible for the dif®culty in de®ning diagnostic limits for von Willebrand disease.

Summary 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, 5 (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.

II-2.