To cite this article: Boender J, Kruip MJHA, Leebeek FWG. A diagnostic approach to mild bleeding disorders. J Thromb Haemost 2016; 14:1507-16.Summary. Mild inherited bleeding disorders are relatively common in the general population. Despite recent advances in diagnostic approaches, mild inherited bleeding disorders still pose a significant diagnostic challenge. Hemorrhagic diathesis can be caused by disorders in primary hemostasis (von Willebrand disease, inherited platelet function disorders), secondary hemostasis (hemophilia A and B, other (rare) coagulant factor deficiencies) and fibrinolysis, and in connective tissue or vascular formation. This review summarizes the currently available diagnostic methods for mild bleeding disorders and their pitfalls, from structured patient history to highly specialized laboratory diagnosis. A comprehensive framework for a diagnostic approach to mild inherited bleeding disorders is proposed.

The bleeding phenotype of children with von Willebrand disease (VWD) needs to be characterized in detail to facilitate diagnosis during childhood and aid in the planning and assessment of treatment strategies. The objective was to evaluate the occurrence, type, and severity of bleeding in a large cohort of children with moderate and severe VWD. We included 113 children (aged 0-16 years) with Type 1 (n 5 60), 2 (n 5 44), and 3 (n 5 9) VWD with von Willebrand factor (VWF) antigen and/or VWF ristocetin cofactor levels 30 U/dL from a nation-wide cross-sectional study ("Willebrand in the Netherlands" study). Bleeding severity and frequency were determined using the International Society on Thrombosis and Hemostasis-Bleeding Assessment Tool (ISTH-BAT) with supplementary pediatric-specific bleeding symptoms (umbilical stump bleeding, cephalohematoma, cheek hematoma, conjunctival bleeding, postcircumcision and postvenipuncture bleeding). We found that all 26 postmenarche girls experienced menorrhagia. Other common bleedings were cutaneous (81%), oropharyngeal (64%), prolonged bleeding from minor wounds (58%), and epistaxis (56%). Pediatric-specific bleeding symptoms were present in 44% of patients. ISTH-BAT bleeding score was higher in index cases than in affected family members (median, 12.0 vs. 6.5, P < 0.001), higher in Type 3 VWD than in Type 2 or 1 (17.0 vs. 10.5 or 6.5, P < 0.001) and higher in children with severe (<10 U/dL) than moderate VWD (10-30 U/dL) (11.0 vs. 7.0, P < 0.001). Frequency of any bleeding, epistaxis, and oral cavity was higher in types 2 and 3 than in Type 1 VWD and was associated with VWF levels. We conclude that pediatric-specific bleeding symptoms occurred in a large proportion of children with moderate or severe VWD and should be included when evaluating children for VWD.

High VWF:Act and accumulation of FVIII were observed after perioperative FVIII-based replacement therapy in patients with VWD, both underlining the necessity of personalization of dosing regimens to optimize perioperative treatment.

It is unclear whether there are differences between von Willebrand factor (VWF) activity assays. We compared the four most used VWF activity assays in 661 von Willebrand disease (VWD) patients. All assays correlated excellently, but a discrepant classification was seen in 20% of patients. Differences between VWF activity assays have a large impact on the classification of VWD. Summary BackgroundMeasuring the ability of von Willebrand factor (VWF) to bind to platelets is crucial for the diagnosis and classification of von Willebrand disease (VWD). Several assays that measure this VWF activity using different principles are available, but the clinical relevance of different assay principles is unclear. ObjectiveTo compare the four most widely used VWF activity assays in a large VWD patient population. MethodsWe measured VWF:RCo (ristocetin to activate VWF + whole platelets), VWF:GPIbR (ristocetin + platelet glycoprotein Ib receptor [GPIb] fragments), VWF:GPIbM (gain‐of‐function GPIb fragments that bind VWF spontaneously without ristocetin) and VWF:Ab (monoclonal antibody directed against the GPIb binding epitope of VWF to mimic platelets) in 661 VWD patients from the nationwide ‘Willebrand in the Netherlands’ (WiN) Study. ResultsAll assays correlated excellently (Pearson r > 0.9), but discrepant results led to a different classification for up to one‐fifth of VWD patients. VWF:RCo was not sensitive enough to classify 18% of patients and misclassified half of genotypic 2B VWD patients, especially those with p.Arg1306Trp. VWF:GPIbR was more sensitive, accurately classified the vast majority of patients, and was unaffected by the p.Asp1472His variant that causes artificially low VWF:RCo. VWF:GPIbM was the most precise assay but misclassified over a quarter of genotypic 2A, 2B and 3 patients. VWF:Ab, often not considered an actual VWF activity assay, performed at least equally to the other assays with regard to accurate VWD classification. ConclusionAlthough the different VWF activity assays are often considered similar, differences between assays have a large impact on the classification of VWD.

Key Points• We identify rs41314453 as the strongest genetic predictor of ADAMTS13 activity, associated with a decrease of .20%.• We present evidence of further independent associations with a common variant in SUPT3H, as well as 5 variants at the ADAMTS13 locus.A disintegrin and metalloproteinase with thrombospondin motifs 13 (ADAMTS13) cleaves von Willebrand factor, reducing its prothrombotic activity. The genetic determinants of ADAMTS13 activity remain unclear. We performed a genome-wide association study of ADAMTS13 activity in the Rotterdam Study, a population-based cohort study. We used imputed genotypes of common variants in a discovery sample of 3443 individuals and replication sample of 2025 individuals. We examined rare exonic variant associations in ADAMTS13 in 1609 individuals using an exome array. rs41314453 in ADAMTS13 was associated with ADAMTS13 activity in both our discovery (b, 220.2%; P 5 1.3 3 10 233) and replication sample (P 5 3.3 3 10 234 ), and explained 3.6% to 6.5% of the variance. In the combined analysis of our discovery and replication samples, there were 2 further independent associations at the ADAMTS13 locus: rs3118667 (b, 3.0; P 5 9.6 3 10 221) and rs139911703 (b, 211.6; P 5 3.6 3 10 28). In addition, rs10456544 in SUPT3H was associated with a 4.2 increase in ADAMTS13 activity (P 5 1.13.6 3 10 28). Finally, we found 3 independent associations with rare coding variants in ADAMTS13: rs148312697 (b, 232.2%; P 5 3.7 3 10 26 ), rs142572218 (b, 246.0%; P 5 3.9 3 10 25 ), and rs36222275 (b, 213.9%; P 5 2.9 3 10 23 ). In conclusion, we identified rs41314453 as the main genetic determinant of ADAMTS13 activity, and we present preliminary findings for further associations at the ADAMTS13 and SUPT3H loci. (Blood. 2015;125(25):3949-3955)