Contribution of Select ISTH-BAT Subscores to the Total Score in Type 1 VWD

Background:

von Willebrand Disease (VWD) is the most common inherited bleeding disorder with partial quantitative deficiency in von Willebrand Factor (VWF); Type 1 comprises 80% of VWD. Clinical manifestations include mucocutaneous bleeding, prolonged bleeding after surgery or injury and excessive menorrhagia in females which have also been reported in normal subjects. A diagnosis of Type 1 VWD is based upon reduced plasma VWF, abnormal mucocutaneous bleeding symptoms and usually a family history of bleeding and VWD. Evaluating abnormal bleeding symptoms involves a detailed bleeding history, which can be quite subjective and time consuming. To address these challenges, the Vicenza-based Bleeding Assessment Tool (BAT) was developed as a validated score and has evolved into the current International Society on Thrombosis and Haemostasis-Bleeding Assessment Tool (ISTH-BAT). A large multi-center NIH supported study (The Zimmerman Program for the Molecular and Clinical Biology of VWD), began in 2005 to correlate clinical laboratory testing, bleeding severity determined by the ISTH-BAT and genetic variability in VWD. In this current study, we investigated which bleeding symptoms were most sensitive in applying the ISTH-BAT to the diagnosis of Type I VWD.

Methods:

Subjects were enrolled in the Zimmerman Program . Each symptom in the validated ISTH-BAT questionnaire was scored from 0-4 (no symptoms to symptom intervention) and included epistaxis, bruising, oral bleeding, hematuria, gastrointestinal (GI) bleeding, head bleeding, hemarthrosis, hematoma and prolonged bleeding with minor wounds, tooth extraction, surgery, menstruation and child birth. Other scored bleeding symptoms included bleeding at circumcision, excessive umbilical stump bleeding, venipuncture bleeding, vacuum extraction delivery bleeding, ovulatory bleeding and cephalohematoma. The scores of each symptom were analyzed in both healthy controls and subjects diagnosed with Type 1 VWD. Only subjects with VWF antigen (VWF:Ag) and/or VWF ristocetin cofactor activity (VWF:RCo) <30 IU/dL were considered in the comparative analysis. VWF levels were performed by a central laboratory, including VWF:Ag, VWF:RCo, VWF propeptide (VWFpp) and VWF collagen binding with type III collagen (VWF:CB). Statistical analysis included Mann-Whitney test, Chi-square or a Fisher's exact test, Pearson correlations and Spearman correlations. Results were considered significant for a two-sided p-value <0.05. A regression analysis was performed to examine which subscores contributed the most to the total score of the ISTH-BAT.

Results:

Analysis included 383 subjects (Female=262, Male=121) enrolled in the Zimmerman Program . Of these subjects, 244 were healthy controls (mean age of 38.93 [range 10-73 years of age]) and 139 had Type 1 VWD (mean age of 19.46 [range 1-76 years of age]). Within the Type 1 subjects, there were more females >12 years of age (no gender difference < 12 years of age) and greater number of Caucasians and younger subjects. Type 1 VWD subjects scored significantly higher than the healthy control group in both ISTH-BAT total scores (p<0.0001) as well as all subscores (p<0.001). In comparing bleeding symptoms from healthy controls with Type 1 VWD subjects: epistaxis 4% vs 46%, bruising 16% vs 64%, minor wound bleeding 1% vs 42%, oral bleeding 3% vs 35%, tooth extraction bleeding 3% vs 18%, GI bleeding 3% vs 11%, hematuria 0% vs 11%, surgical bleeding 4% vs 23%, menstrual bleeding 60% vs 85%, bleeding after delivery 2% vs 12%, other bleeding 0% vs 11% (47% were circumcision bleeding), head bleeding 0% vs 4%, hemarthrosis 0% vs 11%, and hematoma 0% vs 7%. Regression analysis revealed that epistaxis, bruising, excessive bleeding with minor wounds, oral bleeding, and menstrual bleeding subscores contributed the most to the ISTH-BAT total score (p<0.016).

Conclusion:

The ISTH-BAT currently is strongly predictive of bleeding symptoms in the diagnosis of Type 1 VWD. Though all ISTH-BAT subscores correlated with a diagnosis of Type 1 VWD, some subscores contributed more significantly to the total score than others and were more prevalent than in normal subjects. Accordingly, the sensitivity and specificity of ISTH-BAT subscores are critical to the assessment of bleeding in the diagnosis of Type 1 VWD.