Abstract Number: PB1561
Meeting: ISTH 2020 Congress
Theme: Platelet Disorders and von Willebrand Disease » VWF and von Willebrand Factor Disorders - Clinical Conditions
Background: The term low von Willebrand factor (VWF) is referred to patients with VWF levels of 30-50 IU/dL. Diagnosis and management of patients with low VWF levels is clinically challenging.
Aims: To determine the clinical and phenotypic features of patients with low VWF.
Methods: We evaluated 29 patients with low VWF levels (VWF:Ag and/or VWF:RCo in the range of 30-50 IU/dL) and compared them with 36 VWD patients and 25 healthy control. All subjects underwent a panel of VWF tests, including VWF activity (VWF:RCo and VWF:CB), VWF:Ag, FVIII:C, RIPA and blood group typing. The ISTH Bleeding Assessment Tool (BAT) was assessed for each subject and was considered abnormal if BS was >3 for males or >5 for females.
Results: Demographic characteristics of the study population are summarized in Table 1. In patients with low VWF the mean of VWF:Ag was 47 IU/dL and VWF:RCo was 33 IU/dL and were significantly lower than control (114 IU/dL; P < .0001 and 116 IU/dL; P < .0001 respectively). In comparison to healthy control the median of BS in patients with low VWF was significantly higher (6.5 vs. 1.96; P < .0001) but was not significantly different from VWD patients (Table 2). 73% of female patients with low VWF had the experience of menorrhagia. Albeit significant bleeding in low VWF patients and reduced FVIII:C levels compared with controls (mean 65 IU/dL vs. 114 IU/dL; P < .0002), FVIII:C were normal in 83% of our low VWF cohort. FVIII:C/VWF:Ag ratios were significantly increased in low VWF levels patients as well as VWD patients compared with controls (P < .0002) that represent decreased VWF synthesis and/or secretion.
Conclusions: Our findings showed that low VWF levels can be associated with significant bleeding and patients should be considered as having a mild bleeding disorder rather than having a risk factor for bleeding.
| Subjects | N | Median age years | Blood group (O/non-O) | Gender (male/female) |
| Healthy control | 25 | 35(24-59) | 9/16 | 13/12 |
| Low VWF | 29 | 27(1-54) | 16/13 | 10/19 |
| VWD | 36 | 20(5-62) | 10/12 | 17/19 |
[Table 1 characteristics of the study population]
| Variable | Low VWF (n: 29) | VWD (n:36) | Healthy control (n:25) |
| FVIII:C (IU/dl) | 64(55-120) | 42(8-78) | 114(66-158) |
| VWF:Ag (IU/dl) | 48(39-110) | 32(2-70) | 116(70-196) |
| VWF:RCo (IU/dl) | 34(30-38) | 14(1-36) | 81(55-135) |
| VWF:CB (IU/dl) | 49(30-120) | 19(2-76) | 92(57-133) |
| FVIII:C/VWF:Ag | 1.3 (0.86-1.95) | 1.3(0.25-5.56) | 0.97(0.65-1.2) |
| Bleeding Score | 6.5(1-20) | 7.5(1-21) | 1.96(0-6) |
[Table 2 Median (range) of laboratory results]
To cite this abstract in AMA style:
Seidi Zadeh O, Ahmadinejad M, Mojtabavi M, Homayoun S. Clinical and Phenotypic Evaluation of Patients with Low von Willebrand Factor [abstract]. Res Pract Thromb Haemost. 2020; 4 (Suppl 1). https://abstracts.isth.org/abstract/clinical-and-phenotypic-evaluation-of-patients-with-low-von-willebrand-factor/. Accessed September 24, 2023.« Back to ISTH 2020 Congress
ISTH Congress Abstracts - https://abstracts.isth.org/abstract/clinical-and-phenotypic-evaluation-of-patients-with-low-von-willebrand-factor/