Sir,
The ABO blood group type has a potential influence on hemostasis due to its effect on von Willebrand factor (VWF) and thereby on factor VIII plasma levels. ABO blood group genotyping has shown that O1O1 subjects have the lowest VWF levels, and non-O group individuals heterozygous for the O1 allele have significantly lower VWF levels than AA, AB, or BB subjects [1]. Studies on the effect of ABO blood group on the plasma levels of VWF have been carried out in different ethnicities [2, 3] but there is paucity of information in this regard from India. The aim of this study was to determine the influence of ABO blood group on plasma VWF:Ag level in normal South Indian population.
This was a cross-sectional analytical study over a 3-year period (May 2015 to May 2018) conducted in the Departments of Pathology and Transfusion Medicine in a tertiary care hospital in Southern India. Three hundred ninety four fit and healthy apheresis donors selected as per statutory drugs and cosmetic rules, and other Govt. of India guidelines were enrolled. After informed consent, blood was collected from each subject; 2 ml in EDTA for blood counts and forward ABO blood grouping and Rh typing (cell grouping); 3 ml in plain vial for the confirmation of ABO blood group by serum (reverse) grouping, antibody and transfusion transmitted infection screen; and additional 2 ml in citrate for the estimation of VWF:Ag. Standard tube technique was done using Anti- A, Anti-B, Anti- H and Anti-D monoclonal antisera (Tulip Diagnostics, India). For reverse blood grouping freshly prepared 5% known A, B, O blood group pooled red cells were used. The samples for the determination of VWF:Ag were centrifuged at 1500 g for 15 min and plasma was stored at -40˚C until assayed. The maximum duration of sample storage was 6–8 months. Estimation of VWF:Ag was carried out in batches using Enzyme Linked Immunosorbent Assay (ELISA). The kits (Raybiotech Life, Georgia, United States) were stored as per the manufacturer’s recommendation. Lyophilized standards supplied with kit were used for making the standard curve. The unit of plasma VWF:Ag level as per the kit insert was ng/ml. One way analysis of variance (ANOVA) was used to compare the mean VWF:Ag levels between the various ABO blood group phenotypes.
The age of donors ranged from 18–55 years with mean of 27.4 ± 7.4 years and all were male. The distribution of ABO blood groups was 18% (71) A, 43.7% (172) B, 35.8% (141) O and 2.5% (10) AB and the distribution of Rh D positive and negative phenotypes was 98% (386) and 2% (8) respectively. The split up of the blood groups and mean VWF:Ag level is given in Table 1. The mean VWF:Ag level among A, B, O and AB groups was 87.8 ± 20.5, 88.9 ± 15.3, 49.3 ± 12.4 and 91.7 ± 12.1 ng/ml respectively and among the RhD positive and negative group was 80.4 ± 16.9 and 74.6 ± 24.4 ng/ml. The overall mean VWF:Ag level was 74.6 ± 24.5 ng/ml. VWF:Ag level was significantly lower for O group than non-O group individuals (p < 0.001, F = 71.707).
Table1.
Distribution of blood groups among voluntary apheresis donors and their plasma VWF: Ag levels
| Blood group (Mean ± SD) | Total No. of donors | VWF: Ag levels ng/ml |
|---|---|---|
| A1 Positive | 65 | 86.7 ± 20.7 |
| A2 Positive | 2 | 122.4 ± 1.1 |
| A Negative | 4 | 87.5 ± 9.0 |
| Overall A group | 71 (18%) | 87.8 ± 20.5 |
| B Positive | 170 | 88.9 ± 15.4 |
| B Negative | 2 | 92.8 ± 0.7 |
| Overall B group | 172 (43.7%) | 88.9 ± 15.3 |
| O Positive | 139 | 49.2 ± 12.5 |
| O Negative | 2 | 53.7 ± 2.51 |
| Overall O group | 141(35.8%) | 49.3 ± 12.4 |
| A1B Positive | 8 | 92.1 ± 13.4 |
| A2B Positive | 2 | 89.2 ± 0.42 |
| Overall AB group | 10 (2.5%) | 91.7 ± 12.1 |
The lower VWF: Ag levels in O group individuals has been attributed to a shorter VWF survival [4] and increased susceptibility of VWF of blood group O, A, B and AB to proteolysis by the ADAMTS13 metalloprotease in the rank order O ≥ B ≥ A ≥ AB [5]. In conclusion, this study confirmed that VWF:Ag level is significantly lower in blood group O than in non-O group individuals in conjunction with earlier studies [1–3]. Hence, while interpreting VWF:Ag results, ABO blood group phenotype should be taken into notice to prevent overdiagnosis of von Willebrand Disease in blood group O or under diagnosis in non-O group patients.
Authors Contribution
PLA performed the bench work and prepared the manuscript; RK conceptualized the study, analyzed the results and edited the manuscript; DB and RGK provided support for the bench work and reviewed the manuscript.
Preliminary data from the study was presented as a poster in the ISTH 2017 Congress in Berlin.
Funding
This study was funded by JIPMER Intramural Grant for Faculty project.
Compliance with Ethical standards
Conflict of interest
Authors declare that they have no conflict of interest.
Ethical Standards
This study was conducted on blood samples received from fit and healthy apheresis donors selected as per statutory criteria. All were in accordance with the ethical standards of the institutional ethical committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
Ethical Approval
This study was approved by the Institute Ethics Committee.
Informed Consent
Informed written consent was obtained from the apheresis donors enrolled in the study according to Institute ethics guidelines.
Footnotes
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References
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