Is ABO blood group truly a risk factor for thrombosis and adverse outcomes?

Table 1 The incidence of ABO phenotypes in populations from different racial backgrounds

Race	Blood group phenotype	Blood group genotypes
	O1 (O2 rare)	A1	A2	B	A1B	A2B
Caucasian	44%	33%	10%	9%	3%	1%
Asian	43%	27%	Rare	25%	5%	Rare
African	49%	19%	8%	20%	3%	1%

Illustrations: Sub-group A2 expresses less A antigen on the red cell surface and has been referred to as “weak” A.

Table 2 The association of ABO genotype with von Willebrand factor and factor VIII levels is presented with categorization by von Willebrand factor levels

	Genotype	Median value
		vWF	FVIII
Low	O1O1	69%	75%
Medium	A1O, A2O, BO	89%	96%
High	AA, BB, A1B	120%	117%
Highest	A2B	169%	112%

vWF: Von Willebrand factor; FVIII: Factor VIII.

Table 3 Outline of the main studies describing the association of ABO blood type and manifestations of atherosclerotic heart disease

Ref.	Population	Sample size	Outcome(s)	Findings
Garrison et al[44]	United States		“Cardiovascular disease”	O showed the lowest incidence
Whincup et al[45]	United Kingdom (men only)	7662	CAD	Individuals with A blood type has higher incidence of CAD (RR = 1.21, CI: 1.01-1.46)
Rosenberg et al[46]	United States (young women)	225 MI vs 802 controls	MI	Blood group A was associated with MI
Lee et al[47]	Taiwan (young patients)	136 CAD vs 129 without CAD	CAD and MI	Group A was associated with increased risk of CAD (OR = 2.61, CI: 1.11-6.14) and MI (OR = 3.53, CI: 1.21-10.29)
Sari et al[48]	Turkish	476 MI vs 203 healthy control	MI	ABO blood type is not associated with development of MI
Carpeggiani et al[49]	Italy	4901	MI and CAD	Group non-O is associated with increased mortality in patients with CAD, groups A and B prevail in MI
Nydegger et al[50]		177 patients vs 89 control	MI	B allele carriers had higher MI (OR = 2.7, CI: 1.1-6.8)
Stakisaitis et al[51]	Lithuania	441	CAD	B blood group can be related with CAD in women
Meade et al[52]	United Kingdom	1393 men with 178 IHDs	CAD and MI	Incidence was significantly higher in blood group AB
Mitchell et al[53]	United Kingdom		“Cardiovascular disease”	Towns with higher prevalence of group O have higher rate of cardiovascular mortality
Biswas et al[54]	India	250 CAD vs 250 controls	CAD	Group O increases the risk of CAD
Amirzadegan et al[55]	Iran	2016 patients	CAD	No correlation
Biancari et al[56]	Finland	1152 CABG patients	MI	No correlation
He et al[57]	United States	89501	Coronary heart disease	AB group has highest CAD risk, followed by groups B, A and O

CAD: Coronary artery disease; MI: Myocardial infarction.