A systematic two-sample and bidirectional MR process highlights a unidirectional genetic causal effect of allergic diseases on COVID-19 infection/severity

Table 1 Overall MR analyses with strong genetic instruments (p < 5E−08) for the causal effects of various allergic diseases on COVID-19 infection/severity

Exposure	Outcome	No. of clumped SNPs^a	No. of SNPs in MRA^b	MR p-value^c	MR method^d	Heterogeneity	Pleiotropy	Directionality
BAD	A2	144	111	3.26E−02	IVW (random effects)	Yes	No	True
	B2		115	1.02E−01	IVW (random effects)	Yes	No	True
	C2		118	9.12E−01	IVW (random effects)	Yes	No	True
Asthma2020	A2	231	215	2.00E−04	IVW (random effects)	Yes	No	True
	B2		220	2.01E−02	IVW (random effects)	Yes	No	True
	C2		223	2.85E−01	IVW (random effects)	Yes	No	True
ADE2015	A2	20	19	5.11E−01	IVW (fixed effects)	No	No	True
	B2		19	7.98E−02	IVW (fixed effects)	No	No	True
	C2		20	2.64E−01	IVW (fixed effects)	No	No	True
PA	A2	5	3	2.29E−01	IVW (fixed effects)	No	No	True
	B2		3	1.66E−01	IVW (fixed effects)	No	No	True
	C2		4	2.66E−02	IVW (fixed effects)	No	No	True
SA	A2	19	10	6.73E−03	IVW (fixed effects)	No	No	True
	B2		10	1.61E−03	IVW (fixed effects)	No	No	True
	C2		11	2.43E−03	IVW (random effects)	Yes	No	True

^aNo. of clumped SNPs: number of independent genetic SNPs with a p-value < 5 × 10^–8 after clumping
^bNo. of SNPs in MRA: number of independent genetic SNPs used in the MR analysis for each pair of exposure and outcome
^cMR p-value: p-value of the most suitable MR method
^dMR method: the most suitable MR analysis used in MR analysis. Bold values indicate that the MR p-value is less than 0.05, while italic values indicate that the MR p-value is marginally significant

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