Table 21.

—[Section 7.1] Summary of Findings: Should Aspirin vs No Treatment Be Used for Prevention of VTE in Persons With Asymptomatic Thrombophilia?^157-160

Outcome	No. of Patients (Studies) Follow-up	Quality of the Evidence (GRADE)	Relative Effect (95% CI)	Anticipated Absolute Effects
				Baseline Risk	Risk Difference With Aspirin (95% CI)
Symptomatic nonfatal DVT and PE	98 (2 RCTs) 2.3-10.1 y	Low due to very serious imprecisiona	RR, 2.08 (0.20-22.23)	20 per 1,000	22 more per 1,000 (from 16 fewer to 425 more)
Mortality	98 (1 RCT) 2.3 y	Very low due to very serious imprecisiona and methodologic limitationsb	RR, 1.04 (0.07-16.19)	21 per 1,000	1 more per 1,000 (from 19 fewer to 316 more)
Major bleeding	207 (3 Observational studies) 2.3-8 y	Very low due to very serious imprecisiona	Not estimable, no events in either arm	0 per 1,000	Not estimable

See Table 1 and 4 legends for expansion of abbreviations.

^aVery small number of events.

^bErkan et al¹⁵⁹ terminated early as event rates were lower than expected and larger sample size was infeasible.