Table 1.

Estimated Incidence of Potential Thrombotic APS and Obstetric APS Events in the USA

Potential APS Event	Annual Event Incidence in the USA per 100 000 Person-Years	Percentage of Events Attributed to APS	Incidence of Event Attributable to APS in General Population per 100 000 person-years	References
Venous thromboembolism	120 (total)	6%	All events 2.9-7.2	(4, 8, 15-18)
	7 (first VTE, unprovoked, <50 years old)	14%
	37 (first VTE, unprovoked, >50 years old)	5%
	44 (first VTE, unprovoked, all ages)	9%
Myocardial infarction	15 (<45 years old)	4.5%-8%	0.7-1.2	(1, 4, 9, 23, 24)
Stroke	15 (<50 years old)	11%-16%	1.7-2.4	(1, 9, 19, 20, 23, 24)
Early pregnancy loss	13	8.5%-11.5%	1.1-1.5	(10-12, 23, 24)
Late pregnancy loss	7	4%-8%	0.3-0.6	(13, 21, 23)
Pre-term delivery due to preeclampsia	4	10%-20%	0.4-0.8	(14, 22)

APS, antiphospholipid syndrome; VTE, venous thromboembolism.