Table 2

Incidence of SLE in PSM study group

	Before PSM (1:20 age–sex matching)		1:2 PSM
	Non-ITP n=14 460	ITP n=723	Non-ITP n=1336	ITP n=668
Follow-up person months	1 288 470	54 840	115 163	51 334
SLE	27	34	3	29
Incidence rate* (95% CI)	2.10 (1.44 to 3.06)	62.0 (44.3 to 86.8)	2.60 (0.84 to 8.08)	56.5 (39.3 to 81.3)
Crude relative risk (95% CI)	Reference	29.6 (17.9 to 49.0)	Reference	21.7 (6.61 to 71.2)

*Incidence rate, per 100 000 person-months.
ITP, idiopathic thrombocytopenic purpura; PSM, propensity score matching; SLE, systemic lupus erythematosus.