Background/Purpose: Past studies, mostly cross-sectional, have found a reduction in thrombosis in systemic lupus erythematosus (SLE) patients taking hydroxychloroquine (HCQ). We examined the relationship between hydroxychloroquine and other medications with thrombosis in a large prospective SLE cohort.

Methods: We studied 1795 SLE patients (56% Caucasian, 37% African American, 93.3% female, mean age 37.0 ±12.5) with no previous thrombosis prior to entry in the cohort. The primary outcome was first thrombotic event (arterial or venous). Univariate analysis and multivariable modeling were used to examine associations between prednisone, hydroxycholoquine, and NSAID use with the risk of thrombosis.

Results:

A total of 193 thrombotic events were observed over 10,508 person-years of follow-up (rate 18.4/1000 person-years). In the multivariable model controlling for age, traditional cardiovascular risk factors, and SLE disease activity, significant predictors for thrombosis included current prednisone dose (>20 mg/day, HR 4.4, p<0.0001) and Aspirin use (HR 1.8, p=0.0026). Hydroxychloroquine use remained protective for thrombosis (HR 0.6, p=0.0075). Subgroup analysis revealed that the protective effect of hydroxychloroquine was stronger in antiphospholipid antibody positive patients (HR 0.6, p=0.0090) than among antiphospholipid antibody negative patients (HR 0.8, p=0.57).

	Subgroup	Thrombotic events	Rate of events/ 1000 person-yrs	Rate Ratios (95% CI)	P-value
Current Prednisone	None	52	10.6	1.0 (Ref. Gp)
	1-9 mg/d	40	16.4	1.6 (1.1-2.4)	0.025
	10-19 mg/d	49	34.3	3.3 (2.2-4.8)	<0.0001
	20+ mg/d	43	71.8	6.5(4.3-9.8)	<0.0001
Cummulative Prednisone dose	None	29	13.1	1.0 (Ref. Gp)
	<1 yr (10 mg/d)	37	23.8	1.6 (1.0-2.6)	0.075
	1-3 yrs (10 mg/d)	30	19.0	1.8 (1.1-3.1)	0.026
	3-10 yrs (10 mg/d)	45	25.5	3.0 (1.8-5.2)	<0.0001
	>10 yrs (10 mg/d)	9	24.3	3.7 (1.5-9.4)	0.0056
Current HCQ	No	95	29.0	1.0 (Ref. Gp)
	Yes	90	14.6	0.5 (0.4-0.7)	<0.0001
HCQ use	Never	57	32.2	1.0 (Ref. Gp)
	Past (not current)	27	27.6	0.9 (0.6-1.5)	0.81
	<6 consecutive mo	16	20.0	0.6 (0.3-1.0)	0.056
	>6 consecutive mo	64	13.8	0.5 (0.3-0.7)	0.0003
NSAID use	No	146	21.6	1.0 (Ref. Gp)
	Yes	37	13.9	0.6 (0.4-0.9)	0.017
Aspirin use	No	137	17.9	1.0 (Ref. Gp)
	Yes	49	28.0	1.6 (1.2-2.3)	0.0038

Conclusion: Current prednisone dose was found to be a significant independant predictor of thrombosis in SLE, after adjustment for disease activity. Current hydroxychloroquine use decreased the risk of thrombosis in this prospective cohort, particularly in those with positive antiphospholipid antibodies. Aspirin use was not protective, likely due to the bias of indication.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/hydroxychloroquine-reduces-thrombosis-in-systemic-lupus-erythematosus-particularly-in-antiphospholipid-positive-patients/