Table 4.

Rates of thromboses in subgroups defined by different assessments of persistently positive lupus anticoagulant

Patient group	Events	Person-years	Rate per 100 person-years	Rate ratio	P value	Adjusted rate ratio*	P value
Persistent positivity based on the first two lupus anticoagulant assessments
No	81	5178	1.5	1.00 (ref)		1.00 (ref)
Yes	10	232	4.3	2.75 (1.40 to 5.41)	0.0034	3.42 (1.76 to 6.65)	0.0003
Persistent positivity based on annual assessments
No	76	5059	1.5	1.00 (ref)		1.00 (ref)
Yes	15	352	4.2	2.75 (1.60 to 4.73)	0.0003	3.08 (1.83 to 5.19)	<0.0001
Persistent positivity based on the first 16 lupus anticoagulant assessments
No	70	4851	1.4	1.00 (ref)		1.00 (ref)
Yes	21	560	3.8	2.62 (1.60 to 4.28)	0.0001	2.75 (1.71 to 4.42)	<0.0001
Proportion of the first 16 assessments positive for lupus anticoagulant
None	61	4338	1.4	1.00 (ref)		1.00 (ref)
1%–49%	18	823	2.2	1.60 (0.90 to 2.86)	0.11	1.51 (0.84 to 2.72)	0.17
50%+	12	250	4.8	3.42 (1.88 to 6.23)	<0.0001	3.86 (2.17 to 6.87)	<0.0001
Mean value of dRVVT in the first 16 assessments
<35 s	31	2555	1.2	1.00 (ref)		1.00 (ref)
35–45 s	43	2503	1.7	1.40 (0.86 to 2.27)	0.18	1.33 (0.82 to 2.16)	0.25
45+ s	17	352	4.8	3.96 (2.25 to 6.99)	<0.0001	4.14 (2.36 to 7.27)	<0.0001

*Adjusted for age, race and sex.

dRVVT, dilute Russell viper venom time; ref, reference group.