Data on lupus anticoagulant (LA) test stability in patients persistently positive for LA are limited, and its implications on clinical outcomes are lacking. We investigated the rate and predictors of a negative LA test and whether experiencing a negative test affected a patient's risk of future thrombotic events or death in a prospective observational study of persistently LA+ patients. We followed 164 patients (84% women) for a median of 9.2 years and a total of 1438 follow-up visits. During the observation period, 50 thrombotic events (23 arterial and 27 venous events) occurred, and 24 patients died. Forty-six of the patients had at least 1 negative LA test during the observation period, corresponding to a 10-year cumulative incidence of a negative LA test of 28% (95% confidence interval, 20-35). The majority of patients with available follow-up after a negative LA test (n = 41) had at least 1 subsequent positive test for LA (n = 28/41, 68%). Vitamin K antagonist (VKA) treatment at baseline was associated with a negative LA test during follow-up. Using a multistate time-to-event model with multivariable adjustment, a negative LA test had no impact on a patient's prospective risk of thrombosis or mortality. We conclude that a negative LA test during observation cannot be used clinically to stratify a patient's risk for future events.
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