Serological evolution in patients with positive antiphospholipid antibodies: a retrospective study of Chinese cohort

Lanlan JI; Zhuoli ZHANG

ABSTRACT

Objective:

To explore the clinical and serological evolution of patients with positive antiphospholipid antibodies (aPL), and the factors and therapeutic implications associated with aPL negativization.

Methods:

Patients with a persistent serological positive aPL according to established criteria between 1997 and 2018 were included. The Lupus anticoagulant (LA), anti-cardiolipid antibody (aCL) and anti-β 2 glycoproteinⅠ (anti-β 2GPⅠ) were tested following the International Society on Thrombosis and Haemostasis guidelines. The patients were classified as aPL negativization if the following aPL tests became negative, on two or more occasions at least 12 weeks apart. Titer more than 40 RU/ml was defined as moderate to high titer for anti-aCL and anti-β 2GPⅠ. For patients receiving warfarin, the results of LA were counted only when international normalized ratio (INR)<1.5.

Results:

There were 93 patients finally involved. 25% of them were primary APS and 63% were conco-mitant with systemic lupus erythematosus (SLE). After a mean follow-up of 45.0 (45.0) months, the percentage of aPL negativization was 11%(9/83), 26%(18/69), 24%(13/53) for LA, aCL and anti-β 2GP Ⅰ respectively. Multivariate analysis confirmed that double positive of dilute russell's viper venom time (dRVVT) and silica clotting time (SCT) was the only independent protective factor for LA negativization [ OR=0.055, 95% CI (0.006, 0.545); P=0.013]. SLE, moderate to high titer of aCL and number of baseline aPL positivity were independently associated with aCL negativization [ OR=18.2; 95% CI (1.45, 228); P=0.025, for SLE; OR=0.217; 95% CI (0.053, 0.888); P=0.034, for moderate to high titer of aCL; OR=0.198; 95% CI(0.057, 0.689); P=0.011, for number of baseline aPL positivity]. Moderate to high titer of anti-β 2GPⅠ and number of baseline aPL positivity were independent protective factors for anti-β 2GPⅠnegativization [ OR=0.168; 95% CI (0.032, 0.872); P=0.034, for moderate to high titer of anti-β 2GPⅠ; OR=0.243; 95% CI (0.073, 0.813); P=0.022, for number of baseline aPL positivity]. There were no factors related with aPL negativization among 40 triple aPL positive patients. We didn't find any relationship between aPL persistent positivity and further thrombosis/pregnancy morbidity due to limited events.

Conclusion:

aPLs negativization is common and frequent for aCL. The number of positive antibodies and higher antibody load are associated with persistently positive serology. Patients with SLE are easier to get aCL negativization. Double positive of dRVVT and SCT was a protective factor for LA negativization.