Background Antiphospholipid syndrome (APS) is a rare and complicated acquired autoimmune thrombophilia characterized by arterial/venous thrombosis and/or recurrent pregnancy loss. Thrombosis is the first cause of death of APS patients. However, there has been no generally acknowledged model to predict thrombosis. Only adjusted global APS score (aGAPSS) was developed for prediction but based on a cross-sectional study¹. Additionally, the predictive ability of Padua score and Caprini score has not been validated in APS patients.

Objectives Aim to validate the ability of aGAPSS, Padua score and Caprini score to predict thrombosis in APS patients basing on a prospective cohort.

Methods Consecutive APS patients who fulfilled the 2006 Sydney Revised Classification Criteria for APS, referred to Peking Union Medical College Hospital were included. Clinical data, aGAPSS, Padua score, and Caprini score at the time of diagnosis were collected. Patients with less than 1-year follow-up were excluded. Harrell c-index and calibration curve were used to validate the prediction models.

Results A total of 302 patients were enrolled in this study. The mean age was 32±12 years old, and 202 (66.9%) were female (Table 1). Patients were followed up for a median of 36 months. During the follow-up period, there were 62 thrombotic events, with 40 (13.25%) venous and 22 (7.28%) arterial thrombosis. The 1-, 3-, and 5-year thrombosis risks were 8.9%, 16.9%, and 21.3% respectively (Figure 1A). The Harrell c-indexes for predicting thrombosis of aGAPSS, Padua score, and Caprini score were 0.56 (95% confidence interval [CI], 0.52-0.60), 0.58 (95% CI, 0.54-0.62), and 0.61 (95%CI, 0.57-0.65) respectively. The model predicting venous thrombosis with the best discrimination was Padua score whose Harrell c-index was 0.64 (95% CI, 0.60-0.68), and the model predicting arterial thrombosis with the best discrimination was Caprini score whose Harrell c-index was 0.62 (95%CI, 0.56-0.68). The calibration curves illustrated that the calibration for predicting thrombosis within 3 years after diagnosis of all the 3 models was poor (Figure 1B-D).

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Figure 1.

The Kaplan-Meier curve and the calibration curve of 3 prediction models within 3 years after diagnosis. A: The Kaplan-Meier curve of venous, arterial and both venous and arterial thrombosis. B: The calibration curves for venous thrombosis. C: The calibration curves for arterial thrombosis. D: The calibration curves for both venous and arterial thrombosis.

Conclusion The ability of aGAPSS, Padua score and Caprini score to predict thrombosis in APS patients is relatively poor. Construction of a new prediction model specifically for APS patients is required to help with early prevention and treatment.

References [1]Sciascia, S., et al., GAPSS: the Global Anti-Phospholipid Syndrome Score. Rheumatology (Oxford), 2013. 52(8): p. 1397-403.

Disclosure of Interests None declared