An independent validation of the Global Anti-Phospholipid Syndrome Score in a Japanese cohort of patients with autoimmune diseases

Sir, We previously proposed a quantitative score defined as ‘antiphospholipid score (aPL-S)’, in which, by testing multiple antiphospholipid antibodies (aPL), thrombotic risk may be evaluated in antiphospholipid syndrome (APS) patients. This score is validated in our cohort, as well as cohorts in other institution, as a useful quantitative index for diagnosing APS and predicting thrombosis in autoimmune diseases. Recently, Sciascia et al. broadened this idea by taking into account the aPL profile with conventional cardiovascular risks, and developed and validated the ‘Global Anti-Phospholipid Syndrome Score’ (GAPSS) as a marker of APS manifestations. In order to validate the GAPSS independently, we applied it to a cohort of 282 consecutive patients who attended the Hokkaido University Hospital rheumatology clinic from January 2002 to December 2003. There were 41 APS (17 primary APS) patients, 88 systemic lupus erythematosus (SLE) without APS, 50 rheumatoid arthritis, 16 Sjogren’s syndrome, 21 systemic sclerosis, 10 polymyositis/dermatomyositis and 56 other autoimmune diseases. Overall, thrombosis and/or pregnancy loss (APS manifestations) were observed in 43 patients (38 arterial thrombosis, 24 venous thrombosis and 11 pregnancy loss). Higher values of GAPSS were observed in patients who had experienced one or more of the APS manifestations compared with the patients without APS manifestations (Figure 1). When clinical subgroups were analyzed, patients with a history of arterial and/or venous thrombosis showed higher GAPSS compared with patients without APS manifestations. Patients with a history of pregnancy morbidity failed to show a significant difference in GAPSS compared with patients without APS manifestations (Figure 1). The smaller number of patients with history of pregnancy loss in our cohort was likely to be a primary factor in the insignificance of GAPSS in evaluating risks of pregnancy loss. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), positive likelihood ratio (PLR), negative likelihood ratio (NLR), and area under the curve (AUC) of the receiver operating characteristic (ROC) curve at various levels of GAPSS cut-off are shown in Table 1. In our cohort, maximum AUC of ROC curve was at the cut-off level of GAPSS 6, lower than the cut-off level of GAPSS 10 in the original cohort in the UK. The reason for differences in adequate cut-off levels of ROC curve in GAPSS between two cohorts may be attributed to their different characteristic backgrounds. Our cohort consists of patients with various autoimmune diseases, while the original UK cohort comprised patients with APS and/or SLE. In our cohort, non-APS patients who scored GAPSS> 10 were all SLE patients (6/282). The high GAPSS in SLE patients was mainly due to the high incidence of ‘aPL carriers’. The adequate cut-off value of GAPSS may differ among patients with and without SLE. We demonstrated that aPL profile with conventional cardiovascular risks can be successfully quantified by GAPSS in an independent cohort of patients with autoimmune diseases. GAPSS correlated with a history of APS manifestations, particularly with thrombosis, suggesting that it is a suitable quantitative marker for APS. However, one should consider the appropriate cut-off to be adapted to different kinds of cohorts by reviewing their basic characteristics.