S100A8 showed good diagnostic accuracy for APS (area under the curve (AUC)=0.854, 95% CI 0.803 to 0.907, p<0.001), with similar performance for thrombotic APS (AUC=0.819, 95% CI 0.747 to 0.891, p<0.001) and obstetric APS (AUC=0.874, 95% CI 0.821 to 0.926, p<0.001). Here, S100A8 is linked to autoimmune polyendocrinopathy.