The purpose of this study was to investigate whether visible and near-infrared (Vis-NIR) spectroscopy can be used for diagnoses of anti-phospholipid syndrome (APS). Vis-NIR spectra from 90 plasma samples [anti-phospholipid antibodies (aPLs)-positive group, n = 48; aPLs-negative group, n = 42] were subjected to principal component analysis (PCA) and soft independent modeling of class analogy (SINICA) to develop multivariate models to discriminate between aPLs-positive and aPLs-negative. Both PCA and SINICA models were further assessed by the prediction of 84 masked other determinations. The PCA model predicted successful discrimination of the masked samples with respect to aPLs-positive and aPLs-negative. The SINICA model predicted 42 of 48 (87.5%) aPLs-positive patients and 33 of 36 (91.7%) aPLs-negative patients of Vis-NIR spectra from masked samples correctly. These results suggest that Vis-NIR spectroscopy combined with multivariate analysis could provide a promising tool to objectively diagnose APS. (c) 2007 Elsevier Inc. All rights reserved.