The efficacy of traditional Chinese medicine (TCM) treatments for West medicine (WM) diseases relies heavily on the proper classification of patients into TCM syndrome types. The authors developed a data-driven method for solving the classification problem, where syndrome types were identified and quantified based on statistical patts detected in unlabeled symptom survey data. The new method is a generalization of latent class analysis (LCA), which has been widely applied in WM research to solve a similar problem, i.e., to identify subtypes of a patient population in the absence of a gold standard. A well-known weakness of LCA is that it makes an unrealistically strong independence assumption. The authors relaxed the assumption by first detecting symptom co-occurrence patts from survey data and used those statistical patts instead of the symptoms as features for LCA. This new method consists of six steps: data collection, symptom co-occurrence patt discovery, statistical patt interpretation, syndrome identification, syndrome type identification and syndrome type classification. A software package called Lant has been developed to support the application of the method. The method was ill ustrated using a data set on vascular mild cognitive impairment.