Bianzheng (pattern identification) is the core diagnostic methodology in traditional Chinese medicine (TCM). It emphasises a holistic analysis of the patient’s symptoms, signs, and overall condition in order to discern the nature of the disorder and its pathomechanism. Distinct from bianbing (disease differentiation) in Western medicine, which centres on disease entities and nosological labels, pattern identification does not focus primarily on the name of a disease but on the concrete manifestations of imbalance of yin and yang and disharmony of qi and blood, thereby guiding the formulation of individualised therapeutic strategies.

The theoretical foundation of pattern identification can be traced back to the Huangdi Neijing (Yellow Emperor’s Inner Canon), in which the essential methodology lies in sizhen hecan (combination of the four diagnostic methods), namely wang (inspection), wen (auscultation and olfaction), wen (inquiry), qie (palpation), to comprehensively gather clinical information. On this basis, the clinician analyses location, nature, progression, and the relationship between pathogenic qi and healthy qi. The representative framework of bagang bianzheng (pattern identification by the eight principles) classifies patterns into eight fundamental categories: yin, yang, exterior, interior, cold, heat, deficiency, and excess. For example, what Western medicine broadly terms an “upper respiratory tract infection” may, in TCM, be differentiated into patterns such as fenghan (wind‑cold), fengre (wind‑heat), shushi (summerheat‑dampness), or qixu (qi deficiency). Accordingly, treatment varies: Mahuang Tang (Ephedra Decoction) is used to release the exterior and disperse wind‑cold, whereas Yinqiao San (Lonicera and Forsythia Powder) is prescribed to disperse wind and clear heat. This fully embodies the principle of tongbing yizhi (different treatments for the same disease), a hallmark of bianzheng lunzhi (treatment based on pattern identification), in which therapeutic methods are determined according to the differentiated pattern rather than the disease label.

Beyond bagang bianzheng (pattern identification by the eight principles), other principal frameworks include liujing bianzheng (pattern identification of six meridians), particularly applied to externally contracted disorders; zang-fu bianzheng (pattern identification according to viscera and bowels), which analyses internal pathomechanisms; and qixue jinye bianzheng (pattern identification according to qi, blood and body fluids), which focuses on the movement and transformation of vital substances within the body’s functional network. Ming Dynasty physician Zhang Jingyue stated in Jingyue Quanshu (Complete Works of Jingyue): “In all diagnosis, one must first examine yin and yang”, underscoring the primacy of determining the fundamental yin-yang nature of a disorder. Subsequently, Ye Tianshi of the Qing Dynasty developed weiqi yingxue bianzheng (pattern identification according to defence, qi, nutrient and blood), thereby deepening understanding of the transmission and progression of warm diseases and illustrating the dynamic and integrative character of pattern differentiation systems.

The most distinctive features of bianzheng (pattern identification) lie in its holistic orientation and individualised application. Attention is given not only to presenting symptoms but also to constitutional endowment, environmental influences, and emotional factors. Zhu Zhenheng of the Yuan Dynasty proposed the constitutional view that “yang is often in excess, while yin is often insufficient”, highlighting the necessity of adapting treatment to individual characteristics. In Shanghan Lun (Treatise on Cold Damage), Zhang Zhongjing articulated the principle: “Observe the mai (vessel) and zheng (pattern), discern the pathological deviation, and treat according to the pattern”, concisely expressing the flexibility and responsiveness that define treatment based on pattern identification in TCM.