By the theory of Six Channels

This method first appeared in the Shang han lun (The Treatise on Febrile Diseases Caused by Exogenous Pathogenic Factors) by Zhang Zhongjing of the eastern Han Dynasty (25 B.C.-220 A.D.). In this book various clinical manifestations of febrile disease caused by exogenous pathogenic factors such as Taiyang syndromes, Yangming syndromes, Shaoyang syndromes, Taiyin syndromes, Shaoyin syndromes, and Jueyin syndromes are used to explain the location and nature of pathological changes, the strength and weakness of anti-pathogenic and pathogenic qi, and the tendency of disease development, as a guide for clinical treatment.

More about differentiating syndromes according to the Theories of the Six Channels.

By the theory of Four Stages of Wei, Qi, Ying, and Xue

This method was first put forward by Ye Tianshi, a Qing Dynasty (1644-1911 A.D.) physician, in his book "Wan Gan Wen Re Pain" (On Febrile Diseases Caused by Pathogenic Mild Heat). He classified the clinical manifestations of febrile diseases caused by pathogenic mild heat into four stage, wei (outer defensive) stage, qi (inner defensive) stage, yin (nutrient) stage, and xue (blood) stage. These are the four body strata used the explain the location and severity of pathological changes, and which form the basis of clinical treatment.

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By the Theory of Sanjiao

This was advocated by Wu Jutong, another Qing Dynasty physician. He summarized clinical manifestations of epidemic febrile diseases as having three areas: the upper, middle, and lower portions of the body cavity. These are also used to guide clinical treatment.

More about differentiating syndromes according to the Theories of Sanjiao.