The process of determining which actual pattern is on hand is called 辩证 ( biàn zhèng, usually translated as “pattern diagnosis”, “pattern identification” or “pattern discrimination”). Generally, the first and most important step in pattern diagnosis is an evaluation of the present signs and symptoms on the basis of the “Eight Principles” (八纲, pinyin: bā gāng). These eight principles refer to four pairs of fundamental qualities of a disease: exterior/interior, heat/cold, vacuity/repletion, and yin/yang. Out of these, heat/cold and vacuity/repletion have the biggest clinical importance. The yin/yang quality, on the other side, has the smallest importance and is somewhat seen aside from the other three pairs, since it merely presents a general and vague conclusion regarding what other qualities are found. In detail, the Eight Principles refer to the following:
- Yin and yang are universal aspects all things can be classified under, this includes diseases in general as well as the Eight Principles’ first three couples. For example, cold is identified to be a yin aspect, while heat is attributed to yang. Since descriptions of patterns in terms of yin and yang lack complexity and clinical practicality, though, patterns are usually not labelled this way anymore. Exceptions are vacuity-cold and repletion-heat patterns, who are sometimes referred to as “yin patterns” and “yang patterns” respectively.
- Exterior (表, pinyin: biǎo) refers to a disease manifesting in the superficial layers of the body – skin, hair, flesh, and meridians. It is characterized by aversion to cold and/or wind, headache, muscle ache, mild fever, a “floating” pulse, and a normal tongue appearance.
- Interior (里, pinyin: lǐ) refers to disease manifestation in the zàng-fǔ, or (in a wider sense) to any disease that can not be counted as exterior. There are no generalized characteristic symptoms of interior patterns, since they’ll be determined by the affected zàng or fǔ entity.
- Cold (寒, pinyin: hán) is generally characterized by aversion to cold, absence of thirst, and a white tongue fur. More detailed characterization depends on whether cold is coupled with vacuity or repletion.
- Heat (热, pinyin: rè) is characterized by absence of aversion to cold, a red and painful throat, a dry tongue fur and a rapid and floating pulse, if it falls together with an exterior pattern. In all other cases, symptoms depend on whether heat is coupled with vacuity or repletion.
- Deficiency (虚, pinyin: xū), can be further differentiated into deficiency of qi, xuě, yin and yang, with all their respective characteristic symptoms. Yin deficiency can also cause “empty-heat”.
- Excess (实, pinyin: shí) generally refers to any disease that can’t be identified as a deficient pattern, and usually indicates the presence of one of the Six Excesses, or a pattern of stagnation (of qi, xuě, etc.). In a concurrent exterior pattern, excess is characterized by the absence of sweating.