The procedure of the diagnosis and treatment for internal diseases include the following five steps: to recognice the disease based on the information obtained with the four diagnostic methods, to identify the location and nature of a disease, to infer the cause and judge the pathogenesis of a disease, to design the therapeutic principle and method, and to choose drugs and formulate a prescription.

  

The complete information about a disease can be collected by four diagnostic methods, i. e., inspection, olfaction and auscultation, interrogation and palpation. It includes the history and manifestations of the disease, and the influence of external environment on the onset and development of the disease. From the information collected, evidence will be provided for differentiating the syndromes, designing the therapeutic principle and organizing a prescription. Therefore the four diagnostic methods are an important procedure for collecting essential information about the disease and a prerequisite in syndrome differentiation.

Whether the information collected by applying the four diagnostic methods is accurate or not greatly influences the accuracy of syndrome differentiation. So the four diagnostic methods should be performed from different angles to avoid one-sided views and with prominence to the major aspects of the disease.

2. Identify the nature and location of a disease  

The fundamental pathogenesis of a disease is the conflict between pathogenic factors and anti-pathogenic qi, which will lead to the imbalance of yin and yang. The excess of yang will cause heat syndrome, while the excess of yin will lead to cold syndrome. For this reason, cold and heat indicate the nature of a disease. On the other hand, the conflict between pathogenic factors and antipathogenic qi will also be reflected as excess or deficiency. 

Therefore all syndromes can be classified into four categories, i.e., deficiency, excess, cold and heat. And the therapeutic principles such as replenishing deficiency, reducing excess, clearing away heat or warming cold should be applied accordingly. Identifying the nature of a disease is an important step in syndrome differentiation and helps draw an outline of a disease and enables a practitioner to design the general therapeutic principle for a disease.

    

The location of a disease means the depth, i.e., exterior and interior; or the site that a disease affects, i.e., zang-fu organs, qi and blood, or meridian. It is important to identify whether the exterior or interior is involved for the differentiation of exogenous diseases, while it is essential to identify whether the zang-fu organs, the meridians or qi and blood are involved for the differentiation of miscellaneous diseases. 

Miscellaneous diseases are usually classified into qifen disease and xuefen disease if they are located according to the conditions of qi and blood. Of all the methods for identifying the location of a disease, some are simple, and some are comprehensive. Each has a given scope of application, and may be used alone or together with others according to the clinical situations.

In order to refine the diagnosis and syndrome differentiation, it is necessary to infer the cause of the disease from the patient's complaints, the results obtained with the four diagnostic methods and the results of the laboratory tests, and from the time, the season, the environmental factors and climate when the disease develops as well, so as to make a synthetical analysis and find out where the crux lies. By so doing, the treatment principle can be decided with much ground.

The therapeutic principle and method are designed according to the result of syndrome differentiation. For example, the therapeutic principle of clearing away liver fire and lowering the adverse rising lung qi is designed for a cough categorized as syndrome of liver fire invading the lung. The therapeutic principle and method designed must be consistent with the pathogenesis of the disease.

Syndrome differentiation and therapeutic principle designed are the bases for formulating an appropriate prescription. Usually a traditional prescription is organized for a specific syndrome or disease. It is composed of drugs carefully selected in light of their compatibility and indicated for certain cases. To select an adequate prescription for a clinical case requires the knowledge about the ingredients, organizing principle, compatibility of the ingredients, indications and application of the prescription. 

Traditional prescriptions are the summary of clinical experience over thousands of years. They reflected the treatment strategy and philosophy created by practitioners from generation to generation for certain diseases under the guidance of TCM theory. And we are encouraged to study, apply and develop these prescriptions in clinical practice. In formulating a prescription for a given disease, simply piecing together the drugs according to a designed therapeutic principle should be avoided and it is better to follow a traditional prescription and modify it as required in actual situation. 

A traditional prescription is usually chosen based on the pathogenesis of a disease and its reasonable therapeutic principle. Sometimes a prescription may be formulated by selecting drugs simply based on individual conditions, rather than by following any traditional prescription. Nevertheless the therapeutic strategy and philosophy must be embodied in the prescription. Through clinical practice this skill can be gradually gained. Selection of the traditional prescription should be guided by the therapeutic principle and the prescription selected must be consistent with the pathogenesis and the therapeutic principle of the disease.

To choose drugs means to modify a selected prescription by adding or deleting drugs according to the individual case. As clinical manifestations are complicated and variable, it is hard to get a traditional prescription that completely fits the clinical situation. Modification to a traditional prescription is often required. Usually drugs are added to or deleted from a traditional prescription to make a modified one, suitable for both the major problem and complications of a disease. And for individual cases, modifications should be made flexibly so as to achieve desired results.

In summary, the above five-step procedure is followed in the process of syndrome differentiation and treatment for a disease. Actually it includes the four aspects: Li (theory), Fa (principle), Fang (prescription) and Yao (drug). Li refers to the etiology and pathogenesis of the disease; Fa, the therapeutic principle and method; Fang, the traditional prescription; and Yao, the drugs in a prescription. The consistency in these four aspects for a specific disease is the premise for good therapeutic effect. Meanwhile this five-step procedure can be divided into two stages, i.e., stage of syndrome differentiation and stage of treatment. 

Of the five steps, the first three are at the stage of syndrome differentiation, while the rest two at the stage of treatment. It is for the convenience of learning that the procedure in making syndrome differentiation and treatment is divided into five steps or two stages, but clinically it is not necessary to follow it rigidly step by step. When working on a specific disease, a practitioner may follow the procedure in a flexible way. For example, identifying the location and nature of a disease and inferring the cause and judge the pathogenesis of a disease are being conducted when the four diagnostic methods are performed to collect the information for analyzing the disease.