Internal medicine is the most extensive clinical discipline that covers various categories of internal diseases. Other diseases often present manifestations similar to those of internal diseases at the early stage. Therefore it is important to differentiate them and form a sound judgement. By fulfilling the following requirements, a practitioner may avoid making incorrect diagnosis and delaying treatment for patients.

For making correct syndrome differentiation and diagnosis, it is a premise to collect the complete information by using the four diagnostic methods and referring to the results from physical and laboratory examinations. Inaccurate or incomplete information often leads to an incorrect diagnosis and syndrome differentiation. Clinically the symptoms and signs of internal diseases are complicated and volatile. Some of them are consistent with the fundamental nature of the disease, but some are not. 

When the phenomena (symptoms and signs) are not consistent with the nature of the disease, the inconsistency will appear as false phenomena, e.g., false pulses, false tongue pictures or false symptoms. Therefore a careful and comprehensive analysis of a patient's condition is needed to enable practitioners to identify false phenomena and ensure a correct diagnosis.   

The holistic view in TCM is important in making an overall analysis of a patient's condition and directs the syndrome differentiation. It infers a state of completeness and unity, that is, harmony among all parts of the human body and harmony between human beings and the universe. This view postulates that all parts of the human body are associated with each other, and that the skin, muscles, tendons and tissues, meridian system and internal organs are closely associated to form an organic whole. 

Therefore a regional disease may have systemic manifestations, while a systemic disease may have localized symptoms and signs. An interior disorder may present symptoms and signs on the exterior, while an exterior disease may affect internal organs. The dysfunction of internal organs will lead to the disturbance of emotions, while emotional disorders will injure the internal organs directly. For that reason, regional examination and systemic examinations are equally important. Meanwhile the age, sex, occupation and working conditions of a patient should also be taken into account, as they may be related to the development of certain diseases. Finally it should not be neglected that the nature, including seasons, climates and geographical environments, has a great impact on the human body.

 

To differentiate principal and secondary aspects is an important step in determining the strategy and priority of treatment. Biao, the branch or the secondary aspect of a disease, refers to the manifestation of a disease, and Ben, the root or the principal aspect, refers to fundamental nature of a disease. The principal and secondary aspects of diseases are not a fixed pattern. In terms of the cause and manifestation of a disease, the former is the principal aspect, and the latter is the secondary aspect. In term of a disease with two focuses, the primary focus is the principal aspect, and the secondary focus is the secondary aspect. 

In term of the symptoms of a disease, the primary symptom is the principal aspect, and the secondarily developed symptom is the secondary aspect. In term of the clinical course of a disease, the original disorder is the principal aspect, and the newly developed disorder is the secondary aspect. To differentiate the principal and secondary aspects enables practitioners to find out the essential aspect of the disease, so that they make accurate diagnosis and provide proper treatment.

After the principal and secondary aspects are identified, the priority of treatment may be given to either principal or secondary aspect of the disease according to the severity and urgency of the disease. It is rational to treat the principal aspect first if the principal aspect is urgent and serious, and give the priority of treatment to the secondary aspect or treat principal and secondary aspects simultaneously if the secondary aspect of the disease appears acute and serious. 

However, the principal aspect and secondary aspect in a disease may affect each other and transform from one into the other. A treatment for the principal aspect of a disease may benefit the secondary aspect, and vice versa. For instance, strengthening the anti-pathogenic qi, a method of treating the principal aspect, will facilitate eliminating pathogenic factors. Meanwhile treatment of eliminating pathogenic factors will promote the recovery of anti-pathogenic qi.

Clinically when dealing with a given disease a practitioner should identify the dominant aspect of the disease. The dominant aspect of a disease, which may be brought out only through analyzing the etiology and pathogenesis of the disease, does not necessarily appear frequently or obviously. The dominant aspect is the symptoms or signs that reflect the fundamental pathogenesis, and dominates the development of the disease. Concentration on the dominant symptoms and signs is an important part of a therapeutic strategy.

 

A syndrome may change through the course of the disease. A cold syndrome may be transformed into a heat one, a heat syndrome into a cold one, a deficiency syndrome into an excess one, and an excess syndrome into a deficiency one. However, the transformation of syndromes depends on various factors such as body constitution of the patient, climate, diet, emotions, drugs used, etc. Some factors may facilitate the transformation and should be carefully monitored. As soon as a transformation is observed, intervention should be given promptly and accordingly.

 

When a series of characteristic and consistent symptoms and signs appear, it is relatively easier for a practitioner to make a conclusive diagnosis. However, the manifestations of many diseases are not typical, and there may I be inconsistency or paradox in the symptoms or signs that appear in a disease. Clinically often encountered are false I phenomena such as false cold manifestations in a heat syndrome, false heat manifestations in a cold syndrome, false deficiency manifestations in an extreme excess syndrome, and false excess manifestations in an extreme deficiency syndrome. 

In some cases, the nature of a disease is too complicated to be understood thoroughly, then practitioners should analyze the fundamental nature of the disease  carefully, differentiate the true from the false, and the fundamental aspect from the non-fundamental aspect. Probably, many manifestations of a disease are false phenomena and only one or two symptoms and signs reflect its fundamental nature. But it is these symptoms and signs that provide evidence for syndrome differentiation. It is vital not to be confused by the false phenomena. 

Generally speaking, information from tongue inspection and pulse taking is indicative of the cold or heat nature of a disease. Of course, the information collected from the interrogation is valuable too. As for indicators of a heat or cold syndrome, they can be obtained by using the four diagnostic methods. Furthermore, factors such as constitution, age, history and course of disease, diet, emotions and administration of medicines, will provide important clues for the differentiation between cold and heat syndromes