The Chinese were very observant people. In the China of two or three thousand years ago the doctors had no machines to do tests, or even have a detailed theory of the workings of the body as we understand it in the West today. These techniques were not peculiar to China - virtually every tradition in the world used these methods to diagnose illness. However one has to credit the Chinese with coming up with a system that was so detailed and thorough that both simple diseases like the common cold and very complex diseases like diabetes could be diagnosed. Indeed the system they devised was so refined that problems could be detected even before they had really taken hold as illnesses.
Diagnosis is important but, of course, one needs tools to treat the disease.
Here again the Chinese showed themselves to have extraordinary skills. The two areas where they showed their genius were in Herbal medicine and the development of Acupuncture. We still use them today in the west in much the same way we did thousands of years ago. Also many of the drugs used in orthodox medicine have been derived from herbs. However the Chinese materia medica is perhaps the most detailed herbal available to us to this day showing how advanced they were in their thinking.