Four factors that are important to Health Economics: Government Intervention, Uncertainty, Asymmetric Knowledge, and Externalities.
Governments tend heavily regulate the Healthcare industry and also tend to be the largest payor within the market. Uncertainty is intrinsic to health, both in patient outcomes and financial concerns.
The knowlege gap that exists between a physician and a patient creates a situation of distinct advantage for the physician, which is called Asymmetric Knowledge. Finally, there are many effects that happen between two parties without monetary compensation, called externalities, within healthcare, from catching a cold from someone to practicing safe sex.
The scope of health economics is neatly encapsulated by Alan William's 'plumbing diagram' dividing the discipline into eight distinct topics:
what influences health? (other than health care)
what is health and what is its value?
the demand for health care (e.g. occupational health and carpal tunnel syndrome)
the supply of health care (rapid diagnosis with innovative new method)
micro-economic evaluation at treatment level
evaluation at whole system level; and, (innovations are changing operational processes)
planning, budgeting and monitoring mechanisms. (cities and municipalities)
Helge: the (red) is added by me to relate this definition to Mediracer and CTS point of care diagnostics.