ABSTRACT
The process of diagnosis begins with eliciting the patient's presenting complaint; there are approximately 40 complaints that commonly present to general physicians. There then follows a process of information gathering, consisting of the history, examination and investigations. The history is the most important part of the clinical evaluation. The information elicited from the history may be divided into two main categories. First, the presenting complaint and the history of the presenting complaint provide the story of the patient's illness, sometimes known as the 'illness script.' Secondly, the personal details, drug history, family history and social history provide the context in which the illness script may be interpreted. The purpose of diagnostic tests is to provide information that makes a given diagnosis either more or less likely. The probability of the diagnosis before the test is carried out is known as the pre-test probability, while the probability of the diagnosis taking into account the test result is the post-test probability.
