Medical Diagnosis

Medical diagnosis is the process by which healthcare practitioners identify a disease or condition causing a patient's symptoms. It consists of gathering information, comparing different possible conditions, and reaching a conclusion based on available evidence.

Diagnosis is the first step before treatment. The conclusions reached determine the type of medication used, the treatment plan, and advice given to the patient. For this reason, the accuracy and timeliness of the process are evaluated.

Steps in the process

First, the patient's medical history is taken (anamnesis): the patient's complaint, duration of symptoms, previous diseases, current medications, and family history. Next, a physical examination is performed — observation, palpation, percussion, and auscultation. After this, further tests may be ordered such as blood work, urinalysis, imaging (X-ray, ultrasound, CT, MRI), or other laboratory tests.

Differential diagnosis

A single symptom can result from many different diseases. Therefore, the clinician prepares a list of possible conditions and then evaluates each one against the supporting or contradicting evidence. This process is called differential diagnosis. More extensive tests are used to narrow the list.

Classification systems and tools

There are global systems for classifying diseases and diagnoses, most notably the ICD (International Classification of Diseases) maintained by the World Health Organization. Such systems are used in patient records, health statistics, and insurance billing. There are also guidelines that set criteria for confirming specific diseases.

Errors and limitations

Incorrect diagnosis can lead to inappropriate treatment or delayed care. There is also overdiagnosis, where a condition is identified that causes no harm. Common causes include limited information, false positive or negative test results, and limitations in the clinician's knowledge. In recent years, computer programs and artificial intelligence have been tested to assist in diagnosis, but final decisions still rest with healthcare professionals.