Diagnosis – the process of determining from what disease or ailment a patient is suffering by analysis of their symptoms and signs – is an integral component of modern medical care. It allows for the medical practitioner to establish a course of treatment on the basis of rational knowledge. As the renowned physician Martin H. Fischer observed: ‘Diagnosis is not the end, but the beginning of practice.’
The modern doctor looks to a number of indicators when attempting to make a diagnosis. These include reported symptoms by a patient, along with the patient’s medical history. There may then be tests to discern any changes from the normal within the patient, whether in terms of anatomy (e.g. a rash) a change in blood-sugar levels, functioning or mental state. It is often the case that a diagnostician will be confronted with a number of possible candidate diseases or conditions, which by a process of elimination they will attempt to rank in terms of likelihood. This is known as differential diagnosis.
The evolution of diagnosis
Over the course of history, diagnosis has taken many forms: divination was employed in some ancient cultures, while astrology remained a tool in European medicine well into the medieval age. However, methods more in line with current thinking were in practice at least as far back as the 11th century BCE, when the Babylonian Esagil-kin-apli wrote a diagnostic handbook based on the rational consideration of physical indicators.
Hippocrates was another early innovator, not least in his use of urine as an indicator of disease. Nonetheless, he was less interested in diagnosis than prognosis – that is to say, predicting the likely outcome of a patient’s overall medical situation. Having established a prognosis – as discussed in the previous entry – he would then formulate a holistic programme of treatment, often centred upon imbalances in the humours.
Right up until the 19th century, there was tension between those who regarded the physician’s role as to provide a general prognosis and those who thought he should offer a specific diagnosis. However, diagnosis is now commonly accepted as the precursor to establishing the most effective, targeted treatments. The job of diagnosis has also greatly benefited from technical innovations – from stethoscopes and X-rays to ultrasounds and genetic testing – granting the modern doctor the tools to diagnose with a hitherto unimaginable level of accuracy.