Medical diagnosis

Diagnosis, in common understanding, is the determination or ascertainment of a disease. The word is derived from ancient Greek διάγνωσις diágnosis, German 'Unterscheidung', 'decision' (consisting of διά- diá-, German 'durch-' and γνώσις gnósis, German 'Erkenntnis', 'judgment').

A diagnosis is made by summarising and assessing the overall findings. This may, for example, involve individual complaints and signs of illness (symptoms) or typical symptom combinations (syndrome). Normal findings or non-pathological deviations from the norm can also contribute to the diagnosis. These findings are collected by systematic questioning (anamnesis), by physical examination and by chemical or instrumental tests. The diagnosis is decisive for the further course of treatment.

In medical classification systems, such as the International Classification of Diseases (ICD), diagnoses are schematically divided into groups and thus roughly mapped. The term diagnosis is also used in psychology (see Psychological Diagnostics). In the nursing field, a nursing diagnosis refers to a condition or a health problem that justifies or influences nursing measures.

Ways to the diagnosis

The path to a diagnosis is also referred to as diagnosis and typically ends with the naming of the clinical picture found. The naming often includes ideas about the cause and origin of the disease (aetiology and pathogenesis). The diagnosis can be purely clinical (already fundamentally presented in the Hippocratic writings). Mostly, however, it is a targeted sequence of different examinations, e.g. psychological diagnostics or imaging diagnostics.

By the term routine diagnostics may be meant:

• a measure that can be carried out without special effort, without extra requirement (e.g. for laboratories)
• a sequence of measures carried out without concrete suspicion (e.g. in the case of screening, "check it out")
• a measure to be implemented in treatment guidelines for clinical symptoms (e.g.: posterior wall infarction)
• a measure to be carried out in treatment protocols at fixed time intervals

Types of diagnoses

In the ideal case, the individual findings that have been collected come together to form a unified picture and allow only one definite diagnosis to be made. However, it is not possible to work out certain diagnoses in all cases, which is why certain traditional terms have become established that refer to the degree of certainty of a diagnosis.

Diagnosis of exclusion

Diagnosis by exclusion is a diagnosis that results from the gradual exclusion of all other possible diseases with the same symptoms until only the diagnosis by exclusion remains.

Suspicious and working diagnosis

If neither diagnostics nor differential diagnostics provide a definite result, the suspected diagnosis is preceded by V. a. (suspected). The terms suspected and working diagnosis are often used synonymously. They are basically the starting point for further investigations to confirm or reject a suspicion. In emergency medicine, the term working diagnosis is used for symptom complexes that can only be differentiated in more detail with a time delay in the course of emergency medical care or in an emergency department, because the necessary laboratory or other examinations, such as computer tomography or conventional X-ray diagnostics, take a corresponding amount of time. Examples of this are acute coronary syndrome and polytrauma.

Reasons for limiting oneself to a justified suspicion, i.e. not making an exact diagnosis, typically lie in the fact that further examinations are not in reasonable proportion to the therapeutic consequence, are rejected by the patient or involve a health risk for the patient. A lack of possibilities or time (for example, in an emergency) or cost reasons may also stand in the way. For example, the diagnosis of influenza infection is always a tentative diagnosis as long as no virological examination has been performed. Similarly, in emergency medicine the term acute coronary syndrome has become established, which ultimately covers all symptoms of reduced blood flow to the heart. The differentiation between angina pectoris and myocardial infarction is then two-sided.

Differential diagnosis

Differential diagnosis (also differential diagnosis; abbreviated DD on diagnostic reports) is the term used to describe the totality of all diagnoses that are to be considered or have been considered as alternative explanations for the symptoms (signs of illness) or medical findings recorded. A systematic differential diagnosis as a subject of nosology is first found in the writings of the Roman physician Caelius Aurelianus in the 5th century.

Diagnosis ex juvantibus

In cases where the diagnosis has not been established with certainty, it is occasionally possible to infer the correctness of an original diagnosis by a trial application of therapy on the basis of an observed improvement in the clinical picture or a cure ex post. This is called Diagnosis ex juvantibus (diagnosis from healing success).

Misdiagnosis

An incorrectly made diagnosis is called a misdiagnosis. The causes can be, for example, incorrect applications in the laboratory methods. Often, a wrong diagnosis is blamed on the doctors. In 2010, the medical profession's review boards identified incorrect diagnoses or treatments in 2,199 patients, resulting in 87 deaths. According to experts, however, the error rate is low in view of the approximately 400 million doctor-patient contacts per year.