Medical diagnosis (often simply termed diagnosis) refers both to the process of attempting to determine or identify a possible disease or disorder (and diagnosis in this sense can also be termed (medical) diagnostic procedure), and to the opinion reached by this process (also being termed (medical) diagnostic opinion). From the point of view of statistics the diagnostic procedure involves classification tests. It is a major component of, for example, the procedure of a doctor's visit.
The plural of diagnosis is diagnoses, the verb is to diagnose, and a person who diagnoses is called a diagnostician. The word diagnosis (/daɪ.əɡˈnoʊsɨs/) is derived through Latin from the Greek word διαγιγνώσκειν, meaning to discern or distinguish.[1] This Greek word is formed from διά, meaning apart, and γιγνώσκειν, meaning to perceive.
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A diagnosis, in the sense of diagnostic procedure, can be regarded as an attempt at classification of a an individual's condition into separate and distinct categories that allow medical decisions about treatment and prognosis to be made. Subsequently, a diagnostic opinion is often described in terms of a disease or other condition, but in the case of a wrong diagnosis, the individual's actual disease or condition is not the same as the individual's diagnosis.
A diagnostic procedure may be performed by various health care professionals such as a physician, physical therapist, chiropractor, healthcare scientist, dentist, podiatrist, nurse practitioner, or physician assistants. This article uses diagnostician as any of these person categories.
A diagnostic procedure (as well as the opinion reached thereby) does not necessarily involve elucidation of the etiology of the diseases or conditions of interest, that is, what caused the disease or condition. Such elucidation can be useful to optimize treatment, further specify the prognosis or prevent recurrence of the disease or condition in the future.
However, a diagnosis can take many forms.[2] It might be a matter of naming the disease, lesion, dysfunction of disability. It might be a management-naming or prognosis-naming exercise. It may indicate either degree of abnormality on a continuum or kind of abnormality in a classification. It’s influenced by non-medical factors such as power, ethics and financial incentives for patient or doctor. It can be a brief summation or an extensive formulation, even taking the form of a story or metaphor. It might be a means of communication such as a computer code through which it triggers payment, prescription, notification, information or advice. It might be pathogenic or salutogenic. It’s generally uncertain and provisional.
It should be noted that medical diagnosis in psychology or psychiatry is problematic. There are differing theoretical views toward mental conditions and few objective tests available for various major disorders (e.g., clinical depression), so a causal analysis with respect to symptomatology and disorder/disease is not always possible. As a result, most if not all mental conditions function as both symptoms and disorders. There are often functional descriptions provided for psychological disorders and these are vulnerable to circular reasoning due to the etiological fuzziness inherent of these diagnostic categories. (BDG, 2006)
The initial task is to detect a medical indication to perform a diagnostic procedure. Indications include:
Even during an already ongoing diagnostic procedure, there can be an indication to perform another, separate, diagnostic procedure for another, potentially concomitant, disease or condition. This may occur as a result of an incidental finding of a sign unrelated to the parameter of interest, such as can occur in comprehensive tests such as radiological studies like magnetic resonance imaging or blood test panels that also include blood tests that are not relevant for the ongoing diagnosis.
General components, which are present in a diagnostic procedure in most of the various available methods include:
There are a number of methods or techniques that can be used in a diagnostic procedure, including performing a differential diagnosis or following medical algorithms.[4] In reality, a diagnostic procedure may involve components of multiple methods.[5]
The method of differential diagnosis is based on finding as many candidate diseases or conditions as possible that can possibly cause the signs or symptoms, followed by a process of elimination or at least of rendering the entries more or less probable by further medical tests and other processing until, aiming to reach the point where only one candidate disease or condition remains as probable. The final result may also remain a list of possible conditions, ranked in order of probability or severity.
The resultant diagnostic opinion by this method can be regarded more or less as a diagnosis of exclusion. Even if it doesn't result in a single probable disease or condition, it can at least rule out any imminently life-threatening conditions.
Unless the provider is certain of the condition present, further medical tests, such as medical imaging, are performed or scheduled in part to confirm or disprove the diagnosis but also to document the patient's status and keep the patient's medical history up to date.
If unexpected findings are made during this process, the initial hypothesis may be ruled out and the provider must then consider other hypotheses.
In a pattern recognition method the provider uses experience to recognize a pattern of clinical characteristics.[4] It is mainly based on certain symptoms or signs being associated with certain diseases or conditions, not necessarily involving the more cognitive processing involved in a differential diagnosis.
This may be the primary method used in cases where diseases are "obvious", or the provider's experience may enable him or her to recognize the condition quickly. Theoretically, a certain pattern of signs or symptoms can be directly associated with a certain therapy, even without a definite decision regarding what is the actual disease, but such a compromise carries a substantial risk of missing a diagnosis which actually has a different therapy so it may be limited to cases where no diagnosis can be made.
The term diagnostic criteria designates the specific combination of signs, symptoms, and test results that the clinician uses to attempt to determine the correct diagnosis.
Some examples of diagnostic criteria are:
Clinical decision support systems are interactive computer programs designed to assist health professionals with decision-making tasks. The clinician interacts with the software utilizing both the clinician’s knowledge and the software to make a better analysis of the patients data than either human or software could make on their own. Typically the system makes suggestions for the clinician to look through and the clinician picks useful information and removes erroneous suggestions.[6]
Other methods that can be used in performing a diagnostic procedure include:
Once a diagnostic opinion has been reached, the provider is able to propose a management plan, which will include treatment as well as plans for follow-up. From this point on, in addition to treating the patient's condition, the provider can educate the patient about the etiology, progression, prognosis, other outcomes, and possible treatments of her or his ailments, as well as providing advice for maintaining health.
A treatment plan is proposed which may include therapy and follow-up consultations and tests to monitor the condition and the progress of the treatment, if needed, usually according to the medical guidelines provided by the medical field on the treatment of the particular illness.
Relevant information should be added to the medical record of the patient.
A failure to respond to treatments that would normally work may indicate a need for review of the diagnosis.
Sub-types of diagnoses include:
Overdiagnosis is the diagnosis of "disease" that will never cause symptoms or death during a patient's lifetime. It is a problem because it turns people into patients unnecessarily and because it can lead to economic waste (overutilization) and treatments that may cause harm. Overdiagnosis occurs when a disease is diagnosed correctly, but the diagnosis is irrelevant. A correct diagnosis may be irrelevant because treatment for the disease is not available, not needed, or not wanted.
Causes and factors of error in diagnosis are:[7]
When making a medical diagnosis, a lag time is a delay in time until a step towards diagnosis of a disease or condition is made. Types of lag times are mainly:
The history of medical diagnosis began in earnest from the days of Imhotep in ancient Egypt and Hippocrates in ancient Greece. In Traditional Chinese Medicine, there are four diagnostic methods: inspection, auscultation-olfaction, interrogation, and palpation.[9] A Babylonian medical textbook, the Diagnostic Handbook written by Esagil-kin-apli (fl. 1069-1046 BC), introduced the use of empiricism, logic and rationality in the diagnosis of an illness or disease.[10] The book made use of logical rules in combining observed symptoms on the body of a patient with its diagnosis and prognosis.[11] Esagil-kin-apli described the symptoms for many varieties of epilepsy and related ailments along with their diagnosis and prognosis.[12]
The practice of diagnosis continues to be dominated by theories set down in the early 20th century.
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