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==Overview==
==Overview==
The diagnosis of gout is based upon the identification of intracellular monosodium urate (MSU) crystals in the synovial fluid aspirate of an affected joint, under polarizing light microscopy. But when this is not possible, a clinical diagnosis can be deduced with the help of classical clinical features, including the history and physical examination, laboratory findings, and various imaging studies.


=== Diagnosis of acute gout ===
In general, '''diagnosis''' (plural ''diagnoses'') has two distinct dictionary definitions. The first definition is "the recognition of a [[disease]] or condition by its outward signs and symptoms", while the second definition is "the analysis of the underlying physiological/biochemical cause(s) of a disease or condition". 
* While the favored approach is to find MSU crystals in the synovial fluid aspirate of an affected joint, in clinical practice a crystal evaluation is routinely not done<ref name="pmid21288096">{{cite journal| author=Neogi T| title=Clinical practice. Gout. | journal=N Engl J Med | year= 2011 | volume= 364 | issue= 5 | pages= 443-52 | pmid=21288096 | doi=10.1056/NEJMcp1001124 | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=21288096  }} </ref><ref name="pmid15014182">{{cite journal| author=Choi HK, Atkinson K, Karlson EW, Willett W, Curhan G| title=Purine-rich foods, dairy and protein intake, and the risk of gout in men. | journal=N Engl J Med | year= 2004 | volume= 350 | issue= 11 | pages= 1093-103 | pmid=15014182 | doi=10.1056/NEJMoa035700 | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=15014182  }} </ref>.
 
* When a patient is presenting with classic symptoms of rapid onset (within 24 hours), podagra, swelling, and erythema, supported by the presence of hyperuricemia, a clinical diagnosis of gout can easily be concluded. <ref>http://pubmed.gov/16707533</ref> <ref>http://pubmed.gov/18299687 <ref>http://pubmed.gov/25789770</ref>
<!--For instance, a common disorder such as [[pneumonia]] was nevertheless used as a diagnosis before the germ theory was accepted, and the disease was defined as a a complex of many symptoms consisting of cough, sputum production, fever and chills.  Later, as the actual cause was assigned to micro-organisms, the term diagnosis included the causality, e.g., pnuemococcal pneumonia, suggesting not only a spectrum of symptoms but also a cause for the symptoms. 
* When an arthrocentesis is done, synovial fluid should be examined readily under routine light and polarizing light microscopy and looked for negatively birefringent needle-shaped MSU crystals. <ref>http://pubmed.gov/13773775</ref>
Advances in medicine could be described as a shift from definition #1 to definition #2 as scientific casualties were discovered. This differentiation of the term diagnosis is critically important because widespread disagreement exists between medical and psychiatric practitioners as to whether casualties for various diseases and disorders are known or unknown.  If casualties are assumed to be known, then authentic cures can be obtained by correcting the causal abnormalities.  If casualties are assumed to be unknown, then palliative treatments to reduce symptoms are the best treatments possible.
* In addition, testing for cell counts with differential, gram staining and culture should also be done on the aspirate.
 
* The sensitivity of this technique in demonstrating negatively birefringent intra- and extracellular crystals in patients with gout flares is at least 85 percent, and the specificity for gout is 100 percent. <ref>http://pubmed.gov/856219</ref> <ref>http://pubmed.gov/16462524</ref>. The sensitivity of can be further improved by examination of the sediment in a centrifuged specimen. <ref>http://pubmed.gov/10803751</ref>
This whole example is unclear and poorly written, and needs to be sifted through somewhere else, as it does not belong in the lead. --->
Diagnosis covers a broad spectrum, or spectra, of testing in some form of analysis; collective reasoning using such tests is called the method of diagnostics, leading then to the results of those tests by ideal (ethics) would then be considered a diagnosis, but not necessarily the correct one.
 
In [[medicine]], '''diagnosis''' or '''diagnostics''' is the process of identifying a medical condition or [[disease]] by its [[sign (medicine)|signs]], [[symptom]]s, and from the results of various diagnostic procedures. The conclusion reached through this process is called ''a diagnosis''. The term "diagnostic criteria" designates the combination of symptoms which allows the doctor to ascertain the diagnosis of the respective disease.
 
Typically, someone with abnormal ''symptoms'' will consult a [[physician]], who will then obtain a history of the [[patient]]'s illness and examine him for ''signs'' of disease. The physician will formulate a hypothesis of likely diagnoses and in many cases will obtain further testing to confirm or clarify the diagnosis before providing treatment.
 
[[Medical test]]s commonly performed are [[blood pressure|measuring blood pressure]], [[pulse|checking the pulse rate]], listening to the heart with a [[stethoscope]], [[urine test]]s, [[fecal test]]s, saliva tests, [[blood test]]s, [[medical imaging]], [[electrocardiogram]], [[Hydrogen Breath Test|hydrogen breath test]] and occasionally [[biopsy]].
 
The word '''diagnosis''' is derived from the [[Greek language|Greek]] words ''dia'' which means "by", and ''gnosis'' which means "knowledge". The verb is ''diagnose'' and a person diagnosing could be considered a ''diagnostician''.
 
== Relationship of diagnosis to medical practice ==
A [[physician]]'s job is to know the human body and its functions in terms of normality ([[homeostasis]]). The four cornerstones of diagnostic medicine, each essential for understanding homeostasis, are: [[anatomy]] (the structure of the human body), [[physiology]] (how the body works), [[pathology]] (what can go wrong with the anatomy and physiology) and [[psychology]] (thought and behavior). Once the doctor knows what is normal and can measure the patient's current condition against those norms, she or he can then determine the patient's particular departure from homeostasis and the degree of departure. This is called the '''diagnosis'''. Once a diagnosis has been reached, the doctor 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 doctor educates the patient about the causes, progression, outcomes, and possible treatments of his ailments, as well as providing advice for maintaining health.
 
It should be noted however, that medical diagnosis in psychology or psychiatry is problematic. Apart from the fact that there are differing theoretical views toward mental conditions and that there are few "lab" tests available for various major disorders (e.g., clinical depression), 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 as well as 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)
 
== Diagnostic procedure ==
Diagnosis is a fluid process in which the physician responds to information garnered from the patient and others, from a physical examination of the patient, and from medical tests performed upon the patient.
 
The doctor should consider the patient in his 'well' context rather than simply as a walking medical condition. This entails assessing the socio-political context of the patient (family, work, stress, beliefs), in addition to the patient's physical body, as this often offers vital clues to the patient's condition and its management.
 
The process of diagnosis begins when the patient consults the doctor and presents a set of complaints (the [[symptoms]]). If the patient is unconscious, this condition is the de facto complaint. The doctor then obtains further information from the patient himself (and from those who know him, if present) about the patient's symptoms, his previous state of health, living conditions, and so forth.
 
Rather than consider the myriad diseases that could afflict the patient, the physician narrows down the possibilities to the [[illness]]es likely to account for the apparent symptoms, making a list of only those [[disease|conditions]] that could account for what is wrong with the patient. These are generally ranked in order of probability.
 
The doctor then conducts a [[physical examination]] of the patient, studies the patient's [[medical record]], and asks further questions as he goes, in an effort to rule out as many of the potential conditions as possible. When the list is narrowed down to a single condition, this is called the [[differential diagnosis]], and provides the basis for a hypothesis of what is ailing the patient.
 
Unless the physician is certain of the condition present, further [[medical test]]s are performed or scheduled (such as [[medical imaging]]), in part to confirm or disprove the diagnosis but also to document the patient's status to keep the patient's medical history up to date. Consultations with other physicians and specialists in the field may be sought. If unexpected findings are made during this process, the initial hypothesis may be ruled out and the physician must then consider other hypotheses.
 
Despite all of these complexities, most patient consultations are relatively brief, because many diseases are obvious, or the physician's experience may enable him to recognize the condition quickly. Another factor is that the [[decision tree]]s used for most diagnostic hypothesis testing are relatively short.
 
Once the physician has completed the diagnosis, he explains the [[prognosis]] to the patient and proposes a treatment plan which includes therapy and follow-up (further consultations and tests to monitor the condition and the progress of the treatment, if needed), usually according to the [[guideline (medical)|guideline]] provided by the medical field on the treatment of the particular illness.
 
Treatment itself may indicate a need for review of the diagnosis if there is a failure to respond to treatments that would normally work.
 
== History of medical diagnostics ==
The history of medical diagnosis began in earnest from the enlightened days of [[Hippocrates]] in ancient Greece but is far from perfect despite the enormous bounty of information made available by medical research including the [[sequencing]] of the [[human genome]]. The practice of diagnosis continues to be dominated by theories set down in the early 1900s.
 
===Ancient Greece===
Over two thousand years ago, Hippocrates recorded the association between disease and heredity. In similar fashion, [[Pythagoras]] noted the association between [[metabolism]] and [[heredity]] (allergy to Fava beans). The medical community, however, has only recently acknowledged the importance of [[genetics]] and its relevance to mainstream [[medicine]].  
 
===The Oslerian ideal===
The ideals of [[William Osler]] who transformed the practice of medicine in the early 1900s were based on the principles of the diagnosis and treatment of [[disease]]. According to Osler, the functions of a [[physician]] were to be able to identify disease and its manifestations, understand its mechanisms, how it may be prevented and how it may be cured. For his medical students he believed that the best textbook was the patient himself – analysis of morbid [[anatomy]] and [[pathology]] were the keys. The Oslerian ideal continues today, as the basis of the Doctor’s strategy is, "What disease does this patient have and what is the best way for treatment?" The emphasis is on the classification of the disease in order to use the remedies available for its effects to be reversed or ameliorated. The human being in question is representative of a class of people with this type of disease whereas the biological individuality of this person is not given any great weight.
 
===Garrod's view===
The successor to William Osler as Regius Professor at Oxford was [[Archibald Garrod]]. Garrod echoed the observations of his Greek counterparts of two millennia ago, ''...our chemical individualities are due to our chemical merits as well as our chemical shortcomings; and it is more nearly true to say that the factors which confer upon us our predispositions to and immunities from various mishaps which are spoken of as diseases, are inherent in our very chemical structure; and even in the molecular groupings which confer upon us our individualities, and which went into the making of the [[chromosomes]] from which we sprang.'' Considering that the time that he formulated these ideas were the early 1900's, and the knowledge of [[DNA]] encoding [[genes]] that in turn encoded [[proteins]] responsible for bodily structure and functions not being discovered until some fifty years later it took some time before medicine could fully appreciate the fundamental importance of his concept of diagnosis.
 
===Present-day Oslerian practice===
Whereas Osler laid the founding principles by which medicine should be practiced, Garrod placed these principles in a greater context of a [[chemical]] individuality that is inherited and is subject to the mechanisms of [[evolutionary]] selection. The Oslerian ideal of medical practice continues to dominate medical philosophy today. The patient is a collective of [[symptoms]] to be characterized and analyzed [[algorithmically]] in order to draw a diagnosis and subsequently produce a strategy of treatment. Medicine is about problems based solutions. In keeping with this philosophy, today's pathology reports provide a momentary snapshot of the patient's [[biochemical]] profile, highlighting the end result of the disease process.  
 
===Influence of DNA technology===
Garrod's conception of biological individuality was confirmed with the advent of the sequencing of the human genome. Finally the subtle relationship between inheritance, individuality and environment became apparent via the variations detected in DNA. In each patient's DNA lies a script for how their bodies will change and become ill as well as how they will handle the assaults of the environment from the beginning of their life to its end. It is hoped that by knowing a patient's genes that the biological strengths and weaknesses in respect to these assaults will be revealed and disease processes can be predicted before they have the opportunity to manifest. Although knowledge in this area is far from complete, there are already medical interventions based on this. More importantly, the physician, forewarned with this knowledge can guide the patient towards appropriate lifestyle changes to anticipate and mitigate disease processes.


{| class="wikitable" align="right"
==See also==
|+ Accuracy of diagnostic criteria for gout among patients who had [[synovial fluid]] analysis
{{col-begin}}
<ref name="pmid19125136">{{cite journal| author=Malik A, Schumacher HR, Dinnella JE, Clayburne GM| title=Clinical diagnostic criteria for gout: comparison with the gold standard of synovial fluid crystal analysis. | journal=J Clin Rheumatol | year= 2009 | volume= 15 | issue= 1 | pages= 22-4 | pmid=19125136 | doi=10.1097/RHU.0b013e3181945b79 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=19125136  }} </ref>
{{col-break}}
! &nbsp;!! Criteria!!Sensitivity !! Specificity
* [[Diagnosis codes]]
|-
* [[Differential diagnosis]]
| ARA (ACR)||6 of 12 criteria||align="center"| 70% ||align="center"| 79%
* [[Diagnosis of exclusion]]
|-
* [[Diagnosis (artificial intelligence)]]
| Rome||2 of 4 criteria:<br/>&bull;&nbsp;Painful joint swelling, abrupt onset, Clearing in 1-2 weeks initially<br/>&bull;&nbsp;Serum uric acid: >7 in males; >6 in females<br/>&bull;&nbsp;Presence of tophi<br/>&bull;&nbsp;Urate crystals in synovial fluid or tissues||align="center"| 70% ||align="center"| 83%
* [[Diagnosis-related group]]
|-
* [[Disease]]
| New York||2 of 5 criteria:<br/>&bull;&nbsp;2 attacks of painful limb joint swelling<br/>&bull;&nbsp;Abrupt onset and remission in 1—2 weeks initially<br/>&bull;&nbsp;First MTP attack<br/>&bull;&nbsp;Presence of a tophus<br/>&bull;&nbsp;Response to colchicine-major reduction in inflammation within 48 h||align="center"| 67% ||align="center"| 89%
* [[Diagnostic and Statistical Manual of Mental Disorders]]
|}
* [[Medicine#Doctor-patient relationship|Doctor-patient relationship]]
Several sets of diagnostic criteria exit (see table).<ref name="pmid19125136">{{cite journal| author=Malik A, Schumacher HR, Dinnella JE, Clayburne GM| title=Clinical diagnostic criteria for gout: comparison with the gold standard of synovial fluid crystal analysis. | journal=J Clin Rheumatol | year= 2009 | volume= 15 | issue= 1 | pages= 22-4 | pmid=19125136 | doi=10.1097/RHU.0b013e3181945b79 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=19125136  }} </ref>
* [[Etiology]]
* [[ICD|International Statistical Classification of<br>Diseases and Related Health Problems (ICD)]]
* [[Medical classification]]
* [[Medical history]]
* [[Medical imaging]]
* [[Medical record]]
* [[Medical test]]
** [[Biopsy]]
** [[Blood pressure]]
** [[Blood test]]s
** [[Diagnostic testing]]
** [[Electrocardiogram]]
** [[Fecal test]]s
*** [[Fecal occult blood|Fecal occult blood test]]
*** [[Fecal fat|Fecal fat test]]
** [[Genetic testing]]
** [[Hydrogen Breath Test|Hydrogen breath test]]
** [[Pulse]]
** [[Saliva test]]s
** [[Stethoscope]]
** [[Urine test]]s and [[urinalysis]]
{{col-break}}
* [[Medicine]]
* [[Mental illness]]
* [[Merck Manual of Diagnosis and Therapy]]
* [[Misdiagnosis]] and [[medical error]]
* [[Nocebo]]
* [[Nosology]]
* [[Nursing diagnosis]]
* [[Pathogenesis]]
* [[Pathology]]
* [[Patient]]
* [[Physical examination]]
* [[Physician]]
* [[Preimplantation genetic diagnosis]]
* [[Prenatal diagnosis]]
* [[Prognosis]]
* [[Pulse diagnosis]]
* [[Reasoning]] applicable to diagnosis:
** [[Abductive reasoning]]
** [[Common sense]]
** [[Deductive reasoning]]
** [[Defeasible reasoning]]
** [[Inductive reasoning]]
** [[Inference]]
** [[Inquiry]]
** [[Retroduction]]
* [[Self diagnosis]]
* [[Therapy]]
* [[Trashcan diagnosis]]
{{col-end}}


{| class="wikitable" align="right"
=== Lists ===
|+ The serum uric acid level during an attack of gout<ref  name="pmid20625017">{{cite journal| author=Janssens HJ, Fransen J,  van de Lisdonk EH, van Riel PL, van Weel C, Janssen M| title=A  diagnostic rule for acute gouty arthritis in primary care without joint  fluid analysis. | journal=Arch Intern Med | year= 2010 | volume= 170 |  issue= 13 | pages= 1120-6 | pmid=20625017 |  url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=20625017  | doi=10.1001/archinternmed.2010.196 }} </ref><ref name="pmid19369457">{{cite journal |author=Schlesinger N, Norquist JM, Watson DJ |title=Serum urate during acute gout |journal=J. Rheumatol. |volume=36 |issue=6 |pages=1287–9 |year=2009 |month=June |pmid=19369457 |doi=10.3899/jrheum.080938 |url=http://www.jrheum.org/cgi/pmidlookup?view=long&pmid=19369457 |issn=}}</ref>
{{col-begin}}
! &nbsp;!! Sensitivity !! Specificity
{{col-break}}
|-
* [[List of diseases]]
| > 5.88 mg/dl<ref  name="pmid20625017"/>|| align="center"|95%|| align="center"|53%
* [[List of disorders]]
|-
{{col-break}}
| ≥ 6 mg/dl<ref name="pmid19369457"/>||align="center"| 86% ||align="center"| ?
* [[List of medical symptoms]]
|-
* [[:Category:Diseases]]
| ≥ 8 mg/dl<ref name="pmid19369457"/>|| align="center"|68% || align="center"|?
{{col-end}}
|}


A [[clinical prediction rule]] ([http://www.umcn.nl/Research/Departments/eerstelijnsgeneeskunde/Pages/Jichtcalculator.aspx online link]) found that the following predicted urate crystals by aspiration:<ref  name="pmid20625017">{{cite journal| author=Janssens HJ, Fransen J,  van de Lisdonk EH, van Riel PL, van Weel C, Janssen M| title=A  diagnostic rule for acute gouty arthritis in primary care without joint  fluid analysis. | journal=Arch Intern Med | year= 2010 | volume= 170 |  issue= 13 | pages= 1120-6 | pmid=20625017 |  url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=20625017  | doi=10.1001/archinternmed.2010.196 }} </ref>
==External links==
* Male
* [http://www.gpnotebook.co.uk/homepage.cfm GPnotebook web site] GPnotebook is a British medical database for [[General practitioners|GP]]s that provides an immediate reference resource for clinicians worldwide. The database consists of over 30,000 pages of information.
* Onset within one day
* [http://icd9coding.com Free 24/7 DRG & ICD-9-CM lookup powered by Flash Code] at icd9coding.com
* Joint redness
* [http://www.thehealthnews.org/differential_diagnosis/index.html Differential Diagnosis]
* First metatarsaophalangeal joint
* [http://www.merck.com/mrkshared/mmanual/home.jsp Merck Manual of Diagnosis and Therapy]
* Previous arthritis attack per patient
* History of hypertension or 1 or more [[cardiovascular disease]]s
* Serum [[uric acid]] level > 5.88 mg/dl


However, among patients with high scores, 20% did not have crystals. Only one of 381 patients had bacterial arthritis.
<br>


=== Diagnosis of intercritical and tophaceous gout ===
[[Category:Diagnosis classification]]
* In patients where a diagnosis of gout wasn’t ascertained during an acute flare, a synovial fluid analysis identifying urate crystals from the previously affected joints would allow a late establishment of the disease.
[[Category:Medical terms]]
* Urate crystals are present in synovial fluid of all untreated gouty patients and in approximately 70 percent of those under urate-lowering therapy. 8624633 10577299 444319
[[Category:Nosology]]
* For tophaceous gout, demonstration of urate crystals in aspirates of tophi provides an easy way to confirm the diagnosis 10834006


=== Clinical diagnosis “rule” for acute gout ===
[[als:Diagnostik]]
* In patients with acute gout where a diagnosis couldn’t be confirmed due to a negative synovial fluid analysis for MSU crystals, a clinical diagnostic approach can be implemented. 20625017
[[bg:Диагноза]]
* This approach utilizes a set of clinical parameters with a scoring value. The parameters are derived from history, clinical presentation, and the laboratory findings. 25231179
[[de:Diagnose]]
* This approach has been shown to improve the accuracy of diagnosis without joint fluid analysis of a gout flare in primary care practice settings 20625017
[[es:Diagnóstico]]
* The model uses seven variables to calculate a total score to distinguish three levels of risk for gout. These are:
[[eu:Diagnostiko]]
*# Male sex (2 points)
[[fr:Diagnostic (médecine)]]
*# Previous patient-reported arthritis flare (2 points)
[[it:Diagnosi]]
*# Onset within one day (0.5 points)
[[he:אבחנה]]
*# Joint redness (1 point)
[[ms:Diagnosis]]
*# First metatarsal phalangeal joint involvement (2.5 points)
[[nl:Diagnose]]
*# Hypertension or at least one cardiovascular disease (1.5 points)
[[ja:診断]]
*# Serum urate level greater than 5.88 mg/dL (3.5 points)
[[no:Diagnose]]
[[nn:Diagnose]]
[[pl:Diagnoza (medycyna)]]
[[pt:Diagnóstico (medicina)]]
[[ro:Diagnostic medical]]
[[simple:Diagnosis]]
[[sk:Diagnóza]]
[[sr:Дијагностика]]
[[sh:Dijagnoza]]
[[fi:Lääketieteellinen diagnoosi]]
[[sv:Diagnostik]]
[[ta:அறுதியிடல்]]
[[zh:诊断]]


* Based upon the total score, patients can be identified as having low (≤4 points), intermediate (>4 to <8 points), or high (≥8 points) probability of having acute gout.
{{jb1}}
* In patients with an intermediate score (>4 but <8 points), a preliminary diagnosis of gout may be made for the purpose of clinical management based upon a prevalent clinical features favoring gout.
{{WikiDoc Help Menu}}
* This diagnostic approach is not recommended for patients presenting with oligoarticular and polyarticular arthritis, as it was developed studying patients with monoarthritis seen by family physicians.  
{{WikiDoc Sources}}

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Sumanth Khadke, MD[2]

Overview

In general, diagnosis (plural diagnoses) has two distinct dictionary definitions. The first definition is "the recognition of a disease or condition by its outward signs and symptoms", while the second definition is "the analysis of the underlying physiological/biochemical cause(s) of a disease or condition".

Diagnosis covers a broad spectrum, or spectra, of testing in some form of analysis; collective reasoning using such tests is called the method of diagnostics, leading then to the results of those tests by ideal (ethics) would then be considered a diagnosis, but not necessarily the correct one.

In medicine, diagnosis or diagnostics is the process of identifying a medical condition or disease by its signs, symptoms, and from the results of various diagnostic procedures. The conclusion reached through this process is called a diagnosis. The term "diagnostic criteria" designates the combination of symptoms which allows the doctor to ascertain the diagnosis of the respective disease.

Typically, someone with abnormal symptoms will consult a physician, who will then obtain a history of the patient's illness and examine him for signs of disease. The physician will formulate a hypothesis of likely diagnoses and in many cases will obtain further testing to confirm or clarify the diagnosis before providing treatment.

Medical tests commonly performed are measuring blood pressure, checking the pulse rate, listening to the heart with a stethoscope, urine tests, fecal tests, saliva tests, blood tests, medical imaging, electrocardiogram, hydrogen breath test and occasionally biopsy.

The word diagnosis is derived from the Greek words dia which means "by", and gnosis which means "knowledge". The verb is diagnose and a person diagnosing could be considered a diagnostician.

Relationship of diagnosis to medical practice

A physician's job is to know the human body and its functions in terms of normality (homeostasis). The four cornerstones of diagnostic medicine, each essential for understanding homeostasis, are: anatomy (the structure of the human body), physiology (how the body works), pathology (what can go wrong with the anatomy and physiology) and psychology (thought and behavior). Once the doctor knows what is normal and can measure the patient's current condition against those norms, she or he can then determine the patient's particular departure from homeostasis and the degree of departure. This is called the diagnosis. Once a diagnosis has been reached, the doctor 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 doctor educates the patient about the causes, progression, outcomes, and possible treatments of his ailments, as well as providing advice for maintaining health.

It should be noted however, that medical diagnosis in psychology or psychiatry is problematic. Apart from the fact that there are differing theoretical views toward mental conditions and that there are few "lab" tests available for various major disorders (e.g., clinical depression), 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 as well as 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)

Diagnostic procedure

Diagnosis is a fluid process in which the physician responds to information garnered from the patient and others, from a physical examination of the patient, and from medical tests performed upon the patient.

The doctor should consider the patient in his 'well' context rather than simply as a walking medical condition. This entails assessing the socio-political context of the patient (family, work, stress, beliefs), in addition to the patient's physical body, as this often offers vital clues to the patient's condition and its management.

The process of diagnosis begins when the patient consults the doctor and presents a set of complaints (the symptoms). If the patient is unconscious, this condition is the de facto complaint. The doctor then obtains further information from the patient himself (and from those who know him, if present) about the patient's symptoms, his previous state of health, living conditions, and so forth.

Rather than consider the myriad diseases that could afflict the patient, the physician narrows down the possibilities to the illnesses likely to account for the apparent symptoms, making a list of only those conditions that could account for what is wrong with the patient. These are generally ranked in order of probability.

The doctor then conducts a physical examination of the patient, studies the patient's medical record, and asks further questions as he goes, in an effort to rule out as many of the potential conditions as possible. When the list is narrowed down to a single condition, this is called the differential diagnosis, and provides the basis for a hypothesis of what is ailing the patient.

Unless the physician is certain of the condition present, further medical tests are performed or scheduled (such as medical imaging), in part to confirm or disprove the diagnosis but also to document the patient's status to keep the patient's medical history up to date. Consultations with other physicians and specialists in the field may be sought. If unexpected findings are made during this process, the initial hypothesis may be ruled out and the physician must then consider other hypotheses.

Despite all of these complexities, most patient consultations are relatively brief, because many diseases are obvious, or the physician's experience may enable him to recognize the condition quickly. Another factor is that the decision trees used for most diagnostic hypothesis testing are relatively short.

Once the physician has completed the diagnosis, he explains the prognosis to the patient and proposes a treatment plan which includes therapy and follow-up (further consultations and tests to monitor the condition and the progress of the treatment, if needed), usually according to the guideline provided by the medical field on the treatment of the particular illness.

Treatment itself may indicate a need for review of the diagnosis if there is a failure to respond to treatments that would normally work.

History of medical diagnostics

The history of medical diagnosis began in earnest from the enlightened days of Hippocrates in ancient Greece but is far from perfect despite the enormous bounty of information made available by medical research including the sequencing of the human genome. The practice of diagnosis continues to be dominated by theories set down in the early 1900s.

Ancient Greece

Over two thousand years ago, Hippocrates recorded the association between disease and heredity. In similar fashion, Pythagoras noted the association between metabolism and heredity (allergy to Fava beans). The medical community, however, has only recently acknowledged the importance of genetics and its relevance to mainstream medicine.

The Oslerian ideal

The ideals of William Osler who transformed the practice of medicine in the early 1900s were based on the principles of the diagnosis and treatment of disease. According to Osler, the functions of a physician were to be able to identify disease and its manifestations, understand its mechanisms, how it may be prevented and how it may be cured. For his medical students he believed that the best textbook was the patient himself – analysis of morbid anatomy and pathology were the keys. The Oslerian ideal continues today, as the basis of the Doctor’s strategy is, "What disease does this patient have and what is the best way for treatment?" The emphasis is on the classification of the disease in order to use the remedies available for its effects to be reversed or ameliorated. The human being in question is representative of a class of people with this type of disease whereas the biological individuality of this person is not given any great weight.

Garrod's view

The successor to William Osler as Regius Professor at Oxford was Archibald Garrod. Garrod echoed the observations of his Greek counterparts of two millennia ago, ...our chemical individualities are due to our chemical merits as well as our chemical shortcomings; and it is more nearly true to say that the factors which confer upon us our predispositions to and immunities from various mishaps which are spoken of as diseases, are inherent in our very chemical structure; and even in the molecular groupings which confer upon us our individualities, and which went into the making of the chromosomes from which we sprang. Considering that the time that he formulated these ideas were the early 1900's, and the knowledge of DNA encoding genes that in turn encoded proteins responsible for bodily structure and functions not being discovered until some fifty years later it took some time before medicine could fully appreciate the fundamental importance of his concept of diagnosis.

Present-day Oslerian practice

Whereas Osler laid the founding principles by which medicine should be practiced, Garrod placed these principles in a greater context of a chemical individuality that is inherited and is subject to the mechanisms of evolutionary selection. The Oslerian ideal of medical practice continues to dominate medical philosophy today. The patient is a collective of symptoms to be characterized and analyzed algorithmically in order to draw a diagnosis and subsequently produce a strategy of treatment. Medicine is about problems based solutions. In keeping with this philosophy, today's pathology reports provide a momentary snapshot of the patient's biochemical profile, highlighting the end result of the disease process.

Influence of DNA technology

Garrod's conception of biological individuality was confirmed with the advent of the sequencing of the human genome. Finally the subtle relationship between inheritance, individuality and environment became apparent via the variations detected in DNA. In each patient's DNA lies a script for how their bodies will change and become ill as well as how they will handle the assaults of the environment from the beginning of their life to its end. It is hoped that by knowing a patient's genes that the biological strengths and weaknesses in respect to these assaults will be revealed and disease processes can be predicted before they have the opportunity to manifest. Although knowledge in this area is far from complete, there are already medical interventions based on this. More importantly, the physician, forewarned with this knowledge can guide the patient towards appropriate lifestyle changes to anticipate and mitigate disease processes.

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