Diagnostic test

A diagnostic test is any kind of medical procedure performed to aid in the diagnosis or detection of disease. For example:

* to diagnose diseases
* to measure the progress or recovery from disease
* to confirm that a person is free from disease

A drug test can be a specific medical test to acertain the presence of a certain drug in the body (for example, in drug addicts).

## Contents

* 1 Overview
* 1.1 Properties
* 1.2 Bayesian probability and performance metrics
* 2 Types of medical tests
* 2.1 Consulting room tests
* 2.2 More invasive examinations requiring sterile procedures
* 2.3 Requiring laboratory analysis
* 2.4 Requiring microscopy
* 2.5 Requiring elaborate medical equipment
* 3 Psychological effects of diagnostic tests
* 4 See also
* 5 References
* 6 External links

## Overview

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Some medical tests are parts of a simple physical examination which require only simple tools in the hands of a skilled practitioner, and can be performed in an office environment. Some other tests require elaborate equipment used by medical technologists or the use of a sterile operating theatre environment.

Some tests require samples of tissue or body fluids to be sent off to a pathology lab for further analysis. Some simple chemical tests, such as urine pH, can be measured directly in the doctor's office.

Most medical tests are conducted on the living; however, some of these tests can also be carried out on a dead person as part of an autopsy.

Medical tests can be classified into three categories:

* invasive
* minimally invasive
* non-invasive

### Properties

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The result of a test may be positive or negative: this has nothing to do with a bad prognosis, but rather means that the test worked or not, and a certain parameter that was evaluated was present or not. For example, a negative screening test for breast cancer means that no sign of breast cancer could be found (which is in fact very positive for the patient).

### Bayesian probability and performance metrics

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Other characteristics of tests include:

* sensitivity
* specificity
* positive predictive value
* negative predictive value
* false positive
* false negative

Methods to compare diagnostic tests  Method | Advantages | Disadvantages

|
|

Simple accuracy | Easy to understand | Varies with prevalence of disease
Gain in Certainty[1]
(Sensitivity plus specificity) | Easy to understand
Stable with prevalence of disease |
Youden's J index[2]
(Sensitivity plus specificity minus 1) | Easy to understand
Stable with prevalence of disease |
Area under the receiver operating characteristic curve (AROC)[3]and variations[4] | Stable with prevalence of disease
Can interpret multi-level and continuous outcome tests | Hard to understand
Diagnostic odds ratio (DOR)[5] | Stable with prevalence of disease
Can be included in multivariable analyses | Hard to understand
Underestimates heterogeneity[6]
Net reclassification index[7][8]
Change in sensitivity plus change in specificity | Stable with prevalence of disease
Can interpret multi-level tests | Hard to understand
Net reclassification example

## Types of medical tests

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### Consulting room tests

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* auscultation, including listening with a stethoscope
* weighing, and measuring height and girth
* measuring blood pressure
* taking the patient's pulse
* breath tests
* reflex tests
* eye examination
* ophthalmoscopy
* hearing test
* digital rectal examination
* vaginal examination

### More invasive examinations requiring sterile procedures

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* biopsies
* lumbar puncture

### Requiring laboratory analysis

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* urine tests
* stool samples
* saliva samples
* hair samples
* blood tests
* ESR
* CBC (complete blood count)
* CMP (comprehensive metabolic panel)
* blood gas monitor
* DNA tests

### Requiring microscopy

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* Pap smears

### Requiring elaborate medical equipment

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* X-rays
* barium enema
* intravenous pyelogram (IVP test)
* ultrasound scans
* electrocardiogram (EKG)
* electroencephalogram (EEG)
* computer aided tomography scans
* positron emission tomography (PET)
* magnetic resonance imaging (MRI)
* functional MRI
* endoscopy
* colonoscopy
* cystoscopy
* sigmoidoscopy
* colposcopy

## Psychological effects of diagnostic tests

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Medical tests can have value when results are abnormal by explaining to a patient the cause of their symptoms[9]. In addition, normal test results can have value by reassuring patients that serious illness is not present and even reduce the rates of subsequent symptoms [10]. Understanding the meaning of a normal test in advance of learning the test results may also reduce the rates of subsequent symptoms [11].

Lack of adequate education about the meaning of test results (especially relevant to tests that may have incidental and unimportant findings) may cause an increase in symptoms [12]. In addition, the possible benefits must be weighed against the costs of unnecessary tests and resulting unnecessary follow-up and possibly even unnecessary treatment of incidental findings [13].

## See also

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* Medical record
* Physical examination

## References

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1. ↑ Connell FA, Koepsell TD (1985). "Measures of gain in certainty from a diagnostic test". Am. J. Epidemiol. 121 (5): 744–53. PMID 4014166. Unknown parameter `|month=` ignored (help)
2. ↑ Youden WJ (1950). "Index for rating diagnostic tests". Cancer. 3 (1): 32–5. PMID 15405679. Unknown parameter `|month=` ignored (help)
3. ↑ Hanley JA, McNeil BJ (1982). "The meaning and use of the area under a receiver operating characteristic (ROC) curve". Radiology. 143 (1): 29–36. PMID 7063747.
4. ↑ Leeflang MM, Deeks JJ, Gatsonis C, Bossuyt PM, Cochrane Diagnostic Test Accuracy Working Group (2008). "Systematic reviews of diagnostic test accuracy". Ann Intern Med. 149 (12): 889–97. PMID 19075208.CS1 maint: Multiple names: authors list (link)
5. ↑ Glas AS, Lijmer JG, Prins MH, Bonsel GJ, Bossuyt PM (2003). "The diagnostic odds ratio: a single indicator of test performance". J Clin Epidemiol. 56 (11): 1129–35. PMID 14615004.CS1 maint: Multiple names: authors list (link)
6. ↑ Cornell J, Mulrow CD, Localio AR (2008). "Diagnostic test accuracy and clinical decision making". Ann Intern Med. 149 (12): 904–6. PMID 19075211.CS1 maint: Multiple names: authors list (link)
7. ↑ Kerr KF, Wang Z, Janes H, McClelland RL, Psaty BM, Pepe MS (2014). "Net reclassification indices for evaluating risk prediction instruments: a critical review". Epidemiology. 25 (1): 114–21. doi:10.1097/EDE.0000000000000018. PMC 3918180. PMID 24240655.CS1 maint: Multiple names: authors list (link)
8. ↑ Pencina MJ, D'Agostino RB, D'Agostino RB, Vasan RS (2008). "Evaluating the added predictive ability of a new marker: from area under the ROC curve to reclassification and beyond". Stat Med. 27 (2): 157–72, discussion 207-12. doi:10.1002/sim.2929. PMID 17569110.CS1 maint: Multiple names: authors list (link)
9. ↑ Ward B, Wu W, Richter J, Hackshaw B, Castell D (1987). "Long-term follow-up of symptomatic status of patients with noncardiac chest pain: is diagnosis of esophageal etiology helpful?". Am J Gastroenterol. 82 (3): 215–8. PMID 3826028.CS1 maint: Multiple names: authors list (link)
10. ↑ Sox H, Margulies I, Sox C (1981). "Psychologically mediated effects of diagnostic tests". Ann Intern Med. 95 (6): 680–5. PMID 7305144.CS1 maint: Multiple names: authors list (link)
11. ↑ Petrie K, Müller J, Schirmbeck F, Donkin L, Broadbent E, Ellis C, Gamble G, Rief W (2007). "Effect of providing information about normal test results on patients' reassurance: randomised controlled trial". BMJ. 334: 352. PMID 17259186.CS1 maint: Multiple names: authors list (link)
12. ↑ Kendrick D, Fielding K, Bentley E, Kerslake R, Miller P, Pringle M (2001). "Radiography of the lumbar spine in primary care patients with low back pain: randomised controlled trial". BMJ. 322 (7283): 400–5. PMID 11179160.CS1 maint: Multiple names: authors list (link)
13. ↑ Jarvik J, Hollingworth W, Martin B, Emerson S, Gray D, Overman S, Robinson D, Staiger T, Wessbecher F, Sullivan S, Kreuter W, Deyo R (2003). "Rapid magnetic resonance imaging vs radiographs for patients with low back pain: a randomized controlled trial". JAMA. 289 (21): 2810–8. PMID 12783911.CS1 maint: Multiple names: authors list (link)

## External links

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* Diagnostic medical tests \- Informative, educational and user- friendly web site that offers valuable information about laboratory services, diagnostic and medical tests with comprehensive references and information.

* Detecting breast cancer earlier \- Breast cancer research foundation web site. Information on breast cancer medical researches that demonstrates the potential for discovering earlier methods of detecting breast cancer.

de:Medizinische Untersuchung sr:Дијагностички тест