Diagnostic test
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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).
Overview[edit | edit source]
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:
Properties[edit | edit source]
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[edit | edit source]
Other characteristics of tests include:
- sensitivity
- specificity
- positive predictive value
- negative predictive value
- false positive
- false negative
| 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 |
Types of medical tests[edit | edit source]
Consulting room tests[edit | edit source]
- 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
- hearing test
- digital rectal examination
- vaginal examination
More invasive examinations requiring sterile procedures[edit | edit source]
Requiring laboratory analysis[edit | edit source]
- 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[edit | edit source]
Requiring elaborate medical equipment[edit | edit source]
- X-rays
- barium enema
- intravenous pyelogram (IVP test)
- ultrasound scans
- electrocardiogram (EKG)
- electroencephalogram (EEG)
- computer aided tomography scans
- endoscopy
Psychological effects of diagnostic tests[edit | edit source]
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[edit | edit source]
References[edit | edit source]
- ↑ 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) - ↑ Youden WJ (1950). "Index for rating diagnostic tests". Cancer. 3 (1): 32–5. PMID 15405679. Unknown parameter
|month=ignored (help) - ↑ 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.
- ↑ 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.
- ↑ 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.
- ↑ Cornell J, Mulrow CD, Localio AR (2008). "Diagnostic test accuracy and clinical decision making". Ann Intern Med. 149 (12): 904–6. PMID 19075211.
- ↑ 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.
- ↑ 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.
- ↑ 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.
- ↑ Sox H, Margulies I, Sox C (1981). "Psychologically mediated effects of diagnostic tests". Ann Intern Med. 95 (6): 680–5. PMID 7305144.
- ↑ 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.
- ↑ 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.
- ↑ 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.
External links[edit | edit source]
- 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.
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