Presumptive tests, in
medical
Medicine is the science and practice of caring for a patient, managing the diagnosis, prognosis, prevention, treatment, palliation of their injury or disease, and promoting their health. Medicine encompasses a variety of health care practic ...
and
forensic science
Forensic science, also known as criminalistics, is the application of science to criminal and civil laws, mainly—on the criminal side—during criminal investigation, as governed by the legal standards of admissible evidence and criminal ...
, analyze a sample and establish one of the following:
#The sample is definitely not a certain substance.
#The sample probably is the substance.
For example, the
Kastle–Meyer test
The Kastle–Meyer test is a presumptive blood test, first described in 1903, in which the chemical indicator phenolphthalein is used to detect the possible presence of hemoglobin. It relies on the peroxidase-like activity of hemoglobin in bloo ...
will show either that a sample is not blood or that the sample is probably blood but may be a less common substance. Further
chemical test
In chemistry, a chemical test is a qualitative or quantitative procedure designed to identify, quantify, or characterise a chemical compound or chemical group.
Purposes
Chemical testing might have a variety of purposes, such as to:
* Determine ...
s are needed to prove that the substance is blood.
Confirmatory tests are the tests required to confirm the analysis. Confirmatory tests cost more than simpler presumptive tests so presumptive tests are often done to see if confirmatory tests are necessary.
Similarly, in medicine, a presumptive diagnosis identifies the likely condition of a patient, and a confirmatory diagnosis is needed to confirm the condition.
Examples
*
Acid phosphatase test for semen
*
Cobalt thiocyanate test for
cocaine
Cocaine (from , from , ultimately from Quechua: ''kúka'') is a central nervous system (CNS) stimulant mainly used recreationally for its euphoric effects. It is primarily obtained from the leaves of two Coca species native to South Am ...
*
Duquenois-Levine reagent for
cannabis
''Cannabis'' () is a genus of flowering plants in the family Cannabaceae. The number of species within the genus is disputed. Three species may be recognized: '' Cannabis sativa'', '' C. indica'', and '' C. ruderalis''. Alternative ...
*
Kastle-Meyer test for blood
*
Malachite green test for blood
*
Marquis reagent Marquis reagent is used as a simple spot-test to presumptively identify alkaloids as well as other compounds. It is composed of a mixture of formaldehyde and concentrated sulfuric acid, which is dripped onto the substance being tested. The United St ...
for narcotics
*
Benzidine test for blood which changes from clear to blue in color with the presence of blood
*
Marquis test for alkaloids
*
Luminol, leuchomalachite green, phenolphthalein, Hemastix, Hemident, and Bluestar are all also used for blood testing
FDA recommendations
The US
Food and Drug Administration
The United States Food and Drug Administration (FDA or US FDA) is a federal agency of the Department of Health and Human Services. The FDA is responsible for protecting and promoting public health through the control and supervision of food ...
issued a ''Premarket Submission and Labeling Recommendations for Drugs of Abuse Screening Tests''. Its availability was announced in the Federal Register, Vol. 68, No. 231 on December 2, 2003 and is listed under "Notices." Presumptive testing has found widespread use by employers and public entities. Most people who take a drug test take a presumptive test, cheaper and faster than other methods of testing. However, it is less accurate and can render false results. The FDA recommends for confirmatory testing to be conducted and the placing of a warning label on the presumptive drug test: "This assay provides only a preliminary result. Clinical consideration and professional judgment should be applied to any drug of abuse test result, in evaluating a preliminary positive result. To obtain a confirmed analytical result, a more specific alternate chemical method is needed.
Gas chromatography/mass spectrometry (GC/MS) is the recommended confirmatory method."
Chemical tests