In medical

Medicine

Medicine is the science and art of healing. It encompasses a variety of health care practices evolved to maintain and restore health by the prevention and treatment of illness....

 and forensic science, a presumptive test is an analysis of a sample which establishes either:

1. The sample is definitely not a certain substance
2. The sample probably is the substance.

For example, the Kastle-Meyer test

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...

 will show that a sample is not blood, or that the sample is probably blood (but it may be one of a range of less common substances). Further chemical test

Chemical test

In chemistry, a chemical test is a qualitative or quantitative procedure designed to prove the existence of, or to quantify, a chemical compound or chemical group with the aid of a specific reagent...

ing is required 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, which is why presumptive tests are often made to see if confirmatory tests are necessary.

In a like manner, in medicine, a presumptive diagnosis identifies the likely condition a patient has, and a confirmatory diagnosis confirms the presence of the condition.

Examples

• Acid phosphatase test for semen
• Cobalt thiocyanate test‎ for cocaine
• Duquenois-Levine reagent‎ for marijuana
• Kastle-Meyer test
  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...
  
   for blood
• Malachite green test for blood
• Marquis reagent
  Marquis reagent
  The 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...
  
   for narcotics
• Benzidine test
  Benzidine
  Benzidine, the trivial name for 4,4'-diaminobiphenyl, is the solid organic compound with the formula 2. This aromatic amine is a component of a test for cyanide and also in the production of dyes...
  
   for blood which changes from clear to blue in color with the presence of blood

Presumptive testing of contraband samples

The tests for alkaloid

Alkaloid

Alkaloids are a group of naturally occurring chemical compounds that contain mostly basic nitrogen atoms. This group also includes some related compounds with neutral and even weakly acidic properties. Also some synthetic compounds of similar structure are attributed to alkaloids...

s and the Marquis test (performed on TLC

Thin layer chromatography

Thin layer chromatography is a chromatography technique used to separate mixtures. Thin layer chromatography is performed on a sheet of glass, plastic, or aluminum foil, which is coated with a thin layer of adsorbent material, usually silica gel, aluminium oxide, or cellulose...

 plate as per the analytical manual, United States Department of Justice) are presumptive tests. The report obtained after performing these qualitative tests is final when the report is negative in all these tests. There is no need to perform confirmatory tests on negative reports obtained after performing presumptive tests on samples.

A confirmatory test is only required when the presumptive test report is positive for the substance; to confirm the substance's identity, or to measure the percentage purity or other quantitative analysis.

The presence of a substance, even presence at a trace level, can be detected by a presumptive test.

Presumptive test mistake

In March 2010, Australian Customs and Border Protection Service arrested and held for 5 days, a Filipino national at Melbourne Airport

Melbourne Airport

Melbourne Airport , also known as Tullamarine Airport, is the primary airport serving the city of Melbourne and the second busiest in Australia. It was opened in 1970 to replace the nearby Essendon Airport. Melbourne Airport is the sole international airport of the four airports serving the...

 as the result of a presumptive test. A presumptive test swab of a 2.4 kg package of iced tea

Iced tea

Iced tea is a form of cold tea, often served in a glass with ice. It may or may not be sweetened. Iced tea is also a popular packaged drink. It can be mixed with flavored syrup, with common flavors including lemon, peach, raspberry, lime, passion fruit, and cherry...

 powder located in the passenger's baggage returned a positive result for methamphetamine

Methamphetamine

Methamphetamine is a psychostimulant of the phenethylamine and amphetamine class of psychoactive drugs...

 and a second test showed amphetamine

Amphetamine

Amphetamine or amfetamine is a psychostimulant drug of the phenethylamine class which produces increased wakefulness and focus in association with decreased fatigue and appetite.Brand names of medications that contain, or metabolize into, amphetamine include Adderall, Dexedrine, Dextrostat,...

. Subsequent testing showed powder was indeed iced tea.

The Australian Customs and Border Protection Service was ordered to pay A$5,000 as damages to the Filipino.

Recommendations by Federal Drug Administration

The Federal Drug Administration issued a Guidance for Industry and FDA Staff entitled Premarket Submission and Labeling Recommendations for Drugs of Abuse Screening Tests. Its availability was announced in the Federal Register / Vol. 68, No. 231 on Tuesday, December 2, 2003 and is listed under Notices. It is important to understand presumptive testing because of its widespread use by employers and public entities. Most people who take a drug test will take a presumptive test because it is cheaper and faster than other methods of testing. However, it is not as accurate and can render false results. The FDA recommends confirmatory testing to always be conducted and further recommends placing a warning label on the presumptive drug test that reads, "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.