Editing Titer

{{Short description|Way of expressing concentration}}
{{Use American English|date=April 2021}}
{{Use mdy dates|date=April 2021}}

'''Titer''' ([[American English]]) or '''titre''' ([[British English]]) is a way of expressing [[concentration]].<ref name="KaplittLoewy1995">{{cite book|author1=Michael G. Kaplitt|author2=Arthur D. Loewy|title=Viral vectors: gene therapy and neuroscience applications|url=https://books.google.com/books?id=bKqy7YvJpoIC&pg=PA304|access-date=18 March 2012|date=1 August 1995|publisher=Academic Press|isbn=978-0-12-397570-6|pages=304}}</ref> Titer testing employs [[serial dilution]] to obtain approximate quantitative information from an analytical procedure that inherently only evaluates as positive or negative. The titer corresponds to the highest dilution factor that still yields a positive reading.<ref name="Timbury1994">{{cite book|author=Morag Crichton Timbury|title=Notes on medical virology|url=https://books.google.com/books?id=4ZNrAAAAMAAJ|access-date=18 March 2012|year=1994|publisher=Churchill Livingstone|isbn=978-0-443-04872-2|page=27}}</ref> For example, positive readings in the first 8 serial, twofold dilutions translate into a titer of [[Ratio|1:256]] (i.e., 2<sup>−8</sup>). Titres are sometimes expressed by the denominator only, for example 1:256 is written 256.<ref name="FoxBienstock2010">{{cite book|author1=Harold E. Fox|author2=Jessica Bienstock|title=The Johns Hopkins Manual of Gynecology and Obstetrics|url=https://books.google.com/books?id=4Sg5sXyiBvkC&pg=PR226|access-date=18 March 2012|date=21 December 2010|publisher=Lippincott Williams & Wilkins|isbn=978-1-60547-433-5|pages=226}}</ref>

The term also has two other, conflicting meanings. In [[titration]], the titer is the ratio of actual to nominal concentration of a titrant, e.g. a titer of 0.5 would require 1/0.5 = 2 times more titrant than nominal. This is to compensate for possible degradation of the titrant solution. Second, in textile engineering, titre is also a synonym for [[linear density]].

==Etymology==
Titer has the same origin as the word "title", from the French word ''[[wikt:titre|titre]]'', meaning "title" but referring to the documented purity of a substance, often [[gold]] or [[silver]]. This comes from the [[Latin]] word ''[[wikt:titulus|titulus]]'', also meaning "title".

==Examples==
=== Antibody titer ===
An '''antibody titer''' is a measurement of how much [[antibody]] an organism has produced that recognizes a particular [[epitope]]. It is conventionally expressed as the inverse of the greatest dilution level that still gives a positive result on some test. [[ELISA]] is a common means of determining antibody titers. For example, the [[Coombs test|indirect Coombs test]] detects the presence of anti-Rh antibodies in a pregnant woman's [[blood serum]]. A patient might be reported to have an "indirect Coombs titer" of 16. This means that the patient's serum gives a positive indirect Coombs test at any dilution down to 1/16 (1 part serum to 15 parts diluent). At greater dilutions the indirect Coombs test is negative. If a few weeks later the same patient had an indirect Coombs titer of 32 (1/32 dilution which is 1 part serum to 31 parts diluent), this would mean that she was making ''more'' anti-Rh antibody, since it took a greater dilution to abolish the positive test.

Many traditional serological tests such as [[hemagglutination]] or [[complement fixation]] employ this principle. Such tests can typically be read visually, which makes them fast, cost-effective, and able to be deployed in a wide variety of laboratory environments. The interpretation of any serological titer result is guided by [[reference range|reference values]] that are specific to the [[antigen]] or [[antibody]] in question, so a titer of 1:32 may be below the cut-off for one test but above for another.

=== Other examples === 
A '''viral titer''' is the lowest concentration of a [[virus]] that still infects cells. To determine the titer, several dilutions are prepared, such as 10<sup>−1</sup>, 10<sup>−2</sup>, 10<sup>−3</sup>, ... 10<sup>−8</sup>.<ref name="KaplittLoewy1995"/>

The titer of a [[fat]] is the temperature, in degrees Celsius, at which it solidifies.<ref name="O'Brien2008">{{cite book|author=Richard D. O'Brien|title=Fats and oils: formulating and processing for applications|url=https://books.google.com/books?id=3wpHj3mvra8C&pg=PA207|access-date=18 March 2012|date=5 December 2008|publisher=CRC Press|isbn=978-1-4200-6166-6|pages=207}}</ref> The higher the titer, the harder the fat. This titer is used in determining whether an animal fat is considered [[tallow]] (titer higher than 40 °C) or a [[Yellow grease|grease]] (titer below 40 °C).<ref name="vanGerpen">{{cite book
  | last = van Gerpen
  | first = Jon Harlan |author2=Rudy Pruszko |author3=Davis Clements |author4=Gerhard Knothe |author5=Brent Shanks
  | title = Building a Successful Biodiesel Business
  | edition = 2nd illustrated
  | year = 2006
  | page = 93
  | publisher = Biodiesel Basics
  | isbn = 0-9786349-0-X
  | url = https://books.google.com/books?id=oN5b19Snx6wC
  | access-date = 2009-07-11
}}</ref>

==See also==
* [[Serology]]
* [[Titration]]
* [[W/v]]
* [[Mg%]]
* [[Virus quantification]]
* [[Viral burden|Viral titer]]

==References==
{{Reflist}}

[[Category:Chemical pathology]]
[[Category:Titration]]
[[Category:Immunology]]
[[Category:Immunologic tests]]