Editing Mantoux test (section)

==Two-step testing==
Some people who have been infected with TB may have a negative reaction when tested years after infection, as the immune system response may gradually wane. This initial skin test, though negative, may stimulate (boost) the body's ability to react to tuberculin in future tests. Thus, a positive reaction to a subsequent test may be misinterpreted as a new infection, when in fact it is the result of the boosted reaction to an old infection.<ref>{{Cite web|url=https://www.cdc.gov/tb/publications/factsheets/testing/skintesting.htm|title=Fact Sheets {{!}} Testing & Diagnosis {{!}} Fact Sheet - Tuberculin Skin Testing {{!}} TB {{!}} CDC|date=2018-12-11|website=www.cdc.gov|language=en-us|access-date=2019-05-29}}</ref>

Use of two-step testing is recommended for initial skin testing of adults who will be retested periodically (e.g., health care workers). This ensures any future positive tests can be interpreted as being caused by a new infection, rather than simply a reaction to an old infection.{{cn|date=May 2024}}
* The first test is read 48–72 hours after injection.
** If the first test is positive, consider the person infected.
** If the first test is negative, give a second test one to three weeks after the first injection.
* The second test is read 48–72 hours after injection.
** If the second test is positive, consider the person infected in the distant past.<ref>{{cite web | title=Information on Two-Step TB Skin Test | url=https://www.ccsf.edu/en/student-services/student-health-services/medical-service/tb-testing/_jcr_content/rightlinks/documentlink_0/file.res/Two-Step%20TB%20Skin%20Test.pdf | access-date=2017-03-13 | archive-date=2020-08-03 | archive-url=https://web.archive.org/web/20200803162920/https://www.ccsf.edu/en/student-services/student-health-services/medical-service/tb-testing/_jcr_content/rightlinks/documentlink_0/file.res/Two-Step%20TB%20Skin%20Test.pdf | url-status=dead }}</ref>
** If the second test is negative, consider the person uninfected.<ref>{{cite web | author=Office of Health and Human Services | title=Booster Phenomenon | url=http://www.mass.gov/?pageID=eohhs2terminal&L=7&L0=Home&L1=Provider&L2=Guidelines+and+Resources&L3=Guidelines+for+Clinical+Treatment&L4=Diseases+%26+Conditions&L5=Tuberculosis+Prevention+and+Control&L6=Screening+and+Testing&sid=Eeohhs2&b=terminalcontent&f=dph_cdc_p_tb_testing_booster+&csid=Eeohhs2 | access-date=2008-07-02}}</ref>

A person who is diagnosed as "infected in the distant past" on two-step testing is called a "tuberculin reactor".{{cn|date=May 2024}}

The US recommendation that prior BCG vaccination be ignored results in almost universal false diagnosis of tuberculosis infection in people who have had BCG (mostly foreign nationals).{{cn|date=May 2024}}