Definition of reagin in US English:



  • 1The antibody which is involved in allergic reactions, causing the release of histamine when it combines with antigen in tissue, and capable of producing sensitivity to the antigen when introduced into the skin of a normal individual.

    • ‘An infant born to a seroreactive mother should be evaluated with a quantitative non-treponemal serologic test (e.g., rapid plasma reagin or VDRL).’
    • ‘The results of a VDRL test and rapid plasma reagin were negative.’
    • ‘The mother was O Rh-positive, antibody screen negative, rapid plasma reagin nonreactive, hepatitis B surface antigen negative.’
    • ‘An 18-year-old woman presented for her first prenatal visit at 31 weeks' gestation, at which time she was reactive for rapid plasmin reagin and had a 2 + fluorescent treponemal antibody.’
    • ‘Blood work, including rapid plasma reagin for syphilis and heavy metal screening, had been reported as normal.’
    1. 1.1 The substance in the blood which is responsible for a positive response to the Wassermann test.
      as modifier ‘a reagin test’
      count noun ‘reagins are measured by either complement fixation or flocculation tests’
      • ‘The patient's angiotensin-converting enzyme level was slightly elevated, and the rapid plasma reagin test was nonreactive.’
      • ‘This reaction is the basis of traditional nontreponemal tests such as the VDRL test and rapid plasma reagin test.’
      • ‘These tests used either complement fixation or flocculation techniques (Venereal Disease Research Laboratory [VDRL], rapid plasma reagin test, and automated reagin test).’
      • ‘The rapid plasmin reagin test was negative.’
      • ‘Even without a confirmatory rapid plasma reagin test or darkfield examination of the gummatous discharge, the diagnosis of secondary syphilis was obvious.’


Early 20th century: coined in German from reagieren ‘react’.