title: Incidence of the prozone phenomenon in syphilis serology.
abstract: OBJECTIVE
  To determine the rate of the prozone phenomenon in our patient population.
  
  
  METHODS
  Sera from 4328 patients--3504 females (2065 pregnant, 1439 nonpregnant) and 824 males--were tested for syphilis by the rapid plasma reagin (RPR) test, and then rechecked with serial twofold dilutions of up to 16-fold to detect the prozone phenomenon. Chi-square analysis with Yates correction was used, with P < or = .05 considered significant.
  
  
  RESULTS
  The total positivity rate in females was 6% (213 patients); 13% (27) of the positive tests were false-positive reactions as confirmed by a negative anti-treponemal antibody test. Only one prozone reaction was detected, in serum from a male subject, but it was not missed on initial screening.
  
  
  CONCLUSIONS
  The rate of prozone phenomenon is very low (95% confidence interval 0-0.4%), and routine serial dilutions are not cost effective.
authors.affiliation: Department of Gynecology and Obstetrics, Emory University School of Medicine, Atlanta, Georgia.
authors.forename: M M
authors.initials: MM
authors.lastname: el-Zaatari
authors.forename: M G
authors.initials: MG
authors.lastname: Martens
authors.forename: G D
authors.initials: GD
authors.lastname: Anderson
mesh_terms: D016009:Chi-Square Distribution; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D015994:Incidence; D007201:Indicator Dilution Techniques; D008297:Male; D008403:Mass Screening; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000175:diagnosis*; D013587:Syphilis / Q000175:diagnosis*; D013588:Syphilis Serodiagnosis / Q000379:methods*