The diagnosis of toxoplasmosis using IgG avidity

Epidemiol Infect. 1994 Apr;112(2):399-408. doi: 10.1017/s0950268800057812.


Current methods to establish the duration of toxoplasma infection in pregnant women and for the diagnosis of toxoplasmosis in the neonate or HIV infected patient have significant limitations. We assessed the precision of a commercial ELISA for the detection of toxoplasma specific IgG and adapted the assay to measure avidity using an elution agent washing step. The sensitivity and specificity of the ELISA were 100 and 75% respectively and optimal measurement of avidity was achieved using 6 M urea as the elution agent. Toxoplasma lymphadenopathy of less than 3 months duration was associated with low avidity specific IgG but some discordant findings were recorded. Serial measurement of IgG avidity assisted the distinction between actively produced antibody in infants with congenital toxoplasmosis and passively acquired antibody of maternal origin in uninfected babies. There was no significant difference between avidity levels in HIV infected patients with or without cerebral toxoplasmosis.

Publication types

  • Comparative Study

MeSH terms

  • AIDS-Related Opportunistic Infections / blood
  • AIDS-Related Opportunistic Infections / diagnosis*
  • AIDS-Related Opportunistic Infections / epidemiology
  • Acute Disease
  • Adult
  • Animals
  • Antibodies, Protozoan / blood*
  • Antibody Affinity / immunology*
  • Child, Preschool
  • Chronic Disease
  • Coloring Agents
  • Diagnosis, Differential
  • Enzyme-Linked Immunosorbent Assay / methods*
  • Female
  • Humans
  • Immunity, Active
  • Immunity, Maternally-Acquired
  • Immunoglobulin G / blood*
  • Infant
  • Infant, Newborn
  • Latex Fixation Tests
  • Reproducibility of Results
  • Sensitivity and Specificity
  • Time Factors
  • Toxoplasma / immunology*
  • Toxoplasmosis, Cerebral / blood
  • Toxoplasmosis, Cerebral / diagnosis*
  • Toxoplasmosis, Cerebral / epidemiology
  • Toxoplasmosis, Congenital / blood
  • Toxoplasmosis, Congenital / diagnosis*
  • Toxoplasmosis, Congenital / epidemiology
  • Urea


  • Antibodies, Protozoan
  • Coloring Agents
  • Immunoglobulin G
  • Urea