title: In utero and at birth diagnosis of congenital toxoplasmosis: use of likelihood ratios for clinical management.
abstract: BACKGROUND
  The results of the ante- and neonatal diagnostic tests for congenital toxoplasmosis influence the decision to treat the newborn immediately after birth. Here, we estimate the positive and negative likelihood ratios (LRs) and the probabilities of congenital infection according to PCR and IgM-IgA tests results.
  
  
  METHODS
  The study concerned 767 children born between 1996 and 2002 and followed-up for 1-year at Croix-Rousse hospital, Lyon, France. The LRs and the post-test probabilities were estimated conditionally on gestational age at maternal infection using a logistic regression approach.
  
  
  RESULTS
  For the PCR and the IgM-IgA tests, the positive LRs were high. In children with one positive test when only one test was done, the probability of infection reached 90% when the maternal infection occurred at 18-weeks gestation or later. This probability was close to 100% when the 2 tests were positive, whatever the gestational age. The negative LRs of the 2 tests moved closer to 0 at later gestational ages. However, when the tests were negative, the probability of infection remained greater or equal to 10%, except in early maternal infection. When the 2 tests were discordant, the probability of infection was about 50% in early maternal infection.
  
  
  CONCLUSIONS
  Providing reliable probabilities of congenital infection, the PCR and IgM-IgA tests guide clinical management and counseling of parents.
authors: Hospices Civils de Lyon, Service de Biostatistique, Lyon, France. muriel.rabilloud@chu-lyon.fr
authors: Muriel
authors: M
authors: Rabilloud
authors: Martine
authors: M
authors: Wallon
authors: François
authors: F
authors: Peyron
mesh_terms: D000913:Antibodies, Protozoan / Q000097:blood; D016054:DNA, Protozoan / Q000235:genetics; D005260:Female; D005602:France; D006801:Humans; D007070:Immunoglobulin A / Q000097:blood; D007075:Immunoglobulin M / Q000097:blood; D007231:Infant, Newborn; D008297:Male; D016133:Polymerase Chain Reaction; D011237:Predictive Value of Tests; D011247:Pregnancy; D011296:Prenatal Diagnosis / Q000379:methods*; D014122:Toxoplasma / Q000235:genetics* / Q000276:immunology*; D014125:Toxoplasmosis, Congenital / Q000175:diagnosis* / Q000188:drug therapy*
chemical_list: D000913:Antibodies, Protozoan; D016054:DNA, Protozoan; D007070:Immunoglobulin A; D007075:Immunoglobulin M