title: The necessity of confirmatory testing in serodiagnosis of toxoplasmosis in iran.
abstract: BACKGROUND
  Toxoplasma specific IgM antibodies; the common serologic marker in diagnosis of acute toxoplasmosis has its own limitations. Confirmatory testing with other markers, introduced as a complementary tool in distinguish acute and chronic infections is unusual in Iran. In the present study, we investigated the correlation between the results of IgM ELISA, IgA ELISA, and IgG avidity tests in the diagnosis of toxoplasmosis to demonstrate the necessity of confirmatory testing in serodiagnosis of infection in the country.
  
  
  METHODS
  A total of 107 positive Toxoplasma IgG and IgM sera were obtained from patients referred to private laboratories and stored at -20 °C for futures use. Serologic tests were set up in duplicate to analyze the serum levels of IgG, IgM, IgA, and IgG avidity antibodies using commercial ELISA kits. The results were presented as semi quantitative for IgG, IgM and IgA ELISA, and Relative Avidity Index in percentage for IgG avidity test. Pearson's correlation coefficient (rp) was applied to analyze the data.
  
  
  RESULTS
  Of 107 serum samples, T. gondii specific IgM and IgA antibodies were positive in 67.3% and 53.3%, respectively. Besides, 29.9% of the sera displayed low avidity for IgG antibodies. The rp was - 0.572 (P<0.01) between the IgG avidity and IgM ELISA, - 0.364 between the IgG avidity and IgA ELISA (P<0.01), and 0.564 between the IgM and IgA ELISA (P<0.01).
  
  
  CONCLUSIONS
  The study strongly highlights the necessity of confirmatory testing in differential diagnosis of acute and chronic toxoplasmosis in Iran.
authors.affiliation: Dept. of Medical Parasitology and Mycology, School of Medicine, Qazvin University of Medical Sciences, Qazvin, Iran ; Cellular and Molecular Research Center, Qazvin University of Medical Sciences, Qazvin, Iran ; Reference Laboratory, Qazvin University of Medical Sciences, Qazvin, Iran.
authors.forename: Mehrzad
authors.initials: M
authors.lastname: Saraei
authors.affiliation: Reference Laboratory, Qazvin University of Medical Sciences, Qazvin, Iran.
authors.forename: Seyedeh Zeinab
authors.initials: SZ
authors.lastname: Fattahi
authors.affiliation: Dept. of Medical Parasitology and Mycology, School of Medicine, Qazvin University of Medical Sciences, Qazvin, Iran.
authors.forename: Mojtaba
authors.initials: M
authors.lastname: Shahnazi
authors.affiliation: Dept. of Microbiology and Immunology, School of Medicine, Qazvin University of Medical Sciences, Qazvin, Iran.
authors.forename: Afshin
authors.initials: A
authors.lastname: Afshari
authors.affiliation: Dept. of Pathobiology, School of Public Health and Institute of Public Health Research, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Safar Ali
authors.initials: SA
authors.lastname: Alizadeh
authors.affiliation: Dept. of Community Medicine, School of Medicine, Qazvin University of Medical Sciences, Qazvin, Iran.
authors.forename: Hassan
authors.initials: H
authors.lastname: Jahanihashemi
keywords: ELISA; IgG Avidity; Iran; Toxoplasma gondii