The necessity of confirmatory testing in serodiagnosis of toxoplasmosis in iran.

  • Mehrzad Saraei Dept. of Medical Parasitology and Mycology, School of Medicine, Qazvin University of Medical Sciences, Qazvin, Iran AND Cellular and Molecular Research Center, Qazvin University of Medical Sciences, Qazvin, Iran AND Reference Laboratory, Qazvin University of Medical Sciences, Qazvin, Iran.
  • Seyedeh Zeinab Fattahi Reference Laboratory, Qazvin University of Medical Sciences, Qazvin, Iran.
  • Mojtaba Shahnazi Dept. of Medical Parasitology and Mycology, School of Medicine, Qazvin University of Medical Sciences, Qazvin, Iran.
  • Afshin Afshari Dept. of Microbiology and Immunology, School of Medicine, Qazvin University of Medical Sciences, Qazvin, Iran.
  • Safar Ali Alizadeh Dept. of Pathobiology, School of Public Health and Institute of Public Health Research, Tehran University of Medical Sciences, Tehran, Iran.
  • Hassan Jahanihashemi Dept. of Community Medicine, School of Medicine, Qazvin University of Medical Sciences, Qazvin, Iran.
Keywords: ELISA, IgG Avidity, Iran, Toxoplasma gondii


 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 cor-relation 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 ºC for futures use. Sero-logic 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 pre-sented as semi quantitative for IgG, IgM and IgA ELISA, and Relative Avidity In-dex 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). Conclusion: The study strongly highlights the necessity of confirmatory testing in differential diagnosis of acute and chronic toxoplasmosis in Iran.


Assmar M, Amirkhani A, Piazak N, Hovanesi-an A, Kooloobandi A, Etessami R. [Toxo-plasmosis in Iran. Results of a seroepidemi-ological study]. Bull Soc Pathol Exot. 1997; 90(1): 19-21.

Montoya JG, Boothroyd JC, Kovacs JA. Toxo-plasma gondii. In: Mandell GL, Bennett JE, Dol-in R, editors. Mandell, Douglas, and Bennett's principles and practice of infectious diseases. 7th ed. Philadelphia: Churchill Livigstone; 2010. P. 3495-526.

Fernandes RC, Vasconcellos VP, Araújo LC, Medina-Acosta E. Vertical transmission of HIV and Toxoplasma by reactivation in a chron-ically infected woman. Braz J Infect Dis. 2009; 13(1): 70-1.

Remington JS, Thulliez P, Montoya JG. Recent developments for diagnosis of toxoplasmosis. J Clin Microbiol. 2004; 42(3): 941–5.

Suzuki LA, Rocha RJ, Rossi CL. Evaluation of serological markers for the immunodiagnosis of acute acquired toxoplasmosis. J Med Micro-biol. 2001; 50(1): 62-70.

Lappalainen M, Hedman K. Serodiagnosis of toxoplasmosis. The impact of measurement of IgG avidity. Ann Ist Super Sanita. 2004; 40(1): 81-8.

Ashburn D, Joss AW, Pennington TH, Ho-Yen DO. Do IgA, IgE, and IgG avidity tests have any value in the diagnosis of Toxoplasma infection in pregnancy? J Clin Pathol. 1998; 51(4): 312–5.

Bobic B, Sibalic D, Djurkovic-Djakovic O. High levels of IgM antibodies specific for Toxo-plasma gondii in pregnancy 12 years after primary Toxoplasma infection. Gynecol Obstet Invest. 1991; 31(3): 182–4.

Faure AK, Fricker-Hidalgo H, Pelloux H, Bost-Bru C, Goullier-Fleuret A, Ambroise-Thomas P. Lack of value of specific IgA detec-tion in the postnatal diagnosis of congenital toxoplasmosis. J Clin Lab Anal. 1999; 13(1): 27-30.

Kodym P, Machala L, Rohácová H, Sirocká B, Malý M. Evaluation of a commercial IgE ELI-SA in comparison with IgA and IgM ELISAs, IgG avidity assay and complement fixation for the diagnosis of acute toxoplasmosis. Clin Mi-crobiol Infect. 2007; 13(1): 40-7.

Montoya JG, Huffman HB, Remington JS. Evaluation of the immunoglobulin G avidity test for diagnosis of toxoplasmic lymphade-nopathy. J Clin Microbiol. 2004; 42(1): 4627-31.

Nascimento FS, Suzuki LA, Rossi CL. Assess-ment of the value of detecting specific IgA an-tibodies for the diagnosis of a recently acquired primary Toxoplasma infection. Prenat Diagn. 2008; 28(8): 749-52.

Hedman K, Lappalainen M, Seppäiä I, Mäkelä O. Recent primary Toxoplasma infection indi-cated by a low avidity of specific IgG. J Infect Dis. 1989; 159(4): 736-40.

Candolfi E, Pastor R, Huber R, Filisetti D, Vil-lard O. IgG avidity assay firms up the diagnosis of acute toxoplasmosis on the first serum sam-ple in immunocompetent pregnant women. Diagn Microbiol Infect Dis. 2007; 58(1): 83–88.

Montoya JG, Liesenfeld O, Kinney S, Press C, Remington JS. VIDAS test for avidity of Toxo-plasma-specific immunoglobulin G for con-firmatory testing of pregnant women. J Clin Microbiol. 2002; 40(7): 2504–8.

Jenum PA, Stray-Pedersen B, Gundersen AG. Improved diagnosis of primary Toxoplasma gondii infection in early pregnancy by determi-nation of anti-Toxoplasma immunoglobulin G avidity. J Clin Microbiol. 1997; 35(8): 1972–7.

Lefever-Pettazzoni M, Le Cam S, Wallon M, Peyron F. Delayed maturation of immuno-globulin G avidity: implication for the diagnosis of toxoplasmosis in pregnant women. Eur J Clin Microbiol Infect Dis. 2006; 25(11): 687-93.

Auer H, Vander-Möse A, Picher O, Walochnik J, Aspöck H. Clinical and diagnostic relevance of the Toxoplasma IgG avidity test in the sero-logical surveillance of pregnant women in Aus-tria. Parasitol Res. 2000; 86(12): 965-70.

Tanyuksel M, Guney C, Araz E, Saracli MA, Doganci L. Performance of the immunoglobu-lin G avidity and enzyme immunoassay IgG/IgM screening tests for differentiation of the clinical spectrum of toxoplasmosis. J Mi-crobiol. 2004; 42(3): 211-5.

Igbal J, Khalid N. Detection of acute Toxo-plasma gondii infection in early pregnancy by IgG avidity and PCR analysis. J Med Microbiol. 2007; 56(Pt 11): 1495-9.

Liesenfeld O, Montoya JG, Kinney S, Press C, Remington JS. Effect of testing for IgG avidity in the diagnosis of Toxoplasma gondii infection in pregnant women: experience in a US reference laboratory. J Infect Dis. 2001; 183(8): 1248-53.

Lachaud L, Calas O, Picot MC, Albaba S, Bourgeois N, Pratlong F. Value of 2 IgG avid-ity commercial tests used alone or in associa-tion to date toxoplasmosis contamination. Di-agn Microbiol Infect Dis. 2009; 64(3): 267-74.

Yamada H, Nishikawa A, Yamamoto T, Mizue Y, Yamada T, Morizane M, Tairaku S, Nishihi-ra J. Prospective study of congenital toxo-plasmosis screening with use of IgG avidity and multiplex nested PCR methods. J Clin Mi-crobiol. 2011; 49(7): 2552-6.

Meroni V, Genco F, Tinelli C, Lanzarini P, Bollani L, Stronati M, et al. Spiramycin treat-ment of Toxoplasma gondii infection in pregnant women impairs the production and the avidity maturation of T. gondii-specific immunoglobu-lin G antibodies. Clinical and Vaccine Immu-nology. 2009; 16(10): 1517–20.

Liesenfeld O, Press C, Montoya JG, Gill R, Isaac-Renton JL, Hedman K, et al. False-posi-tive results in immunoglobulin M (IgM) Toxo-plasma antibody tests and importance of con-firmatory testing: the Platelia Toxo IgM test. J Clin Microbiol. 1997; 35(1): 174-8.

Rahbari AH, Keshavarz H, Shojaee S, Mohe-bali M, Rezaeian M. IgG avidity ELISA test for diagnosis of acute toxoplasmosis in humans. Korean J Parasitol. 2012 ; 50(2): 99-102.

Reis MM, Tessaro MM, D'Azevedo PA. Toxo-plasma-IgM and IgG-avidity in single samples from areas with a high infection rate can deter-mine the risk of mother-to-child transmission. Rev Inst Med Trop Sao Paulo. 2006; 48(2): 93-8.

Leite M, Siciliano S, Rocha LS, Justa MT, César KR, Granato CF. Correlation between specific IgM levels and percentage IgG-class antibody avidity to Toxoplasma gondii. Rev Inst Med Trop Sao Paulo. 2008; 50(4): 237-42.

Bobic B, Klun I, Vujanic M, Nikolic A, Ivovic V, Zivkovic T, et al. Comparative evaluation of three commercial Toxoplasma-specific IgG anti-body avidity tests and significance in different clinical settings. J Med Microbiol. 2009 ; 58(Pt 3): 358-64.

Paul M. Immunoglobulin G avidity in diagno-sis of toxoplasmic lymphadenopathy and ocu-lar toxoplasmosis. Clin Diagn Lab Immunol. 1999; 6: 514-8.

Suresh S, Nor-Masniwati S, Nor-Idahriani MN, Wan-Hazabbah WH, Zeehaida M, Zunaina E. Serological IgG avidity test for ocular toxo-plasmosis. Clin Ophthalmol. 2012; 6(4): 147-50.

Kaul R, Chen P, Binder SR. Detection of im-munoglobulin M antibodies specific for Toxo-plasma gondii with increased selectivity for re- cently acquired infections. J Clin Microbiol. 2004; 42(12): 5705-9.

Rossi CL. A simple, rapid enzyme-linked im-munosorbent assay for evaluating immuno-globin G antibody avidity in toxoplasmosis. Di-agn Microbiol Infect Dis. 1998; 30(1): 25-30.

Hashemi HJ, Saraei M. Seroprevalence of Toxo-plasma gondii in unmarried women in Qazvin,

Islamic Republic of Iran. East Mediterr Health J. 2010; 16(1): 24-8.

Hajsoleimani F, Ataeian A, Nourian A, Mazloomzadeh S. Seroprevalence of Toxo-plasma gondii in Pregnant Women and Bioas-say of IgM Positive Cases in Zanjan, North-west of Iran. Iranian J Parasitol. 2012; 7(2): 82-6.

How to Cite
Saraei M, Fattahi SZ, Shahnazi M, Afshari A, Alizadeh SA, Jahanihashemi H. The necessity of confirmatory testing in serodiagnosis of toxoplasmosis in iran. IJPA. 8(4):608-16.