Masowe badania serologiczne noworodków w kierunku obecności swoistych przeciwciał IgA i IgM anty-Toxoplasma gondii we krwi obwodowej pobranej na bibułę*

Małgorzata Paul

Streszczenie
Introduction: The strategic approach for preventing congenital toxoplasmosis is strictly related to the incidence of primary Toxoplasma gondii infection during pregnancy in a studied population. The aims of the regional neonatal screening programme were to detemine (i) the prevalence of congenital T. gondii infection at birth in the Wielkopolska region, (ii) the value of the serological examination of filter-paper blood specimens collected at birth for the diagnosis of congenital toxoplasmosis, and (iii) the duration of T. gondii-specific immunoglobulin A and immunoglobulin M antibodies in infants, untreated prenatally. Materials and methods: The neonates born in the obstetric clinics of the University Hospital in Poznań and in the maternity wards of the 10 main district hospitals from the Wielkopolska Province were systematically screened for congenital T. gondii infection. Peripheral blood from newborns was collected by a low invasive heel-stick puncture, absorbed onto Guthrie cards and analysed for anti-T. gondii specific IgM (1996-1998) or both IgA and IgM antibodies (1998-2000). Non-commercial immunodiagnostic tests were based on ultrasonicated Tx12 antigen of T. gondii tachyzoites from in vitro culture and monoclonal antibody anti-SAG1. Results: From June 1996 to April 2000, 45, 169 filter-paper specimens from liveborn neonates were screened: 27,516 samples were tested for specific IgM and the next 17,653 Guthrie cards were analysed by the combined IgA/IgM assay, elaborated for the first time. The prevalence of anti-Toxoplasma IgM in filter-paper eluates at birth was 1 per 2,117 liveborn neonates (0.47/1,000) or 1 per 1,185 infants (0.84/1,000) born to seronegative women with a potential risk of primary T. gondii infection during pregnancy. For the joint detection of IgA and IgM, these values significantly increased to 1 per 929 neonates (1.08/1,000) and 1 per 520 pregnancies at risk (1.92/1,000) respectively, comparing to the seropositivity rate of 43.7% in the pregnant women population of the studied area. Conclusions: (i) The neonatal screening for anti-Toxoplasma IgA or IgM antibodies is a good sensitivity method for an early postnatal diagnosis of congenital toxoplasmosis in newborns untreated prenatally. (ii) In the absence of obligatory nation-wide screening during pregnancy followed by an early prenatal treatment, this valuable technique may be considered a preventive option in areas with a high seroprevalence of T. gondii infection.

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