Evaluation of igg avidity test in primary toxoplasma gondii infection among pregnant women

الملخص EN

Background : The interpretational complexity of serological tests is a huge barrier in the diagnosis of toxoplasmosis in pregnant women.

Transferring of the parasite from mother to fetus is absolutely dependant on the time of acquisition of infection ; prior or post of pregnancy.

Methodology : IgG avidity test was assessed in solving this problematic issue.

Seventy two Toxo-latex positive serum samples of pregnant women were collected from different public and private gynecological clinics and laboratories within the city of Taiz, Yemen for the period from September 2005 to September 2007.

They were followed-up for their IgM, IgG and IgG avidity values along the full course of pregnancy.

Results : Primarily, 16 / 72 serum samples (22.2 %) had exhibited an IgM + IgG + serological profile during the first trimester of pregnancy.

These 16 samples showed different serological profile during the second and third trimesters of pregnancy.

Eleven out of these 16 samples were seroconverted into IgM - IgG + whereas the other 5 samples were not during the second and third trimesters of pregnancy.

The IgG avidity test results in the first trimester of pregnancy was high in 62.5 % of samples, whereas it was equivocal or low in 37.5 % of samples.

Many of the equivocal or low IgG avidity samples were developed into a high IgG avidity (81.25 %), whereas the others (18.75 %) were not during the second and third trimesters of pregnancy.

A strong correlation was found between the maturity of IgG avidity and the IgM seroconversion.

Conclusions and recommendations : This study elucidates the value of IgG avidity as a confirmatory test for old Toxoplasma infections that happened before pregnancy when the avidity was high.

However, this value was limited in confirming or excluding of recent Toxoplasma infections that occurred after pregnancy when the avidity was low or equivocal.