IgG Avidity in Samples Collected on Filter Paper: Importance of The Early Diagnosis of Congenital Toxoplasmosis

Area of Science:

• Neonatal immunology
• Infectious disease diagnostics
• Clinical chemistry

Background:

• Congenital toxoplasmosis poses a significant risk to newborns.
• Early diagnosis is crucial for effective management and prevention of long-term complications.
• Standard diagnostic methods can be challenging to implement in routine newborn screening programs.

Purpose of the Study:

• To standardize and evaluate the immunoglobulin G (IgG) antibody avidity test using newborn filter paper blood samples.
• To assess the feasibility of implementing this test in existing newborn screening programs.
• To determine the reliability of the filter paper method compared to traditional serum analysis.

Main Methods:

• Collected blood samples from newborns via heel prick onto filter paper, concurrently with routine screening.
• Performed immunoglobulin M (IgM) and IgG enzyme-linked immunosorbent assays (ELISA) on all samples.
• Utilized IgG avidity testing on both serum and filter paper samples, classifying results using the Rahbari protocol.

Main Results:

• Out of 177 samples, 17 were collected in duplicate for validation.
• One duplicate sample (5.88%) showed low IgG avidity, suggesting potential congenital infection.
• High agreement (94.12%) was observed between IgG avidity results from serum and filter paper samples.

Conclusions:

• The IgG antibody avidity test on filter paper is a reliable method for diagnosing congenital toxoplasmosis.
• This method demonstrates high concordance with traditional serum testing.
• The filter paper approach offers a viable alternative for implementation in newborn screening programs.