Abstract
Retrospective testing of neonatal Guthrie card blood spots for specific immunoglobulin M (IgM) can distinguish congenital toxoplasmosis from acquired toxoplasmosis. We determined whether storage temperature reduced IgM detection, using filter paper blood samples "spiked" with anti-Toxoplasma IgM. After 300 days, IgM detection deteriorated with storage at room temperature but not at temperatures of 4 degrees C or lower.