The Labsystems Diagnostics Neonatal hTSH FEIA Plus is a fluorometric enzyme immunoassay designed for the quantitative determination of human thyroid-stimulating hormone (hTSH) in dried blood spot samples. It serves as a primary screening test for congenital hypothyroidism (CH) in newborns, enabling early diagnosis and timely intervention to prevent developmental complications. The assay elutes hTSH from dried blood disks and forms a specific sandwich complex between two antibodies—one immobilized on the solid phase and another labeled with horseradish peroxidase (HRP). The resulting fluorescence signal is directly proportional to the hTSH concentration, ensuring reliable and reproducible results.