A substance or reactant intended to be used together with a parent IVD to perform a specific function in an assay intended to be used in screening a clinical specimen for one or more congenital or metabolic disorders of the newborn. The test typically utilizes whole blood neonate specimens dried on filter paper, and the range of analytes detected may include neonatal thyroxine (neonatal T4), neonatal thyroid stimulating hormone (neonatal TSH), 17-hydroxyprogesterone, immunoreactive trypsinogen, various enzymes and/or amino acids, as indicators of congenital hypothyroidism, adrenal hyperplasia, cystic fibrosis, or other metabolic disorders.