This invention comprises nucleic acid ligand for use as a diagnostic reagent
for detecting the presence or absence of a target molecule in a sample, and a diagnostic
reagent to measure the amount of a target molecule in a sample. In a preferred
embodiment the nucleic acid ligands are identified by the method of the invention
referred to as the Systematic Evolution of Ligands by EXponential enrichment (SELEX),
wherein a candidate mixture of nucleic acids are iteratively enriched in high affinity
nucleic acids and amplified by further partitioning.