SOMAmer^® (Slow Off-rate Modified Aptamer) Reagents are identified via the SELEX process against epitopes on a single target protein in buffer. While this shape recognition is highly specific, some proteins share structural and/or functional properties, and thus could be bound by a SOMAmer Reagent originally selected against another protein. In order to test the specificity of SOMAmer Reagents used in the SomaScan Assay for their respective initial target proteins, we perform a variety of characterization steps. These steps include: all affinity reagents (antibodies, traditional aptamers, etc.) are subject to specificity issues. Recognizing how critical the accuracy of the SomaScan Assay is for both research and clinical purposes, SomaLogic is committed to regular assessment of SOMAmer specificity, and to transparency in communicating the results of those ongoing efforts.