Using a spiked library prepared with HEK293 cells that express human CD19 at a comparable level to lymphoma cell lines and secretes a functional CD19xCD3 BiTE, we characterized the analytical performance, including screening efficiency, and demonstrated the single cell platform is capable of isolating ≥1 copies of a rare functional clone (0.008% abundance) with 95% confidence in a single run. The gene discussed is CD19; the disease is lymphoma.