Final answer:
A phlebotomist specializing in highly specialized testing is probably employed by a Reference laboratory, handling complex tests alongside other laboratory professionals.
Step-by-step explanation:
A phlebotomist working for an organization that performs highly specialized testing is most likely employed by a Reference laboratory. This type of facility is specifically designed to conduct complex and unique diagnostic tests that are not typically performed within a hospital or clinic setting. Phlebotomists are skilled professionals who specialize in the practice of drawing blood for tests, transfusions, donations, or research. In a reference laboratory, they may work alongside medical technologists and other laboratory professionals, using their expertise to ensure that blood samples are appropriately collected and processed for advanced testing procedures.