Due to its small size, intracellular habitat, and inability to properly take up many histological stains, diagnosis of "C. cayetanensis" can be very difficult. Four methods have thus far been established for positive diagnosis of the protozoan: microscopic detection in stool samples of oocysts; recovering oocysts in intestinal fluid/small bowel biopsy specimens; demonstration of oocyst sporulation; and amplification by polymerase chain reaction (PCR) of "C. cayetanensis" DNA. Since detection is so hard, one negative result should not discount the possibility of "C. cayetanensis": tests involving fresh stool samples over the next few days should also be considered.