Blastocystis Hominis is diagnosed using microscopy on a stool sample. The CDC recommends that samples be concentrated and at least three separate samples should be taken before a negative result is confirmed. The two most common methods for preparing slides are a wet mount and a trichrome stain. In the wet mount Blastocystis Hominis is stained with iodine and appears as a large vacuole in the middle of many small nuclei, though it may be difficult to see. In the trichrome stain, the parasite is stained with trichrome giving the large central body a gray or green appearance and the cytoplasm elements a dark red color
Even though the pathogenicity of Blastocystis Hominis remains controversial, anti-protozoan drugs have been used to treat individuals in whom the parasite is found. The most widely used treatment option is the chemotherapeutic drug Metronidazole which, while effective in some individuals, shows signs of resistance by B. hominis or limited effectiveness in others. At least one group of researchers has also used the drug combination Trimethoprim/Sulfamethoxazole (TMP/SMX) with similar effects.[16] More recently, Nitazoxanide has been with much more positive effects, with 86% of those treated with the drug effectively cured.