Giemsa stain
The preferable method for diagnosis of "P. malariae" is through the examination of peripheral blood films stained with Giemsa stain. PCR techniques are also commonly used for diagnoses confirmation as well as to separate mixed "Plasmodium" infections. Even with these techniques, however, it may still be impossible to differentiate infections, as is the case in areas of South America where humans and monkeys coexist and "P. malariae" and "P. brasilianum" are not easily distinguishable.