Examination of preserved stool specimens for parasites: lack of value of the direct wet mount

To review the appropriateness of standard reference procedures for diagnostic parasitology, we examined 2,206 stool specimens in our laboratory by direct wet mounting with saline and iodine, by saline and iodine wet mounting from Formalin-ethyl acetate concentrates, and by permanent staining with Wheatley's modified trichrome method (W.B. Wheatley, Am. J. Clin. Pathol. 21: 990-991, 1951). Parasites were detected in 98 stool specimens (4.4%). In all but three specimens, direct wet mounting with saline and iodine contributed little significant information to the result yet consumed substantial technical time. We recommend that with preserved feces a direct examination not be performed but that examination of both a concentrate and a permanent stain be routine.