2) purgation with examination of three or more passages and 3) sigmoidoscopy with examination of aspirated materials if amebiasis is suspected. Since sigmoidoscopy reveals only a few inches of the colon and permits recovery of such small amounts of material, it should seldom be the sole method used. OTHER TYPES OF SPECIMENS For diagnosis of infections caused by certain species of intestinal parasites, materials other than feces will be received for examination. These materials should be examined as described under the heading "Other Specimens" in the section Methods of Examinations and in the following paragraphs. ASPIRATED MATERIAL Material aspirated from lesions is more often obtained in suspected cases of amebiasis than in other parasitic infections. It should be examined for the presence of trophozoites directly in wet mounts, using saline or temporary stains such as Quensel's or buffered methylene blue, or cultured (as previously described). If trophozoites or questionable structures are found, permanent stained slides of either fresh or PVA-fixed material should also be prepared. ANAL SWABS For the diagnosis of enterobiasis, anal swabs are received, usually cellulose-tape slide preparations or Vaseline-paraffin swabs. Refer to the section on Miscellaneous Procedures. URINE, VAGINAL SWABS, DUODENAL DRAINAGE MATERIAL, AND SPUTUM The handling of urine, vaginal swabs, duodenal drainage material and sputum has been discussed in the previous section and depends in part on the organism to be searched for. Selecting a technique for these body materials is not so much a problem as collecting and handling the specimen before examination. In all cases, the specimens should be examined as soon as possible, put into tubes of culture media, or preserved in appropriate solutions: Formalin for urine or sputum to be examined for helminth eggs, or PVA-fixative for urine, sputum, vaginal material or urethral exudate to be examined for protozoa. Preservatives may also be used for duodenal drainage or aspirates to be examined for Giardia. As stated previously, material obtained for the diagnosis of Trichomonas vaginalis should be examined by wet mount, cultivation, or both, rather than by stained smear. PROCEDURES FOR POSTTREATMENT SPECIMENS Disappearance of symptoms in a patient with a parasitic infection is not sufficient evidence of a "cure." Posttreatment specimens should be examined to determine the effectiveness of therapy. With most drugs used to treat patients with protozoan infections, organisms may not be found shortly after therapy even though the infection has not been eradicated. Thus, unless symptoms reappear earlier, the first posttreatment specimen should be collected approximately 4 weeks after therapy. Additional examinations after 3 and 6 months are advisable to detect later relapses. In helminth infections, posttreatment examinations may be made after 1 to 2 weeks. Persons who have been treated for Taenia infections should be checked 2 to 3 months later. The specimens should be collected in the same manner as for the initial diagnosis, that is, three normally passed specimens should be collected at 2- to 3-day intervals. In some cases, the specimens may be more conveniently and economically collected at the patient's home and shipped to the laboratory in Formalin (or MIF) and PVAfixative. The patient can be given three collection kits and instructed to submit specimens on specified dates. The specimens should be examined as described previously for normally passed feces. Posttreatment follow-up for enterobiasis should be made by examining anal swabs. Some workers recommend that the patient be examined for 7 days following completion of therapy and then periodically for 1 month. For practical purposes, three consecutive daily swabs might be examined 7 to 10 days after therapy and at weekly intervals for 3 weeks. If swabs become positive after being negative for a month, the patient has probably reacquired the parasite. REPORTING RESULTS All parasites found, both pathogenic and nonpathogenic species, should be reported by their scientific names. All helminths are considered pathogenic or potentially so, but certain intestinal protozoa are commensals or nonpathogens. Although commensals have no clinical significance, they do indicate that the patient has ingested material contaminated with feces. In persons harboring amebae, multiple infections have been found more frequently than can be accounted for by chance association (Boughton and Byrd, 1938; Eyles et al., 1953). Finding a nonpathogenic species, therefore, increases the likelihood that the individual may be infected with a pathogen. Additional specimens should be examined. In certain situations it might be advisable to identify the protozoa reported as pathogenic or nonpathogenic species. Occasionally protozoa, especially amebae, cannot be specifically identified. In these cases, an equivocal result should not be reported lest it be misinterpreted. A report of "organisms resembling E. histolytica," for example, may be interpreted as final identification of this pathogen and may lead to needless treatment of the patient. Vague reports of "amebae found" may also be accepted as indicating the presence of E. histolytica. If species identification cannot be made, "unidentified amebae found," "unidentified flagellates found," or "unidentified nematode (or trematode, cestode or helminth) egg (or larva) found" should be reported. Additional specimens should be examined. Although stages of helminths (eggs or larvae) are usually reported, stages of protozoa need not be reported. If cysts are found in the stool, trophozoites must be present in the intestinal tract. If no organisms are found, the specimen should be reported as "no parasites found (NPF)” and not as "negative." If additional laboratory procedures had been used or if some other person had examined the specimens, organisms might possibly have been found. |