The Need for Three Stool Specimens in Routine Laboratory Examinations for Intestinal Parasites

Abstract

SUMMARYThis study was designed to test whether three sequential stool specimens are necessary for reliable detection of intestinal parasites in routine laboratory examinations. There were 175 patients in whom a single species of intestinal parasite or ova was identified on at least one occasion when three stool specimens were examined over a period of 14 days from the first recorded specimen. Examination of a first stool specimen detected parasites and/or ova in 102/175 patients (58.3%); examination of a second specimen identified an additional 36 positive patients (20.6%) and examination of a third specimen yielded a final 37 previously undetected patients (21.1%).These findings indicate that at least three stool specimens should be examined to confirm the presence of intestinal parasites. Even with such practice, it is not possible to guarantee that there is no infestation, but examination of fewer specimens would run a definite risk of false negative results.

Evaluation of the Performance of the Novodiag® Stool Parasites Assay for the Detection of Intestinal Protozoa and Microsporidia

“…In addition, it is difficult to know whether it is still necessary to repeat parasite stool examination when performing the NSP assay as recommended for microscopic methods due to their low overall sensitivity and the intermittent shedding of some parasites [ 1 ]. The need to repeat examinations is controversial among populations in which the prevalence of infections is low [ 20 ].…”

“…However, this approach has some limitations because it is labour-intensive and requires a high level of skill for optimal examination, which remains a major challenge due to the low number of positive samples received annually for many laboratories in high-income countries. Microscopic methods may produce poor analytical sensitivity, and it is therefore usually accepted that three consecutive samples collected over a few days are necessary to increase its sensitivity [ 1 ]. Finally, microscopic examination is also ineffective in differentiating pathogenic and non-pathogenic members of some species complex of protozoans such as Entamoeba , and it is unable to diagnose microsporidia or coccidia (Cryptosporidia, Cyclospora cayetanensis , Cystoisospora belli ) without specific staining.…”

Hook Worm Infestation in a Neonate

“…Hook worms attach to small intestine, damage the mucosae/submucosae and rupture the capillaries to cause protein and blood loss, severity of which depends on the worm burden and loss of up to 250 mL/day have been documented (5). Diagnosis is based on clinical feature (anemia) and stool examination for ova and cyst, the sensitivity of which varies from 58.5% to 95% (when stool is examined thrice) (6). Eosinophilia in our patient further supported the diagnosis.…”