Journal Article

A Rational Approach to the Stool Ova and Parasite Examination

John A. Branda, Tai-Yuan David Lin, Eric S. Rosenberg, Elkan F. Halpern and Mary Jane Ferraro

in Clinical Infectious Diseases

Published on behalf of Infectious Diseases Society of America

Volume 42, issue 7, pages 972-978
Published in print April 2006 | ISSN: 1058-4838
Published online April 2006 | e-ISSN: 1537-6591 | DOI:
A Rational Approach to the Stool Ova and Parasite Examination

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Background. Examination of multiple stool specimens per patient to rule out parasitic infection continues to be recommended in the literature. Attractive alternatives have been proposed, such as examination of a single specimen, but data to support their use have been inconclusive.

Methods. We reviewed the results of comprehensive stool ova and parasite examinations performed during a 1-year period to determine the incremental value of examining >1 specimen. Next, we implemented rejection criteria, allowing analysis of only a single specimen in most cases, and studied the impact of the change by reviewing data from a subsequent year.

Results. Prior to implementation of rejection criteria, 91% of parasites were detected in the first specimen submitted, although many clinical evaluations (72%) involved the submission of only 1 stool specimen. When at least 3 specimens were submitted, the sensitivity of examining the first in the series was 72%. Even the latter sensitivity provides negative predictive values of ∼98%, ∼97%, ∼95%, or ∼93% when the prevalence of parasites among those tested is 5%, 10%, 15%, or 20%, respectively. Examination of additional specimens after examination of the first specimen that yielded a positive finding revealed previously undetected parasites in only 10% of cases. After the application of rejection criteria, the parasite detection rate did not change significantly.

Conclusions. Comprehensive examination of a single stool specimen is sufficient for most patients, when the prevalence of infection among the tested population is up to 20%. Rational use of the stool ova and parasite examination relies on communication between clinician and laboratory, and retention of deferred specimens in case examination of additional specimens is clinically warranted.

Journal Article.  4238 words.  Illustrated.

Subjects: Infectious Diseases ; Immunology ; Public Health and Epidemiology ; Microbiology

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