Absence of significant differences in intestinal parasite prevalence estimates after examination of either one or two stool specimens.

The authors undertook a retrospective search of intestinal parasite laboratory records obtained from 200 consecutive-day pairs of stool specimens to compare prevalence estimates from the first and second stool examinations. The laboratory results had previously been recorded as part of a screening program offered to Southeast Asian refugees arriving in Montréal, Québec, Canada, between July 1982 and February 1983. No statistically significant differences in either overall prevalences or parasite-specific prevalences were observed. This suggests that, at least in some population-based situations, single stool examinations provide estimates of intestinal parasite prevalence which are as valid as those from the routine examination of two consecutive-day specimens. Blinded studies must be undertaken to accurately assess the true value of multiple specimen submission in epidemiologic studies.