The trichrome-stained smear as a screening method for intestinal parasites: evaluation in a San Francisco Bay Area population.

The trichrome-stained smear and the formalin-ether concentrate were compared for detecting and identifying intestinal parasites. Using both methods, 15,414 outpatient and inpatient specimens were examined. Of 2,773 intestinal parasites recovered, 2,633 (94.9%) were protozoa. The trichrome-stained smear detected 97.0% of the intestinal protozoa and 38.9% of intestinal helminths. We conclude that, in geographic areas where protozoan infections are more common, the trichrome-stained smear alone may be used as a screening method for intestinal parasites if personnel are trained to recognize helminth eggs and larvae in the trichrome-stained smear.