To the Editor.—Fluorescent antibody (FA) tests for enteropathogenic Escherichia coli (EEC) are presumptive diagnostic screening tests which have proved to be sensitive and relatively specific when used as recommended.1-3 If the procedure is modified without adequate evaluation of the effect on test results, however, equivocal results may be obtained. Several instances of misuse of the test which have come to our attention have prompted this note of caution.
The FA test for EEC was devised for examination of fecal smears from infants with diarrhea and for monitoring infants at risk of E coli infection. False positive results will occur if the reagents are used on fecal smears from older children (beyond 2 years) and adults. Enrichment of the fecal specimens from infants with EEC diarrhea usually is not necessary. If only rare organisms are seen in smears from fecal swabs, incubation of the fecal saline suspensions for several