Sir.—I read with interest Taubman and colleagues'1 excellent article in the January 1989 issue of AJDC. A statement made in the article deserves amplification. The authors state, "One reason for lower specificity may be due to possible interference from over-the-counter cold medications. Such medications have been shown to cause false-positive results with this particular latex test" (Culturette Brand Group A STREP ID).2
In the reference cited, I stated that we had indirect evidence that some false-positive results may be due to the patients' ingestion of certain over-the-counter medications. In these cases, the latex test was positive for group A Streptococcus, but in vitro testing showed that β-hemolytic Streptococcus reversibly manifested α-hemolysis when exposed to the medication on blood agar plates. Such plates could possibly be misread as "negative for group A Streptococcus."
In conclusion, the authors are correct in their statement that false-positive results may be reported;
UHLIK DJ. Rapid Streptococcus Testing and Over-the-Counter Cold Medications. Am J Dis Child. 1990;144(2):137. doi:10.1001/archpedi.1990.02150260015001