Pharyngeal gram stains in the treatment of sore throats.

The use of the direct pharyngeal Gram stain for diagnosis of group A beta-hemolytic streptococcal pharyngitis was evaluated. Seventy-five consecutive out-patients presented with pharyngitis (or high fever in infants) were studied with pharyngeal cultures and Gram stains. Gram stains were read as either positive, negative, or indeterminate for streptococcal pharyngitis. When these predictions were correlated with the resulting culture growth of group A beta-hemolytic streptococci, the predictive value of a throat smear Gram stain was found to be significant (p less than 0.005). There were two false positives and three false negatives. Approximately one third of the smears were in the indeterminate category. Although the Gram stain of a pharyngeal smear was found to be less sensitive than the routine throat culture, the ability to obtain inexpensive rapid microbiological information suggests that the Gram stain can be used as a quick screening procedure.