The diagnosis of streptococcal pharyngitis by the antibody-coated bacteria test

Fluorescein isothiocyanate-labeled goat antihuman immunoglobulin (anti-IgG, anti-IgA, anti-IgM) and anticomplement conjugates were used to detect antibody or complement-coated bacteria from the oropharynx of patients with pharyngitis. Throat smears prepared from patients with a positive culture for group A beta-hemolytic streptococci had significantly more bacteria that stained with labeled antihuman IgG than smears prepared from patients with a negative culture. When compared to the results of a throat culture, the sensitivity, specificity, and predictive value of a positive and negative antihuman IgG stained smear was 91%, 94%, 85%, and 96%, respectively. The results of smears stained with antihuman IgA, IgM or complement did not correlate statistically with the isolation of group A beta-hemolytic streptococci.