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

Fluorescein isothiocyanate-labelled 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 labelled 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 percent, 94 percent, 85 percent, and 96 percent, 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.