Rapid latex agglutination compared with the throat culture for the detection of group A streptococcal infection.

Abstract

The Culturette Brand rapid latex agglutination test was compared with the throat culture for accuracy in detecting Group A beta-hemolytic streptococci (GABHS) on paired throat swabs from 1047 children with suspected streptococcal pharyngitis. In this comparison the rapid latex agglutination test had a sensitivity of 78%, a specificity of 88%, a positive predictive value of 52% and a negative predictive value of 96%. In 45 study patients from whom it was possible to obtain paired acute and convalescent sera, the latex agglutination test and the throat culture were compared against each other for detection of infection due to GABHS as evidenced by a 4-fold or greater titer rise of serum antistreptococcal antibodies. The latex agglutination test detected and failed to detect the same number of infections as the throat culture. Thus although a significant number of false positive latex agglutination tests occurred when compared to the throat culture, there is limited evidence in this study that the latex agglutination test is equal to the throat culture in detecting patients who have serologically confirmed infection due to GABHS.