Comparative laboratory evaluation of three antigen detection methods for diagnosis of Haemophilus influenzae type b disease

Cerebrospinal fluid, urine, serum, and other body fluid specimens from pediatric patients with systemic disease were tested with Bactigen latex agglutination (555 specimens), Phadebact coagglutination (319 specimens), and counterimmunoelectrophoresis (335 specimens) for the presence of Haemophilus influenzae type b antigen. All three methods showed good sensitivity for detecting antigen in the cerebrospinal fluid of patients with culture-positive meningitis (greater than or equal to 86% sensitivity). However, coagglutination and counterimmunoelectrophoresis were much less sensitive (less than or equal to 40%) than latex agglutination (96%) for detecting antigen in other body fluid specimens in culture-positive, nonmeningeal H. influenzae disease. Bactigen latex agglutination was also more sensitive than the other procedures for detecting antigen in specimens from patients with culture-negative, presumed H. influenzae disease. Comparative testing of fluids spiked with known quantities of purified H. influenzae b polyribosephosphate capsular polysaccharide revealed an apparent 100-fold greater sensitivity with Bactigen as compared with the other two methods. Although all three methods showed good specificity (greater than 98%), both agglutination methods gave a few false-positive results. In a clinical setting where both meningeal and nonmeningeal H. influenzae b disease are encountered frequently, Bactigen latex agglutination appears to be superior to coagglutination and counterimmunoelectrophoresis for detecting antigen in body fluids.