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Pneumococcal and Haemophilus influenzae type b antigen detection in children at risk for occult bacteremia
Insights
Latex agglutination accurately detects Haemophilus influenzae type b (Hib) in febrile children. However, it shows low sensitivity for pneumococcal bacteremia, indicating a need for improved diagnostic methods for Streptococcus pneumoniae.
Area of Science:
- Pediatric Infectious Diseases
- Clinical Microbiology
- Diagnostic Immunology
Background:
- Occult bacteremia in young febrile children poses a diagnostic challenge.
- Accurate and rapid detection of common bacterial pathogens like Streptococcus pneumoniae and Haemophilus influenzae type b (Hib) is crucial for timely treatment.
- Current diagnostic methods require evaluation for sensitivity and specificity in at-risk pediatric populations.
Purpose of the Study:
- To prospectively evaluate the utility of antigen detection assays for pneumococcal and Hib bacteremia in young febrile children.
- To compare the sensitivity and specificity of latex agglutination and enzyme immunoassay for detecting these pathogens.
- To assess the potential of latex agglutination for rapid diagnosis of occult Hib bacteremia.
Main Methods:
- Prospective evaluation of 576 febrile children (3-30 months) at risk for occult bacteremia.
- Exclusion of patients with severe infections (septic shock, meningitis, epiglottitis).
- Testing of serum and urine samples using latex agglutination and enzyme immunoassay for pneumococcal and Hib antigens.
Main Results:
- All five cases of Hib bacteremia were detected by latex agglutination (urine and serum).
- Latex agglutination detected only one of 16 cases of pneumococcal bacteremia.
- Enzyme immunoassay showed improved sensitivity over latex agglutination for pneumococcal antigen but still missed several cases; both assays demonstrated >95% specificity.
Conclusions:
- Latex agglutination is a sensitive and specific tool for diagnosing occult Hib bacteremia in young febrile children.
- Current latex agglutination and enzyme immunoassay methods lack sufficient sensitivity for detecting occult pneumococcal bacteremia.
- Further development of sensitive diagnostic assays for Streptococcus pneumoniae is warranted.
Abstract:
We prospectively evaluated pneumococcal and Haemophilus influenzae type b antigen detection in serum and urine of young (3 to 30 months of age) febrile (temperature greater than or equal to 39 degrees C) children at risk for occult bacteremia. Patients with septic shock, meningitis, or epiglottitis were excluded. Of 576 patients, 16 had pneumococcal bacteremia (final diagnoses: primary bacteremia, nine; otitis media, four; pneumonia, two; unknown, one), and five had H influenzae b bacteremia (final diagnoses: primary bacteremia, two; cellulitis, two; arthritis, one). Latex agglutination was positive in all five patients with H influenzae b bacteremia (positive in three of three urine specimens, three of four sera tested) but only one of 16 patients with pneumococcal bacteremia (positive in one of seven urine samples, zero of 13 sera tested). Both assays had specificities of greater than 95%. Nonspecific agglutination occurred in 7% of specimens tested. Enzyme immunoassay for pneumococcal antigen, although more sensitive than latex agglutination, failed to detect antigen in ten sera and three urine specimens from patients with pneumococcal bacteremia. Thus, neither latex agglutination nor enzyme immunoassay was sufficiently sensitive for detection of occult pneumococcal bacteremia. Latex agglutination for H influenzae b holds promise as a sensitive and specific test for rapid diagnosis of occult bacteremia due to H influenzae b.