Abstract
The distribution of Neisseria meningitidis serogroup B and C polysaccharide antigen in blood and the prognostic significance of antigen concentration was examined by ultrasound-enhanced immunoagglutination of coated microparticles. Specimens (169 sera/plasma from 145 patients with confirmed meningococcal disease) were tested retrospectively. The ultrasonic immunoassay detected serum antigen in 136 samples from 112 patients. Titration of antigen-positive specimens allowed estimation of blood antigen concentration. The modal blood antigen titre was 1/16, corresponding to an estimated polysaccharide concentration of 0.85 μg/ml. The lowest mean blood antigen concentration found ultrasonically was 0.05 μg/ml; compared to the 1.98 μg/ml found by conventional latex agglutination, this represents an approximately 30-fold improvement in sensitivity. Three grades of outcome were correlated with the presenting antigen titre in 83 patients: (i) <2 weeks hospitalisation, (ii) ≥2 weeks hospitalisation and (iii) mortality. High polysaccharide concentrations correlated with mortality. Nine of 15 patients with a serum antigen titre of 1/64 or greater (≥3.4 μg/ml polysaccharide) died, whereas no patient with titres equal to or less than 1/4 (≤0.21 μg/ml) died, including those patients in whom antigen was undetectable by ultrasonic immunoassay. Increasing antigen concentration significantly correlated with severity of outcome (P<0.001). Ultrasound-enhanced agglutination provides a rapid prognostic indicator by sensitive measurement of serum antigen level.
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Sobanski, M., Barnes, R., Gray, S. et al. Measurement of Serum Antigen Concentration by Ultrasound-Enhanced Immunoassay and Correlation with Clinical Outcome in Meningococcal Disease. EJCMID 19, 260–266 (2000). https://doi.org/10.1007/s100960050473
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DOI: https://doi.org/10.1007/s100960050473