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Comparison of a multiplexed fluorescent covalent microsphere immunoassay and an enzyme-linked immunosorbent assay for measurement of human immunoglobulin G antibodies to anthrax toxins.

Biagini RE; Sammons DL; Smith JP; MacKenzie BA; Striley CAF; Semenova V; Steward-Clark E; Stamey K; Freeman AE; Quinn CP; Snawder JE
Clin Diagn Lab Immunol 2004 Jan; 11(1):50-55
Recently, the Centers for Disease Control and Prevention reported an accurate, sensitive, specific, reproducible, and quantitative enzyme-linked immunosorbent assay (ELISA) for immunoglobulin G (IgG) antibodies to Bacillus anthracis protective antigen (PA) in human serum (C. P. Quinn, V. A. Semenova, C. M. Elie et al., Emerg. Infect. Dis. 8:1103-1110, 2002). The ELISA had a minimum detectable concentration (MDC) of 0.06 microgram/ml, which, when dilution adjusted, yielded a whole-serum MDC of 3.0 microg of anti-PA IgG per ml. The reliable detection limit (RDL) was 0.09 microgram/ml, while the dynamic range was 0.06 to 1.7 microgram/ml. The diagnostic sensitivity of the assay was 97.6% and the diagnostic specificity was 94.2% for clinically verified cases of anthrax. A competitive inhibition anti-PA IgG ELISA was also developed to enhance the diagnostic specificity to 100%. We report a newly developed fluorescence covalent microbead immunosorbent assay (FCMIA) for B. anthracis PA which was Luminex xMap technology. The FCMIA MDC was 0.006 microgram of anti-PA IgG per ml, the RDL was 0.016 microgram/ml, and the whole-serum equivalent MDC was 1.5 micrograms/ml. The dynamic range was 0.006 to 6.8 microgram/ml. Using this system, we analyzed 20 serum samples for anti-PA IgG and compared our results to those measured by ELISA in a double-masked analysis. The two methods had a high positive correlation (r2 = 0.852; P < 0.001). The FCMIA appears to have benefits over the ELISA for the measurement of anti-PA IgG, including greater sensitivity and speed, enhanced dynamic range and reagent stability, the use of smaller sample volumes, and the ability to be multiplexed (measurement of more than one analyte simultaneously), as evidenced by the multiplexed measurement in the present report of anti-PA and anti-lethal factor IgG in serum from a confirmed clinical anthrax infection.
Diagnostic-techniques; Antibody-response; Antigens; Bioassays; Biological-monitoring; Immunoglobulins; Enzyme-activity; Infectious-diseases; Bacterial-infections; Microorganisms; Toxins; Sampling
National Institute for Occupational Safety and Health, Division of Applied Research and Technology, Biomonitoring and Health Assessment Branch, Biological Monitoring Laboratory Section, MS C-26, 4676 Columbia Parkway, Cincinnati, OH 45226
Publication Date
Document Type
Journal Article
Email Address
Funding Type
Interagency Agreement
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NIOSH Division
Priority Area
Research Tools and Approaches: Exposure Assessment Methods
Source Name
Clinical and Diagnostic Laboratory Immunology
Page last reviewed: September 2, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division