Volume 8, Number 10, October 2002

Bioterrorism-Related Anthrax

Specific, Sensitive, and Quantitative Enzyme-Linked Immunosorbent Assay for Human Immunoglobulin G Antibodies to Anthrax Toxin Protective Antigen

Conrad P. Quinn,* Vera A. Semenova,* Cheryl M. Elie,* Sandra Romero-Steiner,* Carolyn Greene,* Han Li,* Karen Stamey,* Evelene Steward-Clark,* Daniel S. Schmidt,* Elizabeth Mothershed,* Janet Pruckler,* Stephanie Schwartz,* Robert F. Benson,* Leta O. Helsel,* Patricia F. Holder,* Scott E. Johnson,* Molly Kellum,* Trudy Messmer,* W. Lanier Thacker,^* Lilah Besser,* Brian D. Plikaytis,* Thomas H. Taylor, Jr.,* Alison E. Freeman,* Kelly J. Wallace,* Peter Dull,* Jim Sejvar,* Erica Bruce,* Rosa Moreno,* Anne Schuchat,* Jairam R. Lingappa,* Sandra K. Martin,* John Walls,* Melinda Bronsdon,* George M. Carlone,* Mary Bajani-Ari,* David A. Ashford,* David S. Stephens,*† and Bradley A. Perkins*
*Centers for Disease Control and Prevention, Atlanta, Georgia, USA; and †Emory University, Atlanta, Georgia, USA

Figure. Graphic representation of minimum detectable concentration (MDC), reliable detection limit (RDL), and reactivity threshold. The MDC is the concentration of anti-protective antigen antibody (anti-PA) corresponding to the interpolated intersection of the lower asymptote of the upper 95% confidence limit with the 4-parameter logistic log fit of the standard curve data. The RDL is the concentration of anti-PA antibody corresponding to the interpolated intersection of the lower asymptote of the upper 95% confidence limit with the lower 95% confidence limit of the standard’s data. The reactivity threshold was determined as the upper 95% confidence limit of the frequency distribution from log₁₀-transformed optical density (OD) values of control human sera tested at 1/50 dilution. This OD value was converted to an anti-PA immunoglobulin (Ig) G concentration by using the standard curve calibration factor. Where this calculated value is below the MDC of the assay, the MDC was selected as the default reactivity threshold.

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This page last reviewed September 24, 2002

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National Center for Infectious Diseases
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