Anal. 15 min after the sample is applied. RICT with several pairs of MoAbs showed a high sensitivity for the detection of recombinant N\Ag as well as viral N\Ag of SARS\CoV. rSN122 and rSN21\2 were the best MoAbs for immobilized antibody and enzyme labeling, respectively. With regard to analytical sensitivity, RICT detected N\Ag at 31 pg/mL for recombinant N\Ag, and at 1.99102 TCID50/mL for SARS\CoV. The specificity of RICT was 100% when 150 human sera and 50 nasopharyngeal aspirates (NSPs) were used. RICT based on an EIA using the rSN122/rSN21\2 pair is a sensitive, specific, and reliable rapid assay for detecting N\Ag in SARS\CoV treated with either heat or Triton X\100. J. Clin. Lab. 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