Skip to main content

Table 2 Agreement between three serological tests used for the detection of H5 antibodies in ducks experimentally infected with H5N1

From: Comparison of serological assays for detecting antibodies in ducks exposed to H5 subtype avian influenza virus

Test comparison 8 dpi 15 dpi 22 dpi 29 dpi 34 dpi Overall Kappa
HI-CRBC and HI-HRBC:       
Kappa for dichotomised results (95%-CI)1 0.44 (0.01-0.88) 1 (1.00-1.00) 0.74 (0.27-1.00) 1 (1.00-1.00) 1 (1.00-1.00) 0.86 (0.73-0.99)
Weighted kappa for log titres (95%-CI)2 0.56 (0.30-0.83) 0.85 (0.65-1.00) 0.61 (0.32-0.77) 0.85 (0.70-1.00) 0.66 (0.49-0.84) 0.8 (0.71-0.85)
HI-CRBC and VN:       
Kappa for dichotomised results (95%-CI)1 0.55 (0.04-1.00) 1 (1.00-1.00) 0.38 (−0.33-1.00) 0.74 (0.27-1.00) 0.41 (−0.18-1.00) 0.76 (0.60-0.93)
Weighted kappa for log titres (95%-CI)2 0.49 (0.27-0.71) 0.76 (0.46-0.95) 0.50 (0.25-0.66) 0.36 (0.02-0.52) 0.41 (0.24-0.65) 0.68 (0.58-0.74)
HI-HRBC and VN:       
Kappa for dichotomised results (95%-CI)1 0.19 (−0.10-0.49) 1 (1.00-1.00) 0.74 (0.27-1.00) 0.74 (0.27-1.00) 0.41 (−0.18-1.00) 0.69 (0.50-0.88)
Weighted kappa for log titres (95%-CI)2 0.19 (0.01-0.46) 0.71 (0.41-0.93) 0.41 (0.12-0.61) 0.37 (0.17-0.58) 0.36 (0.12-0.63) 0.55 (0.42-0.63)
  1. Ten ducks were sampled before inoculation with H5N1 virus and at 8, 15, 22, 29 and 34 days post inoculation (dpi). The kappa statistic (95% confidence interval1) was used to compare dichotomised test results (positive versus negative) and a weighted kappa statistic (95% confidence interval2) was used to compare log titers at each sampling period and across all sampling periods.
  2. 1The analytical method was used to calculate confidence intervals for dichotomised test results [35].
  3. 2The bootstrap method with 100 bootstrap replications was used to calculate confidence intervals for the log titers [36, 37].
  4. Abbreviations: HI-CRBC (Haemagglutination inhibition test using chicken red blood cells), HI-HRBC (Haemagglutination inhibition test using horse red blood cells), VN (Virus neutralisation test), CI (confidence interval).