Table 3.

Overall relative (within 1 dilution) agreements and 95% CI limits between the visual and spectrophotometric readings and between the NCCLS and XTT methods

Time (h)DrugGrowth levela% Agreement ± 95% CI for the following comparisons:
Visual vs spectrophotometric readingsNCCLS vs XTT methods
NCCLSvis vs NCCLSspbXTTvis vs XTTspbNCCLSvis vs XTTvisbNCCLSsp vs XTTspc
24ITC051.4 ± 5.7d 90.8 ± 3.388.0 ± 3.760.0 ± 11.1e
192.8 ± 3.091.1 ± 3.392.7 ± 3.094.7 ± 5.1
287.7 ± 3.886.0 ± 4.086.8 ± 3.982.7 ± 8.6
367.8 ± 5.4e 75.4 ± 4.9e 79.8 ± 4.6e 73.3 ± 10.0e
468.1 ± 22.6d 67.9 ± 5.368.3 ± 5.473.3 ± 10.0
AMB096.7 ± 2.099.3 ± 0.996.7 ± 2.098.7 ± 2.5
48ITC081.5 ± 4.495.3 ± 2.494.0 ± 2.784.0 ± 8.3
191.6 ± 3.190.9 ± 3.385.1 ± 4.177.3 ± 9.5
287.2 ± 3.883.2 ± 4.282.8 ± 4.373.3 ± 10.0
372.5 ± 5.169.5 ± 5.278.0 ± 4.754.7 ± 11.3
458.1 ± 5.667.5 ± 5.5d 69.6 ± 5.248.0 ± 11.3
AMB098.7 ± 1.3100.0 ± 0.097.0 ± 1.998.7 ± 2.6
  • a See Table 2, footnote b.

  • b A total of 300 comparisons.

  • c A total of 75 comparisons.

  • d The P value (obtained by a two-way ANOVA of log2 MIC end points derived by the two methods) was <0.01.

  • e The P value was <0.05.