Table 2.

Interlaboratory variability in GCV IC50determinations by initial (phase 1) and ACTG consensus (phase 2) plaque reduction assays using plaque-purified viruses

LaboratoryGCV IC50 (μM) for:
AD169aXbaFaC9208bC9209b
Phase 1Phase 2Phase 1Phase 2Phase 1Phase 2Phase 1Phase 2
A5.623.17
B5.491.8686.91>960.661.2279.3969.09
C9.043.6725.43>961.639.81NA>96
D1.3310.9948.66NAc
E2.340.2914.149.3022.111.98>9664.24
F1.023.185.4216.030.400.1467.68>96
G3.873.87
H1.201.7417.8619.1696.4028.25
I2.701.4037.2028.695.924.37>100>96
J2.209.5728.4843.943.607.72>966.79
K9.586.0729.0426.11NA
Total no. of assays1111986667
Mean IC50 4.044.1630.5641.905.724.2189.2565.19
CVd 75.581.681.283.314591.614.454.7
No. (%) resistant0 (0)0 (0)8 (84)8 (100)1 (17)0 (0)6 (100)6 (86)
  • a Cell-free laboratory strains.

  • b Cell-associated clinical isolates.

  • c NA, IC50 could not be determined due to inconsistent results.

  • d CV determined as (standard deviation/mean) × 100%.