Analysis of variance ( Fig. 3 , part 2), indicated that there was no significant difference (paired t-test, P.0.05) between the inhibition of rRT-PCR of the MS2 external control and the added enterovirus (P.0.05) for protocols A, C, and D. In protocol B the inhibition of the rRT-PCR for enterovirus was actually significantly higher than that for MS2 (P = 0.045). Recovery of enterovirus RNA by the four different protocols was equivalent.