Sensitivity limits of multiplex RT-PCR. Lane 1 Amplification from tenfold diluted cDNA; lanes 2–6 amplicons from 10 −2 to 10 −6 fold diluted cDNA. Lanes 1–6 amplicons obtained with multiplexing kit; lanes 7–12 amplification with hot-start Taq DNA polymerase at same dilutions; lane M 100 bp marker