NASBA

Short for nucleic acid based amplification, this RNA amplification system allows direct amplification of RNA samples using three different enzymes in a cyclic manner, viz. reverse transcriptase, RNAse H and T7 RNA polymerase. Total RNA is purified from the samples and a cocktail of three enzymes is added along with dNTPs and NTPs, an isothermal incubation of 90 mins causes a million fold amplification of the target RNA. There is no need of any thermal cycler in this system and also minimizes the chances of carry over contamination, when handling a number of samples. The products are detected with Molecular Beacons.

Further reading:
NASBA: a novel, isothermal detection technology for qualitative and quantitative HIV-1 RNA measurements. Romano JW, van Gemen B, Kievits T. Clin Lab Med. 1996 Mar; 16(1):89-103.