Table 1.

Detection limit of GPC RT-PCR with array hybridization for different Lassa virus strains, determined by replicate testing and probit analysis^a

Lassa virus strain	Origin of strain	Genetic lineage	95% detection limit
			No. of RNA copies/ml sample	No. of RNA copies/reaction mixture
Lib05-1580/121	Liberia	IV	2,216	25.9
CSF	Nigeria	III	1,036	12.1
GA391	Nigeria	III	479	5.6
803213	Nigeria	II	347	4.0
LP	Nigeria	I	4,295	50.1

^aVirus RNA was in vitro transcribed from plasmid by using the MegaScript T7 kit (Ambion, Austin, TX), purified with the RNeasy minikit (Qiagen, Hilden, Germany), and quantified spectrophotometrically. Different RNA concentrations were tested with replicates, and the corresponding fraction of positive reactions was determined. The 95% detection limit of the assay was calculated from these data by probit analysis using PriProbit version 1.63 (6).