Table 2. Calculation of the 95% and 99% detection limit of the rtLC DBS assay using probit analysis.

Actual concentration (copies/reaction)	Measured concentration (median copies/reaction)	Number of positive reactions/total test reactions (%)
Four concentrations > = 4688	--	100/100(100%)
292	248	99% *
937	941	25/25 (100%)
187	188	44/46 (95.7%)
136	112	95% *
83	56	17/22 (77.3%)
37	39	38/47 (80.9%)
17	9	11/22 (50%)
7	0	2/22 (9%)

^*The assay sensitivity was calculated using 22 replicate measurements for low range concentrations between 7 and 187 copies. Results from concentration 37, 187 and 937 copies from 25 runs of standard curve data were also used for Probit fitting. The data used for the analyses are shown in regular typeface and the estimated 99% and 95% detection limits are shown in boldface.