Positive Xpert MTB/RIF Ultra Tests and Ct values by incubation time with sample reagent

Spiked CFU/mL

None

(n = 48)

7.5 minutes

(n = 48)

15 minutes (REF)

(n = 48)

n

(%)

(# Trace)

Avg

Ct Value

(Range)

n

(%)

(# Trace)

Avg

Ct Value

(Range)

n

(%)

(# Trace)

Avg

Ct Value

(Range)

10¹

5/12 (42%) (1)

31.45

(30.5 - 32.1)

8/12 (67%) (3)

34.1

(28.1 - 39.6)

8/12 (67%) (1)

29.9

(26.9 - 35.5)

10²

10/12 (83%) (3)

26

(24.5 - 27)

9/12 (75%)

27.5

(23.7 - 35)

10/12 (83%)

25.3

(22.6 - 27.5)

10⁴

12/12 (100%)

22.6

(19.6 - 29.7)

11/12 (92%)

21.8

(16.8 - 27.1)

12/12 (100%)

22.5

(17.6 - 26.9)

10⁶

12/12 (100%)

18.2

(16.3 - 20.2)

12/12 (100%)

17.7

(16.1 - 18.3)

12/12 (100%)

18.4

(17.4 - 19.6)