Positive Xpert MTB/RIF Ultra Tests and Ct values by SR Incubation Time

(SR 3:1)

Spiked CFU/mL

None (n = 16)

7.5 minutes

(n = 16)

15 minutes (REF) (n = 16)

n

(%)

(# Trace)

Avg

Ct Value

(Range)

n

(%)

(# Trace)

Avg

Ct Value

(Range)

n

(%)

(# Trace)

Avg

Ct Value

(Range)

10¹

0/4

n/a

1/4

(25%)

39.6

4/4

(100%) (1)

27.2

(26.9 - 27.4)

10²

3/4

(75%) (1)

26.8

(26.6 - 27)

3/4

(75%)

26.8

(26.6 - 27)

4/4

(100%)

25.3

(22.6 - 27.5)

10⁴

4/4

(100%)

24.2

(19.6 - 29.7)

4/4

(100%)

24.2

(19.6 - 29.7)

4/4

(100%)

21.2

(17.6 - 24.3)

10⁶

4/4

(100%)

18.3

(17.1 - 20.2)

4/4

(100%)

18.3

(17.1 - 20.2)

4/4

(100%)

18.7

(17.9 - 19.1)