Positive Xpert MTB/RIF Ultra Tests and Ct values by CSF volume

Spiked CFU/mL

0.5 mL (n = 48)

1 mL (n = 96)

n (%)

(# Trace)

Median Ct

Average Ct (range)

n (%)

(# Trace)

Median Ct

Average Ct (range)

10¹

5/12

(42%) (1)

23.1

29.7

(22.3 - 39.6)

16/24

(67%) (4)

30.8

31.1

(24.3 - 32.1)

10²

10/12

(83%) (1)

26.4

25.6

(23.3 - 27.6)

19/24

(79%) (2)

26.4

29.1

(24.3 - 33.4)

10⁴

12/12

(100%)

21.9

23.1

(17.6 - 29.7)

23/24

(96%)

18.2

21.9

(16.8 - 26.9)

10⁶

12/12

(100%)

18.3

18.3

(17.1 - 20.2)

24/24

(100%)

18.2

18

(16.1 - 18.6)