Table 2.

Performance of Genotype MTBDRplus at different ramp rates for the detection of M. tuberculosis-complex DNA (TUB-band), stratified by smear status, when done directly on sputa from Xpert MTB/RIF-positive patients. Genolysed extract from each specimen was tested at each ramp rate. TUB-band detection and the rate of indeterminates worsened in smear-negative specimens with use of the incorrect ramp rate.

Smear microscopy status	Ramp rate (°C/s)	TUB-band positive (%)	Determinate (%)	Indeterminate (%)
Positive n = 52	4.0	52/52 (100)	52/52 (100)	0/52 (0)
	2.2*	52/52 (100)	52/52 (100)	0/52 (0)
Negative n = 55	4.0	32/55 (58)	27/32 (84)	5/32 (16)
	2.2*	42/55 (76) (p = 0.042)	41/42 (98) (p = 0.164)	1/42 (2) (p = 0.039)

P-values are for comparisons between ramp rates for smear-negative specimens.

^*Manufacturer-recommended ramp rate.