Table 1.

MTBDRsl Performance on a Dilution Series of Drug-Susceptible-TB and XDR-TB Strains (10⁴, 10³, and 10² CFU/mL) at Ramp Rates of 2.2°C/second (Manufacturer-Recommended) or 4.0°C/second (3 Replicates in Triplicate for Each Ramp Rate; 18 Total MTBDRsl Results)

Ramp rate (°C/second)	TUB-band–positive	TUB-band–positive
		Indeterminate for any gene locus	Incorrect banding call	Incorrect drug class diagnostic call	Valid result
2.2	16/18∗ (89)	2/16† (13)	22/400‡ (6)	2/32§ (6)	14/16† (88)
4.0	17/18∗ (94), P = 0.547	3/17† (18), P = 0.680	33/425¶ (8), P = 0.193	2/34‖ (6), P = 0.950	14/17† (82), P = 0.680

Data are expressed as n/N (%). Accuracy for M. tuberculosis–complex-DNA (TUB-band) and then further analysis of indeterminate rates, incorrect banding calls, and incorrect drug class diagnostic calls were done. No significant differences were seen between ramp rates using dilution series. P values are for within-column comparisons between different ramp rates. CFU, colony-forming units; Incorrect banding call, the presence or absence of a band deviating from the true banding call; Incorrect drug class diagnostic call, the presence or absence of banding patterns resulting in deviation of the true susceptibility to a drug class; Indeterminate, one or more gene locus control is absent; MTBDRsl, GenoType MTBDRsl VER 2.0; TB, tuberculosis; TUB-band–positive, positive for Mycobacterium tuberculosis–complex-DNA; Valid result, TUB-band–positive, determinate for all gene locus controls, thus having diagnostic calls for both drug classes; XDR, extensively drug resistant.

^∗Two strains × 3 replicates × 3 dilutions.

^†TUB-positive strips.

^‡Sixteen TUB-band–positive strips × 25 bands per strip.

^§Sixteen TUB-band–positive strips × 2 drug class diagnostic calls.

^¶Seventeen TUB-band–positive strips × 25 bands per strip.

^‖Seventeen TUB-band–positive strips × 2 drug class diagnostic calls.