Table 3.

Comparison of Banding and Drug Class Diagnostic Calls Done on a Dilution Series of DS-TB and XDR-TB Strains and Clinical Specimens Interpreted by Three Experienced Readers

Ramp rate (°C/second)	DS-TB strain		XDR-TB strain		Clinical specimens
	Different banding call between readers	Different drug class diagnostic call between readers	Different banding call between readers	Different drug class diagnostic call between readers	Different banding call between readers	Different drug class diagnostic call between readers
2.2	0/225∗ (0)	0/18† (0)	1/225∗ (0.4)	0/18† (0)	34/1300‡ (3)	5/104§ (5)
4.0	1/225∗ (0.4), P = 0.317	1/18† (6), P = 0.311	3/225∗ (1), P = 0.313	0/18† (0), P > 0.999	52/1300‡ (4), P = 0.030	8/104§ (8), P = 0.390

Data are expressed as n/N (%). Differences in banding calls or drug class diagnostic calls did not differ between the three readers at either ramp rate for the dilution series of cells, neither did the drug class diagnostic calls in the clinical specimens; however, significant difference between readers for banding calls on the clinical sputa occurred. P values are for within-column comparisons between different ramp rates. Significant P values are marked in bold. banding call, the presence or absence of a band deviating from the true banding call; diagnostic call, the presence or absence of banding patterns resulting in deviation of the true susceptibility to a drug class; DS-TB, drug-susceptible tuberculosis; XDR-TB, extensively drug-resistant tuberculosis.

^∗One strain × 3 replicates × 3 dilutions × 25 bands per strip.

^†One strain × 3 replicates × 3 dilutions × 2 drug class diagnostic calls.

^‡Fifty-two clinical specimens × 25 bands per strip.

^§Fifty-two clinical specimens × 2 drug class diagnostic calls.