Evaluation of the broth microdilution plate methodology for susceptibility testing of Mycobacterium tuberculosis in Peru

Table 3 Performance of BMD UKMYC6 plate methodology compared to APM for drug resistance determination

Drug	BMD	APM		Sensitivity (95% CI)	Specificity (95% CI)	PPV (95% CI)	NPV (95% CI)	Categorical agreement	Cohen's kappa
Drug	BMD	R	S	Sensitivity (95% CI)	Specificity (95% CI)	PPV (95% CI)	NPV (95% CI)	Categorical agreement	Cohen's kappa
Rifampicin	R	383	2	0.93 (0.90, 0.95)	0.97 (0.90, 1.00)	0.99 (0.98, 1.00)	0.71 (0.60, 0.79)	0.94	0.78
	S	28	67
Isoniazid	R	381	3	0.98 (0.97, 0.99)	0.91 (0.75, 0.98)	0.99 (0.98, 1.00)	0.83 (0.66, 0.93)	0.98	0.85
	S	6	29
Ethambutol	R	107	8	0.72 (0.64, 0.79)	0.96 (0.93, 0.98)	0.93 (0.87, 0.97)	0.84 (0.79, 0.88)	0.87	0.71
	S	41	211
Ethionamide	R	89	18	0.66 (0.57, 0.74)	0.94 (0.91, 0.97)	0.83 (0.75, 0.90)	0.87 (0.83, 0.90)	0.86	0.64
	S	46	307
Kanamycin	R	36	0	0.68 (0.54, 0.80)	1.00 (0.99, 1.00)	1.00 (0.90, 1.00)	0.96 (0.94, 0.98)	0.97	0.79
	S	17	437
Levofloxacin	R	47	3	0.87 (0.75, 0.95)	0.99 (0.98, 1.00)	0.94 (0.83, 0.99)	0.98 (0.97, 0.99)	0.98	0.89
	S	7	424

Results with borderline MICs were excluded from the analysis
APM: 7H10 Agar Proportion Method, BMD: Broth Microdilution, R: Number of phenotypically resistant strains, S: Number of phenotypically susceptible strains. PPV: Positive Predictive Value, NPV: Negative Predictive Value. 95% CI: 95% Confidence Interval

ISSN: 1471-2334