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 | |
|---|---|---|---|---|---|---|---|---|---|
| R | S | ||||||||
| 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