TABLE 2.
MIC and categorical interpretation agreement among participating laboratories for each antibiotic
| Antibiotic | Total no. of isolates | Total no. of pairwise comparisons | Modal MIC range (mg/liter) | % participant MICs that differ from the modal MICs by the following no. of 2-fold dilutions |
% agreement (no. of comparisons with concordant results/total no. of comparisons) by: |
Modal MICs at categorical interpretation breakpoints |
||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| ≤−2 | −1 | Same | 1 | ≥2 | Modal MIC (±1 log2) | Categorical interpretation | % | No. | ||||
| Penicillin | 106 | 838 | 0.016–64 | 4.1 | 15.9 | 66.0 | 11.9 | 2.2 | 93.79 (786/838) | 93.32 (1,006/1,078) | 38.67 | 41/106 |
| Tetracycline | 107 | 880 | 0.125–64 | 3.8 | 19.1 | 56.6 | 16.5 | 4.4 | 91.82 (808/880) | 84.23 (871/1,034) | 67.29 | 72/107 |
| Erythromycin | 103 | 434 | 0.063–32 | 3.5 | 13.4 | 68.7 | 12.7 | 1.8 | 94.70 (411/434) | 90.89 (549/604) | 50.49 | 52/103 |
| Spectinomycin | 112 | 571 | 8–32 | 1.2 | 11.0 | 70.4 | 16.1 | 1.2 | 97.55 (557/571) | 98.67 (744/754) | 0.00 | 0/112 |
| Ceftriaxone | 117 | 978 | 0.0005–0.25 | 3.6 | 17.7 | 63.2 | 14.1 | 1.4 | 94.99 (929/978) | 96.07 (1,027/1,069) | 23.93 | 28/117 |
| Ciprofloxacin | 102 | 817 | 0.002–16 | 2.9 | 15.7 | 63.7 | 14.9 | 2.8 | 94.25 (770/817) | 94.48 (1,129/1,195) | 23.53 | 24/102 |
| Cefixime | 102 | 528 | 0.002–0.5 | 1.3 | 15.2 | 71.8 | 10.2 | 15.2 | 97.16 (513/528) | 98.10 (927/945) | 11.76 | 12/102 |
| Azithromycin | 105 | 779 | 0.032–16 | 1.5 | 16.3 | 68.8 | 13.0 | 0.4 | 98.07 (764/779) | 96.16 (877/912) | 22.85 | 24/105 |