| Organism | Errors (%) | CIP | CLI | ERY | GEN | OXA | FOX | PEN | RIF | TET | SXT |
| Staphylococcus aureus (n = 66) | Minor | 3 (4.5%) | 4 (6.1%) | 11 (17.0%) | 0 (0%) | 0 (0%) | 0 (0%) | 0 (0%) | 0 (0%) | – | 0 (0%) |
| Major error | 0 (0%) | 0 (0%) | 0 (0%) | 0 (0%) | 1 (1.5%) | 0 (0%) | 0 (0%) | 0 (0%) | – | 0 (0%) | |
| Difference in measured zone sizes (mm) | |||||||||||
| Mean | 1 | 1 | 1 | 1 | 1 | 0 | 2 | 2 | – | 1 | |
| Mode | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 3 | – | 1 | |
| Median (min–max) | 0 (−2 to 6) | 0 (−3 to 5) | 0 (−3 to 6) | 0 (−3 to 4) | 0 (−3 to 5) | 0 (−4 to 3) | 0 (−1 to 7) | 1 (−4 to 7) | – | 0 (−3 to 6) | |
| β-haemolytic streptococci (n = 46) | Minor | – | 7 (15.2%) | 4 (8.7%) | – | – | 0 (0%) | – | 4 (8.7%) | – | |
| Difference in measured zone sizes (mm) | |||||||||||
| Mean | – | 0 | 0 | – | – | – | 0 | – | 0 | – | |
| Mode | – | 0 | 0 | – | – | – | 0 | – | 0 | – | |
| Median (min–max) | – | 0 (−7 to 5) | 1 (−5 to 5) | – | – | – | −2 (−8 to 8) | – | −1 (−4 to 5) | – |
CIP, ciprofloxacin; CLI, clindamycin; ERY, erythromycin; FOX, cefoxitin; GEN, gentamicin; OXA, oxacillin; PEN, penicillin; RIF, rifampicin; TET, tetracycline; SXT, trimethoprim–sulphamethoxazole; –, not tested.