TABLE 2.
Evaluation of the diagnostic performance of the Sysmex UF-5000 in detecting blood cultures positive for bacterial growth according to different thresholds
| Various criteria for UF-5000 cutoffs and other parametersa | Sensitivities for detection of ≥105 CFU/ml of bacterial culture at various UF-5000 cutoff levels (%) |
|||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 80 | 85 | 88 | 90 | 91 | 93 | 94 | 95 | 96 | 97 | 98 | 99 | |
| UF-5000 bacterial count only | ||||||||||||
| Bacterial count cutoff (no./μl) | 746 | 449 | 255 | 169 | 133 | 122 | 72 | 71 | 50 | 41 | 28 | 15 |
| Specificity (%) | 93.9 | 92.7 | 90.5 | 88.8 | 87.9 | 87.6 | 83.7 | 83.6 | 81.1 | 79.2 | 74.4 | 67.4 |
| PPV for ≥105 CFU/ml (%) | 76.8 | 74.8 | 70.2 | 67.0 | 65.7 | 65.6 | 60.9 | 59.5 | 56.2 | 54.2 | 49.3 | 40.7 |
| Samples below UF-5000 cutoff (%) | 78.8 | 76.8 | 74.6 | 72.8 | 71.9 | 71.3 | 68.0 | 67.7 | 65.5 | 63.8 | 59.8 | 50.9 |
| NPV for no growth (%)* | 49.8 | 50.8 | 51.7 | 52.6 | 52.8 | 53.1 | 54.0 | 54.1 | 54.6 | 55.6 | 57.8 | 61.1 |
| NPV for <104 CFU/ml (%)* | 84.1 | 85.5 | 86.4 | 87.2 | 87.8 | 88.3 | 88.9 | 89.2 | 90.0 | 91.0 | 92.5 | 94.8 |
| NPV for <105 CFU/ml (%)* | 95.0 | 96.3 | 96.8 | 97.2 | 97.5 | 98.0 | 98.2 | 98.5 | 98.7 | 99.0 | 99.4 | 99.5 |
| UF-5000 bacterial count or >15 WBCs/μl | ||||||||||||
| Bacterial count cutoff (no./μl) | 52,895 | 7,678 | 2,989 | 1,659 | 1,176 | 735 | 601 | 422 | 264 | 59 | 45 | 28 |
| Specificity (%) | 74.5 | 72.8 | 72.3 | 71.8 | 71.6 | 71.2 | 70.9 | 70.9 | 70.2 | 66.4 | 65.2 | 62.0 |
| PPV for ≥ 105 CFU/ml (%) | 44.3 | 44.4 | 44.9 | 44.7 | 44.9 | 45.2 | 45.1 | 45.4 | 45.0 | 42.4 | 41.7 | 39.8 |
| Samples below UF-5000 cutoff (%) | 63.5 | 60.9 | 59.9 | 59.3 | 58.9 | 58.1 | 57.7 | 57.5 | 56.8 | 53.5 | 52.4 | 49.6 |
| NPV for no growth (%) | 48.4 | 50.2 | 50.9 | 51.1 | 51.4 | 52.1 | 52.2 | 52.4 | 52.9 | 55.1 | 55.9 | 58.2 |
| NPV for <104 CFU/ml (%)* | 84.0 | 86.0 | 86.8 | 87.1 | 87.6 | 88.5 | 88.8 | 89.2 | 89.6 | 91.0 | 92.1 | 93.6 |
| NPV for <105 CFU/ml (%)* | 93.6 | 95.3 | 96.2 | 96.6 | 97.0 | 97.7 | 98.0 | 98.4 | 98.6 | 99.0 | 99.3 | 99.7 |
| UF-5000 bacterial count or >50 WBCs/μl | ||||||||||||
| Bacterial count cutoff (no./μl) | 4,138 | 1,387 | 880 | 648 | 509 | 400 | 205 | 126 | 59 | 49 | 40 | 15 |
| Specificity (%) | 85.0 | 84.2 | 83.8 | 83.2 | 83.0 | 82.8 | 80.8 | 79.7 | 76.9 | 75.7 | 74.2 | 61.6 |
| PPV for ≥105 CFU/ml (%) | 57.3 | 57.6 | 58.0 | 57.6 | 57.6 | 57.9 | 55.4 | 54.3 | 51.3 | 50.4 | 49.1 | 39.5 |
| Samples below UF-5000 cutoff (%) | 71.9 | 70.3 | 69.3 | 68.4 | 68.1 | 67.5 | 65.6 | 64.6 | 62.1 | 60.9 | 59.6 | 49.3 |
| NPV for no growth (%) | 49.2 | 50.1 | 50.8 | 51.1 | 51.3 | 51.8 | 53.0 | 53.3 | 54.5 | 55.0 | 55.7 | 60.4 |
| NPV for <104 CFU/ml (%)* | 84.1 | 85.4 | 86.5 | 87.0 | 87.3 | 87.9 | 88.7 | 89.2 | 90.2 | 91.2 | 91.8 | 94.8 |
| NPV for <105 CFU/ml (%)* | 94.3 | 95.6 | 96.5 | 97.0 | 97.3 | 97.9 | 98.2 | 98.4 | 98.8 | 99.1 | 99.4 | 99.5 |
a
*, The percentage of specimens with no bacterial growth, <103 CFU/ml bacterial growth, and <104 CFU/ml bacterial growth among samples below the UF-5000 cutoff for each sensitivity level.