TABLE 3.
Performance summary of the BCID panel versus the comparator assays for bacteria in both clinical and seeded positive blood cultures combined
| Organism | Isolates detecteda: BCID/comparator |
No. of results: BCID/comparator |
Sensitivity or PPAb: TP/(TP + FN) (%) | 95% CI | Specificity or NPAb: TN/(TN + FP) (%) | 95% CI | ||||
|---|---|---|---|---|---|---|---|---|---|---|
| Clinical arm | Seeded arm | TP +/+ | FP +/− | FN −/+ | TN −/− | |||||
| Gram-positive bacteria | ||||||||||
| Enterococcus | 102/101 | 29/29 | 127 | 4 | 3 | 2,073 | 127/130 (97.7) | 93.4–99.5 | 2,073/2,077 (99.8) | 99.5–99.9 |
| L. monocytogenes | 0/0 | 36/36 | 36 | 0 | 0 | 2,171 | 36/36 (100) | 90.3–100 | 2,171/2,171 (100) | 99.8–100 |
| Staphylococcus | 780/797 | 2/1 | 770 | 12 | 28 | 1,397 | 770/798 (96.5) | 95.0–97.7 | 1,397/1,409 (99.1) | 98.5–99.6 |
| S. aureus | 257/257 | 0/0 | 253 | 4 | 4 | 1,946 | 253/257 (98.4) | 96.1–99.6 | 1,946/1,950 (99.8) | 99.5–99.9 |
| Streptococcus | 140/141 | 63/62 | 198 | 5 | 5 | 1,999 | 198/203 (97.5) | 94.3–99.2 | 1,999/2,004 (99.8) | 99.4–99.9 |
| S. agalactiae (group B) | 18/18 | 18/18 | 36 | 0 | 0 | 2,171 | 36/36 (100) | 90.3–100 | 2,171/2,171 (100) | 99.8–100 |
| S. pneumoniae | 26/25 | 12/12 | 36 | 2 | 1 | 2,168 | 36/37 (97.3) | 85.8–99.9 | 2,168/2,170 (99.9) | 99.7–100 |
| S. pyogenes (group A) | 8/7 | 31/31 | 38 | 1 | 0 | 2,168 | 38/38 (100) | 90.7–100 | 2,168/2,169 (99.9) | 99.7–100 |
| Total | 1,331/1,346 | 191/189 | 1,494 | 28 | 41 | 16,093 | 1,494/1,535 (97.3) | 96.4–98.1 | 16,093/16,121 (99.8) | 99.7–99.9 |
| Gram-negative bacteria | ||||||||||
| A. baumannii | 16/14 | 40/37 | 51 | 5 | 0 | 2,151 | 51/51 (100) | 93.0–100 | 2,151/2,156 (99.8) | 99.5–99.9 |
| Enterobacteriaceae | 307/310 | 187/188 | 490 | 4 | 8 | 1,705 | 490/498 (98.4) | 96.9–99.3 | 1,705/1,709 (99.8) | 99.4–99.9 |
| E. cloacae complex | 24/22 | 17/17 | 38 | 3 | 1 | 2,165 | 38/39 (97.4) | 86.5–99.9 | 2,165/2,168 (99.9) | 99.6–100 |
| E. coli | 149/148 | 6/5 | 150 | 5 | 3 | 2,049 | 150/153 (98.0) | 94.4–99.6 | 2,049/2,054 (99.8) | 99.4–99.9 |
| K. oxytoca | 6/6 | 54/58 | 59 | 1 | 5 | 2,142 | 59/64 (92.2)c | 82.7–97.4 | 2,142/2,143 (99.9) | 99.7–100 |
| K. pneumoniae | 74/71 | 37/34 | 102 | 9 | 3 | 2,093 | 102/105 (97.1) | 91.9–99.4 | 2,093/2,102 (99.6) | 99.2–99.8 |
| Proteus | 22/22 | 17/17 | 39 | 0 | 0 | 2,168 | 39/39 (100) | 91.0–100 | 2,168/2,168 (100) | 99.8–100 |
| S. marcescens | 22/22 | 55/55 | 76 | 1 | 1 | 2,129 | 76/77 (98.7) | 93.0–100 | 2,129/2,130 (99.9) | 99.7–100 |
| H. influenzae | 8/8 | 35/35 | 43 | 0 | 0 | 2,164 | 43/43 (100) | 91.8–100 | 2,164/2,164 (100) | 99.8–100 |
| N. meningitidis | 1/1 | 35/35 | 36 | 0 | 0 | 2,171 | 36/36 (100) | 90.3–100 | 2,171/2,171 (100) | 99.8–100 |
| P. aeruginosa | 52/52 | 0/0 | 51 | 1 | 1 | 2,154 | 51/52 (98.1) | 89.7–100 | 2,154/2,155 (99.9) | 99.7–100 |
| Total | 681/676 | 483/481 | 1135 | 29 | 22 | 23,091 | 1,135/1,157 (98.1) | 97.1–98.8 | 23,091/23,120 (99.9) | 99.8–99.9 |
Culture or culture and 16S rRNA gene sequencing for A. baumannii.
The data in these columns are based on the combined results from the clinical and seeded specimens. Sensitivity refers to performance with clinical specimens, while PPA refers to performance with seeded specimens. Despite the differences in names and usage, they were calculated identically. Likewise, specificity refers to performance with prospective samples, while NPA is used for seeded specimens. They were also calculated identically. These data were obtained in the initial analyses and have not been changed to reflect subsequent investigations of discordant results. Investigations of discordant results are described in Results and summarized in Table 5.
K. oxytoca is the only organism that apparently failed to meet the prespecified criterion of a sensitivity of >95%. However, this was due to an unavoidable error in phenotypic identification. When this was resolved, the sensitivity for this organism exceeded 98.3%.