Table 4.
Sensitivity and Specificity of BSI-PCR per pathogen or target in clinical samples
| Pathogen or target | Sensitivity | Specificity | ||||
|---|---|---|---|---|---|---|
| BSI-PCR positive / BC positive |
% (95%-CI) | BSI-PCR positive in 200 negative BC a | % (95%-CI) | |||
| A. Species-specific PCRs | ||||||
| E. faecalis b | 20/27 | 74% | (54–89) | 5 | 98% | (95–100) |
| E. faecium b | 33/50 | 66% | (51–79) | 10 | 95% | (91–98) |
| S. aureus | 28/35 | 80% | (63–92) | 22 | 89% | (84–93) |
| S. pneumoniae | 2/2 | 100% | (16–100) | 5 | 98% | (94–99) |
| A. baumannii | 0/0 | NA | 3 | 99% | (97–100) | |
| E. coli | 17/19 | 89% | (67–99) | 15 | 93% | (88–96) |
| Klebsiella species | 11/17 | 65% | (38–86) | 1 | 100% | (97–100) |
| P. aeruginosa | 27/29 | 93% | (77–99) | 22 | 89% | (84–93) |
| C. albicans | 0/27 | 0% | (0–13) | 0 | 100% | (98–100) |
| C. glabrata | 1/14 | 7% | (0–34) | 0 | 100% | (98–100) |
| C. krusei | 0/0 | NA | 1 | 100% | (97–100) | |
| B. Generic PCRs | ||||||
| Enterococcus genus b | 44/77 | 57% | (45–68) | 4 | 98% | (95–99) |
| Staphylococcus genus b | 41/85 | 48% | (37–59) | 12 | 94% | (90–97) |
| Coagulase negative Staphylococi b, c | 22/50 | 44% | (30–59) | 12 | 94% | (90–97) |
| Gram-positive bacteria d | 51/196 | 26% | (20–33) | 3 | 99% | (96–100) |
| Gram-negative bacteria d | 37/115 | 32% | (24–42) | 5 | 98% | (94–100) |
| 3Candida | 7/31 | 23% | (10–41) | 0 | 100% | (98–100) |
| Pan-Aspergillus | 0/0 | NA | 2 | 99% | (96–100) | |
BC blood culture, CI confidence interval, NA no blood culture isolates available for evaluation
aEach PCR was evaluated in the same set of 200 culture-negative samples
bSelection criteria were applied to reduce the chance of blood culture being discordant positive by contamination
cInferred from positivity in the mecA and/or Staphylococcus genus PCR and negativity in the S. aureus PCR
dFor Gram-positive 8 pathogens were intrinsically not detectable by chosen primers and probes, excluding these resulted into a sensitivity of 27%. For Gram-negative 19 Bacteroides species were intrinsically not detectable, excluding these resulted into a sensitivity of 38%.