Table 2.
Diagnostic yield of vortexing and sonication fluid culture, depending on two cutoff values (≥1 CFU/ml and ≥50 CFU/ml fluid)a
| Cutoff value | No. (%) of PJI (n = 35) | No. (%) of AF (n = 100) | % sensitivity (95% CI) | % specificity (95% CI) | % PPV (95% CI) | % NPV (95% CI) | % PLR (95% CI) | % NLR (95% CI) |
|---|---|---|---|---|---|---|---|---|
| Cutoff ≥ 1 CFU/ml | ||||||||
| Sonication fluid | 25 (71)c | 7 (7)d | 71 (54–85) | 93 (86–97) | 78 (60–91) | 90 (83–95) | 10 (5–21) | 0 (0–1) |
| Vortexing fluid | 24 (69) | 8 (8)b | 69 (51–83) | 92 (85–96) | 75 (57–89) | 89 (82–95) | 9 (4–17) | 0 (0–1) |
| Cutoff ≥50 CFU/ml | ||||||||
| Sonication fluid | 21 (60) | 1 (1)e | 60 (42–76) | 99 (95–100) | 95 (77–99) | 88 (80–93) | 60 (8–430) | 0 (0–1) |
| Vortexing fluid | 14 (40) | 1 (1)e | 40 (24–58) | 99 (95–100) | 93 (68–99) | 83 (75–89) | 40 (5–293) | 1 (0–1) |
PJI, prosthetic joint infection; AF, aseptic failure; 95% CI, 95% confidence interval; PPV, positive predictive value; NPV, negative predictive value; PLR, positive likelihood ratio; NLR, negative likelihood ratio.
Propionibacterium acnes (n = 5), coagulase-negative staphylococci (n = 2), Corynebacterium spp. (n = 1).
In 4 of 25 (16%) cases, sonication cultures grew <50 CFU/ml. In all 4 cases, patients had previously received antimicrobial treatment (3 cases were caused by coagulase-negative staphylococci and 1 by Pasteurella multocida).
P. acnes (n = 5), coagulase-negative staphylococci (n = 2).
Corynebacterium spp. (n = 1).