Table 3.
Comparison of the PCR results from 3 automated nucleic acid extraction systems using a total of 84 nasopharyngeal specimens.
| QIAcube | EZ1 advanced XL | MICROLAB Nimbus IVD | |
|---|---|---|---|
| Positive results | 45 (53.6%) | 45 (53.6%) | 43 (51.2%) |
| True positivea | 42 | 38 | 41 |
| False positivea (virus type) | 3 (PIV4, EV, RSV-B) | 7 (PIV1, ADV (n = 3), RSV-A, RV (n = 2)) | 2 (CoV-NL63, CoV-229E) |
| Negative results | 39 (46.4%) | 39 (46.4%) | 41 (48.8%) |
| True negativea | 36 | 34 | 35 |
| False negativea (virus type) | 3 (FluB, RV, ADV) | 5 (BoV, RV (n = 4)) | 6 (FluB, RV, MPV, BoV, ADV (n = 2)) |
| Sensitivity (%) | 93.3 | 88.4 | 87.2 |
| Specificity (%) | 92.3 | 82.9 | 94.6 |
| Concordance rate (%) | 94.2 | 88.3 | 92.2 |
| Kappa coefficientb (95% CI) | 0.88 (0.79 to 0.97) | 0.76 (0.64 to 0.89) | 0.84 (0.74 to 0.95) |
| RV sensitivity/specificity | 94.7/100.0 | 78.9/96.9 | 94.7/100.0 |
| MPV sensitivity/specificity | 100.0/100.0 | 100.0/100.0 | 85.0/100.0 |
| PIV3 sensitivity/specificity | 100.0/100.0 | 100.0/100.0 | 100.0/100.0 |
| RSV-A sensitivity/specificity | 100.0/100.0 | 100.0/98.7 | 100.0/100.0 |
| ADV sensitivity/specificity | 80.0/100.0 | 100.0/96.2 | 60.0/100.0 |
| Characteristics of three systems | |||
| Principle | Spin column | Magnetic particle | Magnetic particle |
| Sample volume (μL) | ≤200 | 100–400 | 600 |
| Elution volume (μL) | 20–150 | 60–150 | 100 |
| Turnaround timec (min) | 90 | 45 | 150 |
| Sample capacity | 12 | 14 | 48 |
| Automated PCR set-up | Impossible | Impossible | Possible |
aWhen all three automated nucleic acid extraction systems yielded the same results, they were considered “true positive” or “true negative.” If only 1 system yielded negative result, it was considered “false negative.” When the pathogen was detected from only 1 system, multiplex PCR and sequencing analysis were performed to confirm the result. b P < 0.0001 for all values. cincludes lysis step but not the hands-on time.