TABLE 1.
Pneumococcal PCR testing protocol: interpretation of test results
| Result type | PCR resulta
|
Further action | Result interpretationb | ||
|---|---|---|---|---|---|
| Pneumolysin (ply) | Autolysin (lytA) | Internal process control | |||
| Initial results | +/+ | +/+ | NA | None | Positive |
| +/− | +/+ | NA | None | Positive | |
| +/+ | +/− | NA | None | Positive | |
| +/− | +/− | NA | None | Positive | |
| −/− | −/− | + | None | Negative | |
| +/+ | −/− | + | Repeat lytA PCR | See below | |
| −/− | +/+ | NA | Repeat ply PCR | See below | |
| +/− | −/− | + | Repeat lytA and ply PCRs | See below | |
| −/− | +/− | + | Repeat lytA and ply PCRs | See below | |
| −/− | −/− | − | Inhibitory; repeat DNA extraction and both PCRs | See below | |
| Combined results after | ≥1 + | ≥1 + | NA | Positive | |
| repeated PCR tests | ≥2 + | −/− −/− | + | Positive | |
| −/− −/− | ≥2 + | NA | Positive | ||
| 1 + | −/− −/− | + | Negative | ||
| −/−/ −/− | 1 + | NA | Negative | ||
| Repeat extractionc | −/− | −/− | − | Sample inhibitory | |
a
NA, not applicable; +, positive PCR assay result; −, negative PCR assay result.
b
“See below,” refer to the rows for combined results after repeated PCR tests or repeat extraction.
c
Any other combination treated as for initial results.