TABLE 2.
Relationship between the predicted number of PCR replicates needed to achieve various test sensitivities and C. pneumoniae concentrations
| Probita | C. pneumoniae concn (IFU/ml)b | No. of replicates needed to achieve sensitivity ofc:
|
|||
|---|---|---|---|---|---|
| 50% | 80% | 90% | 95% | ||
| 0.01 | 0.01 | 69 | 161 | 230 | 299 |
| 0.05 | 0.03 | 14 | 32 | 45 | 59 |
| 0.10 | 0.05 | 7 | 16 | 22 | 29 |
| 0.20 | 0.09 | 4 | 8 | 11 | 14 |
| 0.30 | 0.15 | 2 | 5 | 7 | 9 |
| 0.40 | 0.24 | 2 | 4 | 5 | 6 |
| 0.50 | 0.35 | 1 | 3 | 4 | 5 |
| 0.60 | 0.53 | 1 | 2 | 3 | 4 |
| 0.70 | 0.81 | 1 | 2 | 2 | 3 |
| 0.80 | 1.34 | 1 | 1 | 2 | 2 |
| 0.90 | 2.70 | 1 | 1 | 1 | 2 |
| 0.95 | 4.79 | 1 | 1 | 1 | 1 |
| 0.99 | 14.10 | 1 | 1 | 1 | 1 |
a
Probit, predicted proportion of replicates positive from probit regression analysis (SPSS), based on 10 replicates of 16 dilutions of C. pneumoniae ATCC VR-1310 (see the text).
b
C. pneumoniae ATCC VR-1310 concentration as calculated from probit analysis.
c
Replicates calculated in Microsoft Excel spreadsheet from the following equation: probability (at least 1 positive in n replicates) = 1 − (1 − probit)n.