Volume 21, Number 1—January 2015
Dispatch
Use of Treponema pallidum PCR in Testing of Ulcers for Diagnosis of Primary Syphilis1
Table 1
Summary of the various indices of performance of Tp-PCR compared with DFM, serologic testing, or an enhanced definition for diagnosis of primary syphilis*
Reference testing | Sensitivity (95% CI) | Specificity (95% CI) | Likelihood ratio (95% CI) |
κ coefficient (95% CI) | Post-test probability (95% CI) |
||
---|---|---|---|---|---|---|---|
Positive | Negative | If Tp-PCR is positive (PPV) | If Tp-PCR is negative (1 − NPV) | ||||
DFM, n = 170 | 93.8% (79.2%–99.2%) | 90.6% (84.4%–94.9%) | 9.95 (5.89–16.82) | 0.07 (0.02–0.26) | 0.74 (0.62–0.87) | 69.8% (53.9%–82.8%) | 1.6% (0.2%–5.6%) |
Serologic, n = 239 | 78.5% (68.4%–86.5%) | 93.4% (88.2%–96.8%) | 11.84 (6.44–21.77) | 0.23 (0.16–0.35) | 0.73 (0.64–0.82) | 87.3% (78.0%–93.8%) | 11.9% (7.3%–17.9%) |
Enhanced definition, n = 170 | 87.5% (74.8%–95.3%) | 99.2% (95.5%–100.0%) | 106.75 (15.11–753.95) | 0.13 (0.06–0.27) | 0.90 (0.82–0.97) | 97.7% (87.7%–99.9%) | 4.7% (1.8%–10.0%) |
*Tp-PCR, Treponema pallidum PCR; DFM, darkfield microscopy; PPV, positive predictive value; NVP, negative predictive value.
1Preliminary results from this study were presented at the 53rd Interscience Conference on Antimicrobial Agents and Chemotherapy, September 10–13, 2013, Denver, Colorado, USA.