TABLE 2.
Estimated disease prevalence and sensitivity and specificity of using serotype-specific qPCR to diagnose VTPPa
| Serotype-specific pneumococcal DNA load cutoff value (no. of copies/ml) | UAD assay |
UAD assay + sputum cultureb |
||||||
|---|---|---|---|---|---|---|---|---|
| Disease prevalence (%)c | Sensitivity (%) | Specificity (%) | Youden index | Disease prevalence (%) | Sensitivity (%) | Specificity (%) | Youden index | |
| ≥103 | 11.1 (7.4–15.7) | 81.5 (61.9–93.7) | 93.5 (89.4–96.4) | 0.75 | 12.3 (8.4–17.1) | 83.3 (65.3–94.4) | 94.9 (91.0–97.4) | 0.782 |
| ≥104 | 81.5 (61.9–93.7) | 94.5 (90.5–97.1) | 0.76 | 83.3 (65.3–94.4) | 95.9 (92.2–98.1) | 0.792 | ||
| ≥105 | 74.1 (53.7–88.9) | 95.4 (91.7–97.8) | 0.695 | 76.7 (57.7–90.1) | 96.7 (93.4–98.7) | 0.734 | ||
| ≥106 | 70.4 (49.8–86.2) | 97.7 (94.7–99.2) | 0.681 | 70.0 (50.6–85.3) | 98.6 (96.0–99.7) | 0.686 | ||
| ≥107 | 63.0 (42.4–80.6) | 98.2 (95.3–99.5) | 0.612 | 63.3 (43.9–80.1) | 99.1 (96.6–99.9) | 0.624 | ||
| ≥108 | 51.9 (31.9–71.3) | 99.1 (96.7–99.9) | 0.51 | 46.7 (28.3–65.7) | 99.1 (96.6–99.9) | 0.458 | ||
| ≥109 | 22.2 (8.6–42.3) | 99.1 (96.7–99.9) | 0.213 | 20.0 (7.7–38.6) | 99.1 (96.7–99.9) | 0.191 | ||
a
qPCR, quantitative PCR; UAD, serotype-specific urinary antigen detection assay. Values in parentheses are 95% confidence intervals.
b
Determined by conventional sputum culture and by use of the Quellung reaction's bacterial load cutoff value of 1.0 × 105 CFU/ml.
c
Estimated from the reference standard or the composite reference standard result assuming 100% specificity.