Table 4:
Optimal CT Value Cutoffs for Predicting Smear Positivity among Culture-Positive Participants
| Optimal CT Value Cutoff (95% CI) | Correctly Classified % (95% CI) | Sensitivity % (95% CI) | Specificity % (95% CI) | PPV % (95% CI) | NPV % (95% CI) | Median (IQR) TTCP if CT ≥ Cutoff (d) | Median (IQR) TTCP if CT < Cutoff (d) | |
|---|---|---|---|---|---|---|---|---|
| Maximizing correct classification |
||||||||
| Overall (n = 275) | 27.5 (24.9–32.3) | 81.8 (76.7–86.1) | 88.9 (83.4–93.0) | 69.1 (58.8–78.1) | 84.0 (78.0–89.0) | 77.0 (67.0–85.4) | 18 (12–24) | 10 (7–14) |
| HIV infected (n = 157) | 26.7 (23.5–32.6) | 78.3 (71.1–84.5) | 77.5 (66.8–86.1) | 79.2 (68.5–87.6) | 79.5 (68.8–87.8) | 77.2 (66.4–85.9) | 18 (13–23) | 12 (9–15) |
| HIV uninfected (n = 108) | 28.8 (24.9–35.8) | 89.8 (82.5–94.8) | 96.6 (90.6–99.3) | 55.6 (30.8–78.5) | 91.6 (84.0–96.3) | 76.9 (46.2–95.0) | 14 (8–22) | 9 (6–12) |
| “Rule out” (sensitivity of at least 95%) |
||||||||
| Overall (n = 275) | 30.5 (27.2–34.7) | 78.9 (73.6–83.6) | 95.5 (91.3–98.0) | 48.4 (38.2–58.8) | 77.3 (71.1–82.6) | 85.4 (73.3–93.5) | 19 (13–25) | 11 (7–15) |
| HIV infected (n = 157) | 31.6 (27.9–36.1) | 66.9 (58.9–74.1) | 95.0 (87.7–98.6) | 38.7 (27.6–50.6) | 62.2 (53.0–70.9) | 87.9 (71.8–96.6) | 19 (14–26) | 11 (7–15) |
| HIV uninfected (n = 108) | 28.8 (24.9–35.8) | 89.8 (82.5–94.8) | 96.6 (90.6–99.3) | 55.6 (30.8–78.5) | 91.6 (84.0–96.3) | 76.9 (46.2–95.0) | 14 (8–22) | 9 (6–12) |
Definition of abbreviations: CI = confidence interval; CT = cycle threshold; IQR = interquartile range; NPV = negative predictive value; PCR = polymerase chain reaction; PPV = positive predictive value; TTCP = time to culture positivity in days.