Table 2.
Sensitivity and Specificity of Binary Drug Concentration Thresholds to Predict Future Viral Load ≥20 Copies/mL
| All Paired Specimens (n = 365), % | VL <20 Copies/mL at Preceding Visit (n = 255), % | DBS Done <90 Days Before VL (n = 85), % | ||||
|---|---|---|---|---|---|---|
| TFV-DP in DBS Concentration at Preceding Visit | Sensitivity | Specificity | Sensitivity | Specificity | Sensitivity | Specificity |
| ≤LLOQ | 35.1 (27.5–43.3) | 98.1 (95.3– 99.5) | 0 (0–0.1) | 99.5 (97.1–99.9) | 36.1 (28.0–44.9) | 98.1 (94.6–99.6) |
| ≤350 fmol/punch | 54.3 (46.0–62.4) | 96.3 (92.8–98.4) | 12.3 (5.5–22.8) | 98.4 (95.5–99.7) | 56.4 (47.5–65.0) | 95.6 (91.2–98.2) |
| ≤700 fmol/punch | 62.9 (54.7–70.6) | 89.7 (84.9–93.4) | 29.2 (18.6–41.8) | 91.6 (86.7–95.1) | 66.2 (57.5–74.1) | 87.5 (81.4–92.2) |
| ≤1250 fmol/punch | 80.8 (73.6–86.7) | 51.4 (51.4–44.5–58.3) | 61.5 (48.6–73.4) | 52.1 (44.8 – 59.4) | 82.0 (74.4–88.1) | 52.5 (44.4–60.4) |
| ≤1850 fmol/punch | 95.4 (90.7–98.1) | 15.9 (11.3–21.5) | 89.2 (79.1–95.6) | 14.7 (14.7–10.0–20.6) | 96.2 (91.4–98.8) | 16.9 (11.4–23.6) |
Abbreviations: DBS, dried blood spot; LLOQ, lower limit of quantification; TDF-DP, tenofovir diphosphate; VL, viral load.