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Table 4 Performance of pill count adherence in determining viral load suppression

From: Long-term adherence to antiretroviral therapy in a South African adult patient cohort: a retrospective study

Pill count adherence Viral load unsuppressed (≥400 copies/ml) Viral load suppressed (< 400 copies/ml) Sensitivity (95% CI) Specificity (95% CI) PPV (95% CI) NPV (95% CI)
Year 1 on ART (n = 268)
 < 95% 2 (1%) 9 (3%) 97% (94–98) 22% (3–60) 97% (94–99) 18% (2–52)
 ≥ 95% 7 (3%) 250 (93%)
Year 2 on ART (n = 201)
 < 95% 1 (1%) 4 (2%) 98% (95–99) 10% (0–45) 95% (91–98) 20% (1–72)
 ≥ 95% 9 (4%) 187 (93%)
Year 3 on ART (n = 166)
 < 95% 3 (2%) 4 (2%) 97% (94–99) 33% (7–70) 96% (92–99) 43% (10–82)
 ≥ 95% 6 (4%) 153 (92%)
Year 4 on ART (n = 243)
  < 95% 0 4 (2%) 98% (96–100) 0 95% (91–97) 0
  ≥ 95% 13 (5%) 226 (93%)
Year 5 on ART (n = 233)
 < 95% 1 (1%) 11 (5%) 95% (91–98) 9% (0–41) 95% (92–98) 8% (0–38)
 ≥ 95% 10 (4%) 211 (90%)
  1. CI Confidence interval
  2. ART Antiretroviral therapy
  3. PPV Positive predictive value
  4. NPV Negative predictive value
  5. n Number of patients