TABLE 2

Molecular assay performance compared with reference testing for the diagnosis of TBa

Performance measurementPercentage (95% CI) for tests performed on:
Pellets (SOC)Sputa (direct)Pellets
Sputum 3Sputum 1 (SOC)Sputum 2Sputum 4Sputum 3
Smear microscopyMGIT cultureXpert MTB/RIF, visit 1Abbott RealTime MTB assay, visit 1Abbott RealTime MTB assay, visit 2Xpert MTB/RIF, visit 2Abbott RealTime MTB assay, visit 2
Comparison with MGIT culture (n = 193)
    Sensitivity43.5 (31.7–56.7) 79.0 (66.8–88.3)83.9 (72.3–92.0)88.7 (78.1–95.3)91.9 (82.2–97.3)85.5 (74.2–93.1)
    Specificity98.5 (94.6–99.8) 96.9 (92.4–99.2)92.3 (86.3–96.2)94.6 (89.2–97.8)97.7 (93.5–99.5)92.4 (86.4–96.3)
    PPV93.1 (77.2–99.2) 92.5 (81.8–97.9)83.9 (72.3–92.0)88.7 (78.1–95.3)95.0 (86.1–99.0)84.1 (7278–92.1)
    NPV78.7 (71.6–84.7) 90.7 (84.6–95.0)92.3 (86.3–96.2)94.6 (89.2–97.8)96.2 (91.4–98.8)93.1 (87.3–96.8)
Comparison with MGIT culture (HIV-positive cohort only) (n = 142)$
    Sensitivity37.5 (22.7–54.2) 70.0 (53.5–83.4)75.0 (58.8–87.3)82.5 (67.2–92.7)87.5 (73.2–95.8)77.5 (61.5–89.2)
    Specificity98.0 (93.1–99.8) 96.1 (90.3–98.9)93.1 (86.2–97.2)95.1 (88.9–98.4)97.1 (91.6–99.4)93.1 (86.4–97.2)
    PPV88.2 (63.6–98.5) 87.5 (71.0–96.5)81.1 (64.8–92.0)86.8 (71.9–95.6)92.1 (78.6–98.3)81.6 (65.7–92.3)
    NPV80.0 (71.9–86.6) 89.1 (81.7–94.2)90.4 (83.0–95.3)93.3 (86.6–97.3)95.2 (89.1–98.4)91.3 (84.2–96.0)
Comparison with MGIT culture (HIV-negative cohort only) (n = 44)$
    Sensitivity55.0 (31.5–76.9) 95 (75.1–99.9)100 (83.2–100)100 (83.2–100)100 (83.2–100)100 (83.2–100)
    Specificity100 (86.3–100) 100 (86.3–100)92.0 (74.0–99.0)91.7 (73.0–99.0)100 (86.3–100)88.0 (68.8–97.5)
    PPV100 (71.5–100) 100 (82.4–100)90.9 (70.8–98.9)90.9 (70.8–98.9)100 (83.2–100)87.0 (66.4–97.2)
    NPV73.5 (55.6–87.1) 96.2 (80.4–99.9)100 (85.2–100)100 (84.6–100)100 (86.3–100)100 (84.6–100)
Comparison with clinical case definition# (Any TB including definite, possible, probable TB) (n = 202)
    Sensitivity31.6 (22.4–41.9)74.7 (63.9–83.6)62.8 (52.2–72.5)61.7* (51.1–71.5)64.9 (54.4–74.5)67 (56.6–76.4)66 (55.5–75.4)
    Specificity100 (96.6–100)100 (96.5–100)100 (96.6–100)95.3* (89.4–98.5)95.3 (89.4–98.5)100 (96.6–100)94.4 (88.3–97.9)
    PPV100 (88.4–100)100 (94.2–100)100 (93.9–100)92.1* (82.4–97.4)92.4 (83.2–97.5)100 (94.3–100)91.2 (81.8–96.7)
    NPV62.4 (54.8–69.7)83.1 (75.2–89.2)75.5 (67.6–82.3)73.9* (65.8–81.0)75.6 (67.4–82.5)77.7 (69.9–84.3)76.1 (68.0–83.1)
  • a *, test not done (n = 1); $, of the 193 MGIT results, there were 7 patients with an unknown HIV status, and these were excluded from the HIV stratification; #, reported to minimize differences between specimen collection and testing due to limited volume and SOC, return visits, and potential use of antibiotics.