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Table 3 CXR performance on all suspects and on suspects excluding those who were ZN-positive. Culture (patient based) used as gold standard (95% confidence interval)

From: The role and performance of chest X-ray for the diagnosis of tuberculosis: A cost-effectiveness analysis in Nairobi, Kenya

CXR on all suspects (n = 998)
Score of the reader Sensitivity Specificity PPV NPV
a) Highly consistent for TB 68 (64–72) 90 (87–93) 0.90 (0.87–0.93) 0.69 (0.65–0.72)
b) Consistent for TB 23 (19–26) 77 (73–80) 0.55 (0.49–0.62) 0.44 (0.40–0.47)
c) Pathology, but no TB 2 (0–3) 96 (94–98) 0.33 (0.16–0.51) 0.43 (0.40–0.46)
"TB" (a+b) 91 (88–93) 67 (62–71) 0.78 (0.74–0.81) 0.84 (0.81–.088)
"any pathology" (a+b+c) 92 (90–94) 63 (58–67) 0.76 (0.73–0.79) 0.86 (0.82–0.90)
CXR on suspects excluding those who were ZN positive (n = 657)
a) Highly consistent for TB 48 (42–55) 90 (87–93) 0.72 (0.65–0.79) 0.77 (0.73–0.81)
b) Consistent for TB 31 (25–37) 77 (73–81) 0.42 (0.34–0.49) 0.68 (0.83–0.90)
c) Pathology but no TB 3 (1–5) 96 (95–98) 0.27 (0.9–0.46) 0.65 (0.62–0.69)
"TB" (a+b) 80 (74–85) 67 (62–71) 0.56 (0.50–0.61) 0.86 (0.83–0.90)
The entire diagnostic process (n = 998)
ZN followed by CXR 93 (91–95) 62 (57–67) 0.76 (0.72–0.79) 0.87 (0.83–0.91)
CXR followed by ZN 89 (86–91) 97(84–90) 0.90 (0.87–0.92) 0.86 (0.83–0.89)