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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)