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Table 2 Diagnostic accuracy measures of Xpert MTB/RIF and the biomarkers uIFNγ and ADA using ROC-selected cut-points (definite-TB for sensitivity and non-TB for specificity calculations)

From: Diagnostic accuracy of quantitative PCR (Xpert MTB/RIF) for tuberculous pericarditis compared to adenosine deaminase and unstimulated interferon-γ in a high burden setting: a prospective study

Diagnostic testa

Sensitivity (95% CI) (n/N)c

Specificity (95% CI) (n/N)c

Positive likelihood ratio, LR + (95% CI)

Negative likelihood ratio, LR- (95% CI)

Positive predictive value, PPV (95% CI)

Negative predictive value, NPV (95%CI)

Xpert MTB/RIF

63.8% (52.4 to 75.1)

100% (85.6 to 100)

n/c

0.36

100%

86.6%

44/69* *1 *2

26/26 *4 *5

(0.33 to 0.39)

(98.0 to 100)

(84.0 to 88.7)

uIFNγ (Intergam) (Youden’s, rule-in and rule-out cut-points: ≥44 pg/ml) c

95.7% (88.1 to 98.5)

96.3% (81.7 to 99.3)

25.8

0.045

91.7%

98.1%

67/70* *3 P <0.001

26/27*6

(3.6 to 184)

(0.023 to 0.09)

(88.1 to 94.3)

(96.8 to 98.9)

ADA (rule-in cut-point: >107 IU/ml)

15.7%

96%

    

(9.0 to 26.0)

(80.5 to 99.3)

3.93

0.88

62.7%

72.7%

11/70

24/25

(0.21 to 72.5)

(0.85 to 0.91)

(51.4 to 72.8)

(69.7 to 75.4)

*1 P <0.001

     

ADA (cut-point in current clinical use: ≥35 IU/ml)[5]

95.7%

84%

    

(88.1 to 98.5)

(65.4 to 93.6)

6.0

0.051

71.9%

97.9%

67/70

21/25

(3.7 to 9.8)

(0.026 to 0.10)

(67.3 to 76.1)

(96.4 to 98.7)

*1 *3 P < 0.001

*4 P = 0.03

    

Tygerberg score ≥6

85.3%

77.3%

    

(75.9 to 81)

(56.6 to 89.9)

3.75

0.19

61.7%

92.5%

58/68

17/22

(2.52 to 5.59)

(0.15 to 0.24)

(56.9 to 66.2)

(90.0 to 94.3)

*2 P = 0.004 *3 P = 0.04

*5 P = 0.01 *6 P =0.04

    

Clinical predictors (rule-in cut-point: >6.1)

60.8%

96.3%

    

(49.4 to 71.1)

(81.7 to 99.3)

16.4

0.41

87.6%

85.1%

45/74

26/27

(2.25 to 119.9)

(0.38 to 0.44)

(82.4 to 91.4)

(82.5 to 87.5)

*3 P <0.001

     

Clinical predictors (Youden’s and rule-out cut-point: >3.5) b

91.9%

81.5%

4.96

0.10

68.0%

95.9%

(83.4 to 96.2)

(63.3 to 91.8)

(3.34 to 7.36)

(0.07 to 0.14)

(63.3 to 72.4)

(94 to 97.2)

68/74

22/27

    

*2 P <0.001

*5 P = 0.02

    

Xpert MTB combined with uIFNγ (with uIFNγ if Xpert MTB/RIF negative)

97.1%

100%

n/c

   

(89.9 to 99.2)

(86.7 to 100)

0.03

100%

98.8%

66/68

25/25

(0.01 to 0.08)

(98.7 to 100)

(97.7 to 99.4)

Xpert MTB combined with ADA (with ADA if Xpert MTB/RIF negative)

98.4%

100%

n/c

0.02

100%

99.3%

(91.7 to 99.7)

(85.7 to 100)

(0.002 to 0.11)

(98.7 to 100)

(98.4 to 99.7)

63/64

23/23

  1. aDenominators other than 74 definite- and 27 non-TB patients indicate missing test results. Thus, 5/74 definite- and 1/27 non-TB patients did not have an Xpert MTB/RIF performed; 4/74 definite-TB did not have a uIFNγ (QFT-kit) test performed and 4/74 definite- and 2/27 non-TB did not have an ADA level measurement. Diagnostic accuracy measures presented in this table are for Xpert MTB/RIF performed on 1 ml unconcentrated PF, uIFNγ (both the QFT-kit and Intergam-kits) performed on the supernatants on 3 to 20 ml of centrifuged PF, and ADA performed on 1 to 8 ml of unprocessed PF.
  2. bYouden’s index (the cut-point allowing the most correctly classified) and optimal ‘rule-out’ (the cut-point with the lowest LR-) cut-points for the uIFNγ (both the QFT-kit and Intergam-kits) were the same (QFT: 0.18 IU/l, Intergam: 44 pg/ml) respectively. c P-values compare diagnostic tests for the indicated diagnostic accuracy measure, for example, sensitivity (specific proportions compared indicated by * and corresponding number symbol).
  3. ADA: adenosine deaminase; CI: confidence interval; n/c: not calculable as denominator equals zero; PF, pericardial fluid; uIFNγ: unstimulated interferon gamma. The reference standard was culture and/or histopathology pathognomonic of TB†. TB prevalence = 30% used for predictive value estimates.
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BMC Medicine

ISSN: 1741-7015

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