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Table 1 Probabilities and cost-estimates used in the cost-analysis for screening of LTBI.

From: Different screening strategies (single or dual) for the diagnosis of suspected latent tuberculosis: a cost effectiveness analysis

Variable

Baseline

Range

Source

Probabilities

   

Prevalence of LTBI

0.30

0.1-0.4

[24, 39, 40]

TST return rate

0.90

0.65-0.95

[14, 27]

T-SPOT.TB sensitivity

0.95

0.83-0.97

[30, 41–43]

T-SPOT.TB specificity

1.00

0.92-0.99

[41, 43]

T-SPOT.TB positive result

0.285

 

Calculated

T-SPOT.TB true positive (PPV)

1.000

 

Calculated

T-SPOT.TB true negative (NPV)

0.979

 

Calculated

T-SPOT.TB true positive (PPV) given a positive TST

1.000

 

Calculated

T-SPOT.TB negative (NPV) given a positive TST

0.987

 

Calculated

QFT-GIT sensitivity

0.89

0.85-0.95

[32, 44]

QFT-GIT specificity

0.95

0.90-0.97

[32, 44]

QFT-GIT positive result

0.302

 

Calculated

QFT-GIT true positive (PPV)

0.884

 

Calculated

QFT-GIT true negative (NPV)

0.953

 

Calculated

QFT-GIT true positive (PPV) given a positive TST

0.930

 

Calculated

QFT-GIT true negative (NPV) given a positive TST

0.971

 

Calculated

TST sensitivity

0.85

0.69-0.95

[30, 41, 42, 45]

TST specificity

0.80

0.65-0.90

[20, 46]

TST positive result

0.395

 

Calculated

TST true positive (PPV)

0.646

 

Calculated

TST true negative (NPV)

0.926

 

Calculated

Start INH treatment

0.80

0.55-0.95

[47]

Develop severe INH hepatitis

0.003

0.003-0.041

[47–50]

Death due to hepatitis

0.00002

0.00001-0.0001

[51, 52]

Efficacy of 3 months INH (LTBI fully cured)

0.21

0.1-0.3

[23, 24, 53]

LTBI not cured (with 3 months INH)

0.79

0.7-0.9

[23, 24, 53]

Efficacy of 6 months INH (LTBI fully cured)

0.65

0.5-0.93

[10, 17, 23, 49, 53, 54]

LTBI not cured (with 6 months INH)

0.35

0.07-0.5

[10, 17, 23, 49, 53]

Post exposure TB

0.025

0.01-0.05

[14, 55]

TB remains latent

0.975

0.95-0.99

[14, 55]

Cost (British Pounds; £s)

   

T-SPOT.TB (kit, consumables and processing) + phlebotomy

55.00

45.00-100.00

Test cost from Royal Free Hospital, London; Phlebotomy cost from [56]

TST(cost of disposables, administration and reading)

16.14

8.07-32.28

[7, 18, 57]

QFT-GIT (kit, consumables and processing) + phlebotomy

45.00

35.00-80.00

Test cost from Royal Blackburn Hospital; Phlebotomy cost from [56]

Treatment for severe INH hepatotoxicity

629.12

314.56-1258.24

[18, 20, 56]

3 months INH treatment

484.38

242.19-968.76

Calculated from [7, 18]

6 months INH treatment

524.59

262.30-1049.18

[7, 18]

Treatment for active TB

7619.67

3809.84-15239.34

[18, 37]

  1. (LTBI-latent tuberculosis infection, TST-Tuberculin Skin Test, INH-isoniazid, PPV-positive predictive value, NPV-negative predictive value).
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BMC Pulmonary Medicine

ISSN: 1471-2466

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