A New Era in TB Control: Can We Replace the TST

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A New Era in TB Control Can We Replace the TST?

• Charles L. Daley, M.D.
• National Jewish Medical and Research Center
• Denver, Colorado

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Reported TB Cases United States, 19822005
No. of Cases
Year
All case counts and rates for 19932003 have been
revised based on updates received by CDC as of
April 1, 2005.
3
Number of TB Cases inU.S.-born vs. Foreign-born
Persons United States, 19932005
No. of Cases
All case counts and rates for 19932003 have been
revised based on updates received by CDC as of
April 1, 2005.
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A New Era in TB Control Can We Replace the TST?

• A Brief Look at the TST
• Interferon-gamma Release Assays (IGRAs)
• Utility of IGRAs in Diagnosing TB
• Can IGRAs be Used to Monitor Therapy?
• Can We Replace the TST?

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Kochs Lymph
...treated with Kochs tuberculininstead of
curing her, it rotted her arm right off. Yes, I
remember. Poor Jane! However, she makes a good
living out of that arm now by showing it at
medical lectures (Act 1) The Doctors
Dilemma G. B. Shaw, 1902
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Tuberculin Skin TestImportant Historical Points

• 1890 - Robert Koch
• 1939 - Florence Seibert
• 1969 - Gryzybowski and Holden
• 1972 - Division of Biologic Standards
• 1976 - FDA appointed a Panel on Skin Test
  Antigens
• Tubersol (Connaught)
• Aplisol (Parke Davis)

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Tuberculin Skin TestingMantoux Method
5 TU of PPD
48 to 72 hours
Interpretation depends on persons risk factors
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Tuberculin Skin TestingMantoux Method

• in vivo test
• inter-reader variability
• 2 patient visits
• results in 2 to 3 days
• cross reaction with BCG NTM

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In Vivo and In Vitro Diagnostic Tests
IFN-?
Presentation of mycobacterial antigens
IL-8, etc.
TNF-?
IFN-?
Antigen presenting cell
Memory T-cell
IL-8, etc.
TNF-?
Andersen P, et al. Lancet 20003561099
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ESAT-6 / CFP-10 Complex
Pym et al, 2003
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Species Specificity of ESAT-6 and CFP-10
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Whole Blood IFN-? AssayQuantiFERON-TB Test
Cellestis
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T-Spot.TB?
Nil Control
Infection
Infection
Positive Control
Oxford Immunotec
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Whole Blood IFN-? Assay Response to PPD

• Site Australia
• 60 medical students
• QIFN pre and post BCG
• 19 patients with TB
• Antigen-human PPD

Johnson PDR, et al. Clin Diag Labor Immunol.1999
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Whole Blood IFN-? Assay Response to ESAT-6

• Site Australia
• 60 medical students
• QIFN pre and post BCG
• 19 patients with TB
• Antigen ESAT-6

Johnson PDR, et al. Clin Diag Labor Immunol.1999
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ELISPOT with ESAT-6
50 healthy contacts with well-defined
degrees of exposure ESAT-6 correlated
with degree of exposure ESAT-6 was
not correlated with BCG status
Lalvani A, et al. Lancet 20013572017.
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M. Tuberculosis Infection in Health Care Workers
in India

• Cross-sectional comparison of 726 HCWs aged 18 to
  61 years (median -22)
• TST vs. QFT-G (in-tube)
• Site - Mahatma Gandhi Institute of Medical
  Sciences in Sevagram, India
• 493 (68) had direct contact with TB patients
• 514 (71) had BCG vaccine scars

Pai M, et al. JAMA. 20052932746
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M. Tuberculosis Infection in Health Care Workers
in India

• 360 (50) were positive by either TST or IFN-?
  assay
• 266 (31) were positive by both tests
• Agreement between the tests was high with kappa
  of 0.61.
• Increasing age and years in health profession
  associated with positive tests.
• BCG had little impact on either test results

Pai M, et al. JAMA. 20052932746
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Correlation Between TST and IFN-? Assay Responses
Pai M, et al. JAMA. 20052932746
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QFT-G (in tube) in HIV-infected Persons
607 HIV patients tested
17 excluded due to technical or logistic problems
590 patients with valid QFT test
20 QFT indeterminate (13 1 TB risk factors)
543 QFT (184 1 TB risk factors)
27 QFT (21 1 TB risk factors)
Brock I, et al. Resp Res 2006756
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QFT-G (in tube) in HIV-infected Persons
Risk Factors QFT QFT OR (95 CI)
p-value Prev. TB 22 (4) 5 (19) 4.9
(1.7-14.1) p8 (30) 4.9 (2.0-11.8) parea 98 (17) 15 (56) 5.7 (2.6-12.5)
p1 risk factor 184 (34) 21 (78)
7.2 (2.9-18.2) pBrock I, et al. Resp Res 2006756
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ELISPOT Based Assay in Children?
293 children with suspected TB
31 ELISPOT assays not available
262 with ELISPOT results
13 without TB (9 with TST results)

• With
• possible TB or
• lost (93 with TST
• results)

76 with highly probably TB (73 with TST results)
57 with confirmed TB (43 with TST results)
Liebeshuetz S, et al. Lancet 20043642196
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ELISPOT Based Assay in Children?

• Sensitivity
• ELISPOT TST p-value
• Age
• 36 mos 81 73
• p-value 0.53 0.01
• HIV
• Negative/UK 85 70
• Positive 73 36 0.005
• p-value 0.12 0.002
• Z score
• 2 86 76
• 2 78 44 0.002
• p-value 0.24 0.0003

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Diagnosis of TB
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Interferon Gamma Release Assays

• 24 year old asymptomatic man receiving
  azathioprine for Crohns disease
• He was married to a women with MDR-TB
• TST - 4 mm (negative)
• ELISPOT - positive
• BAL was AFB positive and grew Mtb with same
  5-drug resistance pattern as wife

Index case
Contact
Richeldi, L. et. al. Ann Intern Med
2004140709-713
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Whole Blood Test Using ESAT-6 and CFP-10 for
Diagnosis of TB
Prospective evaluation of QFT in the diagnosis of
TB
Ravn P, et al. Clin Diag Lab Immun 200512491.
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Interferon Gamma Release Assays
Positive responses with Patients (n)
QFT Smear Culture All PTB (35)
83 46 63 97 EPTB (13)
92 31 42 92 All TB (48)
85 42 59 96
Ravn P, et al. Clin Diag Lab Immun. 200512491
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Concentration of ESAT-6 Specific, IFN-? Cells in
Pleural Fluid

• 10 patients with pleural TB
• ELISPOT using ESAT-6
• ESAT-6 specific, IFN-? T-cells were concentrated
  15-fold in pleural fluid vs blood
• Such cells were absent in 8 controls with
  nonTB-related effusions

Wilkinson KA, et al. CID 200540184
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Monitoring Response to Treatment
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Change in ELISPOT After 3 months of Treatment For
TB

• Site - Italy
• 18 patients with TB
• ELISPOT at baseline and
• after 3 months of therapy
• All patient had a positive response at baseline
• Response to ESAT-6 peptides was only detectable
  in the five patients who were still
  microbiologically positive and/or who had no
  clinical improvement

Carrara et al. CID 200438754
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Change in ELISPOT after Treatment of TB Patients

• Site - Gambia
• Study Design - Prospective cohort
• ELISPOT performed on 89 patients with sputum
  smear and culture positive TB at baseline and
  after 12 months
• Conclusion - Successful treatment is accompanied
  by significant reduction in M. tuberculosis
  specific ELISPOT count

Aiken AM, et al. BMC Infect Dis. 2006666
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Proportion of Cured Sputum Positive TB Cases at
Recruitment and 12 Months Later
Aiken AM, et al. BMC Infect Dis. 2006666
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Change in ELISPOT with Treatment of Children with
TB

• Site - Cape Town, South Africa
• Design - Prospective evaluation of ELISPOT in
  children with clinical dx of TB
• Subset retested after 1, 3, and 6 months of
  therapy
• 49 of 70 children with clinical TB had response
  to ESAT-6 or CFP-10

Nicol MP, et al. CID 2005401301
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Change in ELISPOT with Treatment of Children with
TB
Nicol MP, et al. CID 2005401301
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Change in ELISPOT with Treatment of LTBI

• Site - Cape Town, South Africa
• Design - Prospective evaluation of ELISPOT in 33
  people with LTBI
• Treatment with INH resulted in 1.8 fold increase
  in spot forming cells within 26 4 days followed
  by decrease
• No change in 8 patients who were not treated

Wilkinson KA, et al. JID 2006193354
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Effect of Treatment of LTBI on T Cell Response
Wilkinson KA, et al. JID 2006193354
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T-SPOT.TB vs. QFT-G!
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Comparison of T-Spot.TB and QFT-TB Gold

• Site - Italy
• Design - Prospective study of 393 consecutively
  enrolled patients with LTBI or suspected TB
• Agreement with the TST and the two IGRAs was
  similar
• Indeterminate results were more common with
  QFT-TB Gold than T-Spot.TB.
• Indeterminate results were more likely in young
  children (treatment

Ferrara G, et al. Lancet. 20063671328-1334
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Comparison of Test Results Among Contacts
TST QFT-G T-SPOT.TB All contacts 62
(54) 25 (22) 39 (34) 29 (35) contacts 0.0001 0.0923
Ferrara G, et al. Lancet. 20063671328-1334
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T-SPOT.TB Test and QFT-TB Gold
Ferrara G, et al. Lancet. 20063671328-1334
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Comparison of T-Spot.TB and QFT-TB Gold
Test results Active TB () Low risk for TB No.
of subjects 87 131 TST ( 10 mm) 58
(66.7) 28 (21.4) QFT-G positive 61 (70.1) 11
(8.4) T-SPOT.TB positive 83 (95.4) 20 (15.3)
Lee JY, et al. ERJ. 2006
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IGRAs Performance
Performance TST RD-1 Based Characteristics
IFN-gamma assays Est. sensitivity 75-90
85-95 Est. specificity 80-90
95-100 Correlates with exposure Yes
Yes Progression to TB Yes Insufficient
data Results change with Rx No Yes
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Interferon Gamma Release Assaysvs. Tuberculin
Skin Test
IGRA
TST

• In vitro
• Multiple antigens
• No boosting
• Not affected by BCG
• One patient visit
• Minimal inter-reader variability
• Results in one day

• In vivo
• Single antigens
• Boosting
• May be affected
• Two patient visits
• Significant inter-reader variability
• Results in 2-3 days

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Can We Replace the TST?