INTERFERON GAMA RELEASE ASSAYS (IGRA)

Dr Zayre ErturanI.U. Istanbul Medical Faculty

Dep. of Medical Microbiology

I have no conflicts of interests to disclose

Anderson P, et al. Lancet 2000; 356:1099

Measurement of INF production

Measurement of induration

TST versus in-vitro assays

Advantages/disadvantages of IGRAs over TST

TST IGRA

Setting of test in vivo in vitrointernal controls no yesCross-reactivity with BCG yes noCross-reactivity with NTM yes noInterpretation of test subjective objectiveBoosting effect yes noNumber of visits two oneTime required for result 48-72 h 16-24 h

Test cost low highLaboratory requirement not exist exist Drawing blood no yes except M. marinum, M. szulgai, M. kansasii, Richeldi L. Am J Respir Crit Care Med 2006; 174:736

M. flavescens Nahid P. Proc Am Thorac Soc 2006;3: 10 ECDC guidance

QuantiFERON –TB Gold In-TUBE (QFT-GIT) (Cellestis Ltd Australia)

T-SPOT. TB ( Oxford Immunotec, UK)

www.cellestis.com

Interpretation Criteria for QuantiFERON-TB Gold In Tube Test

www.cellestis.com

Positive

Negative

Indeterminate

T-SPOT. TB – Application

www.oxfordimmunotec.com

positive positive

negative Indeterminate

borderline

Indeterminate

T SPOT.TB-Interpretation

www.oxfordimmunotec.com

Nil control

Panel A:ESAT 6

Panel B:CFP 10

Positive control

Either (Panel A-Nil) or (Panel B-Nil) ≥ 8 spots

Either (Panel A-Nil) or (Panel B-Nil) ≥ 8 spots

Both (Panel A-Nil) and ( Panel B-Nil) ≤ 4 spots

Both (Panel A-Nil) and ( Panel B-Nil) ≤ 4 spots

Differences in TSPOT. TB and QFT-GIT

T-SPOT. TB QFT-GIT Antigens ESAT-6, CFP-10 ESAT-6, CFP-10, TB 7.7

Readout units INF- spot-forming cells International units of INF-

Technological platform ELISpot ELISA

Test’s substrate PBMC Whole blood Outcome measure Number of INF -producing T cells Serum concentration of INF- Readout system Enumeration of spots by naked eye, Measurement of optical density magnifying lens, or automated counter using automated reader

Lab. Procedures counting , separating and Incubation of blood collection dispersing of PBMCs tubes, no additional procedure

Interpretation of IGRA results

• Positive M. tuberculosis infection likely latent / active ?

• Negative M. tuberculosis infection unlikely, but cannot be excluded

• Indeterminate ? low mitogen, high nil values - Incorrect sample collecting, handling, incubation or delay of processing - other «technical» factors - poor patient immun function test should be repeated

• Borderline test should be repeated

IGRA Guidelines • 25 countries, 2 supranational organizations 33 guidelines/position papers USA (CDC, AAP), Canada, UK, Brazil, (France), Spain,

Italy, (Germ)any, Austria, Portugal, Irland, Switzerland, Netherlands, Denmark, Norway, Finland, (Czech Republic), Slovakia, (Poland), Bulgaria, Croatia, Saudi Arabia, Avustralia, South Korea, Japan

WHO, ECDC. Pai M. Int J Tubercl Lung Dis 2010 ;14: 64

Denkinger CM et al . CMI 2011; 17: 806 www.tbevidence.org

Main approaches across the guidelines

1. Two-step approach: TST first, followed by IGRA

2. IGRA only

3. Either TST or IGRA

IGRAs in the diagnosis of active TB

Meta-analysis of studies in low-and middle-income countries:

HIV (+) HIV (-)

sensitivity T-SPOT-TB %76 % 83

QFT-GIT %60 %69

specificity T-SPOT -TB %52 %61

QFT-GIT %50 %52

Metcalfe JZ et al. J Infect Dis 2011;15(suppl 4): 110

IGRAs in the diagnosis of active TB

• Meta-analysis of studies in high-and low- TB incidence countries:

T-SPOT-TB QFT-GIT

sensitivity %81 %80

specificity %59 % 79

Sester M et al. Eur Respir J 2011; 37:100

IGRAs in the diagnosis of active TB

- WHO: recommends against the use of IGRAs for active TB in low and middle income countries

STAG-TB report of the 10th meeting, WHO Geneva 2010

- ECDC: IGRAs should not replaced standard diagnostic

methods. However, in certain clinical situations IGRAs could contribute supplementary information as part of the diagnostic work-up.

ECDC guidance, Stockholm 2011

Recommendations for active TB

Denkinger CM et al. ; CMI 2011; 17:806

Specificity of IGRAs %96-100 NPV for progression to TB within 2 years T-SPOT TB %97.8 QTF GIT %99.8 PPV for progression 10% in UK ( 2/20 TB cases/IGRA+ve) 14% in Germany (6/41) 8% in Austria (3/36) 2-3% in Holland (6/181)

IGRAs in contact investigation in adults

IGRAs in contact investigation in adults

Only a few studies assessing the PPV for progression of IGRAs

- Study design varied widely the presented values are uncertain

- Low number of studies and small study populations insufficient

statistical power

Þ it is not possible to make a valid general statement

· High NPV for progression measured for IGRAs an individual with a

negative IGRA result will most likely not develop TB disease in the future

However, studies only covered a small number of individuals and were

restricted to follow –up periods of up to 2 years

Diel R ve ark. ERJ 2011; 37: 88 (TBNET/ECDC sistematic Rev & Metaan. )

ECDC guidance, Stockholm 2011

Rangaka M et al. Lancet Infect Dis 2012; 12:45

IGRA and TST were similar with the respect to the risk of TB pooled IRR : 2.11(1.29-3.46) for IGRA, 1.60(0.94-2.72) for TST IGRAs and TST have weak but similar predictive value and may not help ID those at highest risk of progression to disease

PPV for TB in IGRA positive individuals is low (5%) similar to the TST

Rangaka M et al. Lancet Infect Dis 2012; 12:45

IGRAs in contact investigation in adults

- A combination of TST/IGRA and risk factor information may be more helpful Web – based algorithm

www.tstin3d.com The online TST/IGRA Interpreter

TST size IGRA result Country of birth BCG status recent contact with active TB ConditionsÞ - PPV - risk of development of active TB after 2 years - cummulative risk of active TB up to the age of 80

Denkinger CM et al. ; CMI 2011; 17:806

Recommendations for contact investigation in adults

IGRAs in contact investigation in children

Limited data on the use for the diagnosis of LTBI in children especially in very young children

Recent meta-analyses

TST and IGRAs have similar accuracy for the detection

of TB infection or the diagnosis of disease in children Mandalakas AM et al. Int J Tuberc Lung Dis 2011; 15: 1018

Machingaidze S et al. Pediatr Infect Dis J 2011, 30: 694

Sun L et al. FEMS Immunol Med Microbiol 2011; 63: 165

Recommendations for contact investigation in children

Denkinger CM et al. ; CMI 2011; 17:806

J Acquir Immune Defic Syndr 2011; 56:230

IGRAs in Immunocompromised patients: HIV infected individuals

Sensitivity of IGRAs in HIV infected Patients with culture confirmed TB: T-SPOT-TB ( 72%) QTF-GIT (61%)· Neither IGRA was consistently more sensitive than the TST · Agreement between IGRAs and TST was higher in high-income countries

were BCG –vaccination was used less frequently IGRAs are less affected by HIV-related immunsuppression than the TST, but the differences between the tests were small

Þ IGRAs perform similarly to the TST in identifying HIV-infected individuals who could benefit from LTBI treatment

Denkinger CM et al. ; CMI 2011; 17:806

Recommendations for HIV-infected populations

IGRAs in Immunocompromised patients: individuals on TNF-inhibitor therapy

• Screening for LTBI is recommendet in many countries prior to starting TNF-inhibitors

• Only few studies have evaluated the performance of IGRAs in screening for LTBI in these patients

• No meta-analysis, two reviews: The current evidence does not suggest superiority of IGRAs over the TST in identifying latent TB in

individuals with immune-mediated inflammatory disorders

Winthrop KL et al. Int J Adv Rheumatol 2010; 8: 43 Smith R et al. Cur Opin in Rheumatology 2011; 23:377

Recommendations for persons on TNF-inhibitor therapy

Denkinger CM et al. ; CMI 2011; 17:806

IGRAs in screening of immigrants

● In low-incidence countries, a majority of the TB cases

occur among recent immigrants screening is a key

component for TB control

A World BCG Atlas has been published: www.bcgatlas.org

Zwerling A et al. PLOS Med 2011; 8: e1001012

Detailed information on current/past BCG policies/practices

for over 180 countries better interpretation of TST and IGRAs

Recommendations for screening of immigrants

Denkinger CM et al. ; CMI 2011; 17:806

The use of IGRAs instead of TST for one-time screening may result in a lower prevalence of positive tests and fewer healthcare workers who require LTBI treatment, particularly in low TB incidence settings

The use of IGRAs for serial testing optimal cut-offs?

conversions?

reversions?

Zwerling A et al. Thorax 2012; 67:62

IGRAs in serial testing of healthcare workers

Recommendations for serial testing of healthcare workers

Denkinger CM et al. ; CMI 2011; 17:806

● The use of IGRAs is increasingly recommended, primarily in low-incidence settings ● There is a considerable diversity in recommendations on how exactly IGRAs should be used ● In high-incidence and low-resource countries, the TST is still favored as there is no strong evidence that IGRAs are superior to the TST ● In low-incidence and high-resourche settings, the higher specificity of IGRAs and their logistical advantages seem to enhance their adoption and usage

● One reason for the heterogeneity among guidelines is that conclusive data to inform these guidelines were often limited

Conclusions-1

Conclusions-2

- IGRA and TST are both imperfect tests with a low predictive

value for active TB and better predictive tools are required