TB in children: still a difficult task for the clinician? Beate Kampmann MD FRCPCH PhD A/Professor in Paediatric Infection & Immunity Consultant Paediatrician Imperial College London, UK and Themeleader Vaccinology MRC-The Gambia

Overview What is special about TB in children? Epidemiology- who are our patients? Diagnostic challenges: - Differences between adults and children - New Immunological Tools-how helpful are they? Therapy: Drugs in kids- any differences? Prevention: new TB vaccines on the horizon

Tuberculosis in Children…. the problem Significant Morbidity and Mortality 1.4 million cases annually (95% developing countries) 450,000 Deaths estimated 10-15% of global burden related to childhood TB Different clinical spectrum of disease 5-10% < 2 yr meningitis disseminated disease more common Co infection with HIV- clinically very difficult to distinguish Remains a diagnostic challenge paucibacillary, rarely culture confirmed : Sputum smear positive in 10.3% (10-14yr), 1.8% (5-9) and1.6% (<5) Cultures positive 21% (10-14), 5% (5-9) and 4.2% (<5),

Tuberculosis in Children differs from adults Immune responses are Age-dependent: Following infection 40% < 2 yr, 25% 2-5 yr and 5-15% of older children will develop disease within 2 years Majority of disease results from progression of primary infection rather than reactivation might affect detectable immune responses More likely to be extrapulmonary and disseminated, particularly in infants Newton, Kampmann The Lancet Infectious Diseases, August 2008; Vol 8:

Tuberculosis in the UK: ca cases in % in London

Percentage of TB cases of foreign origin, 2006 Andorra Malta Monaco San Marino Not included or not reporting to EuroTB 0% – 4% 5% – 19% 20% – 49% > 49% Trends in incidence of TB in children under 15 years by ethnic group in London,

UK: Tuberculosis rates by age Sources: Enhanced Tuberculosis Surveillance, Labour Force Survey population estimates, Abubakar et al Arch. Dis. Child. 2008;93; ; Development of TB in immigrant children

Is the general population at risk of disease from affected migrants? Little evidence to suggest that the wider population are at significant risk Source, Enhanced Tuberculosis Surveillance Tuberculosis rates by place of birth:

Children acquire TB from (household) contacts If you ask yourself, does this child have TB, ask yourself: is there TB in this family?

Presentation of PAEDIATRIC TB Case month Asian girl -previously well, no F/H of TB -3 weeks cough and unwell -admitted to local hospital -low grade fever -normal chest examination WHAT INVESTIGATIONS WOULD YOU DO?

PAEDIATRIC TB Case 1 Mantoux test: 2mm Gastric washings; - microscopy and (later) culture negative -Rx.Erythromycin and Augmentin -no improvement on antibiotics -bronchoscopy planned

PAEDIATRIC TB Case 1 1 day before bronchoscopy: - afebrile, less cough, looking well -continued improvement, - discharged home, no ∆

PAEDIATRIC TB Case 1 out-patient review 6 weeks later: -completely well, thriving, no cough “Grandfather admitted to local hospital with pulmonary TB” -repeat Mantoux: now 25mm -TB treatment commenced

PAEDIATRIC TB Case 1 Discussion Points Primary TB in children: - spontaneous recovery is possible - diagnosis is difficult - no visible AFB - cultures usually negative - tuberculin test negative - F/H is often the clue to diagnosis

CHILDHOOD EXPOSURE PRIMARYPULMONARYINFECTION WELLADULT IMMUNITY (live MTB) Successfulimmuneresponse LATE REACTIVATION OF PULMONARY DISEASE FORMSCAVITY

CHILDHOOD EXPOSURE PRIMARYPULMONARYINFECTION PROGRESSIVEPULMONARYDISEASE MILIARY TB or EXTRA-PULMONARYDISEASE Inadequateimmuneresponse Lympho/haematogenousspread Self healing??

L Wyld Aug 2010 Miliary TB

Diagnostic tests Microbiological Organism smear culture DNA

Appearance in sputum Appearance in culture ‘cording’ The “gold-standard”

Paediatric TB: 10 6 bacteria Adult TB: >10 9 bacteria - children less infectious - difficulty in confirming diagnosis - difficulty in detecting resistance PAEDIATRIC TB: Implications of bacterial load

Diagnostic tests Immunological Host response skin test antigen-specific production of IFNγ

What are IGRA and why do we need them How do they work What do they contribute to the diagnosis of active or latent TB What do they contribute to the diagnosis of active or latent TB Performance in the immunocompromised Remaining research questions Conclusions Acknowledgement & Thanks IGRA in children

Paediatric TB: 10 6 bacteria Adult TB: >10 9 bacteria Paediatric TB: 10 6 bacteria Adult TB: >10 9 bacteria children less infectious children less infectious lack of “gold standard”: microbiological confirmation exceptional lack of “gold standard”: microbiological confirmation exceptional difficulty in detecting resistance difficulty in detecting resistance Acknowledgement & Thanks Paediatric TB: Diagnostic challenges due to low bacillary load

technically difficult in children UK: 2 units of SSI tuberculin (PPD) > 200 antigens, incl. BCG Ag Read-out: degree of hypersensitivity Problem: lacks specificity and sensitivity Acknowledgement & Thanks Tuberculin skin test (TST)

Antigens used: ESAT-6 CFP10 +/- TB7.7 mitogen negative control In principal: can both distinguish between BCG vaccination and M.tuberculosis infection but: Paucity of data in children Confusion about use of IGRA Acknowledgement & Thanks 2 commercially available assays

M. tuberculosis M. bovis 4/5 deletions 30/40 genes 10 deletions 64 genes BCG substrains RD1 region major antigens ESAT6 and CFP10 T cell tests (interferon-γ) that distinguish M. tuberculosis infection from BCG vaccination Acknowledgement & Thanks Gene deletions and the origin of BCG

AG presentation (ESAT-6, CFP-10, TB7.7) Ag-specific cytokine secretion Cytokine quantification by ELISA Principal of Quantiferon-Gold in tube assay

Coating antibody PBMC+antigen IFN-  production Biotinylated 2 nd antibody Avidin-peroxidase each spot is an antigen-specific T cell that has released IFN  Principal of ELISPOT assay

UK: NICE Guidelines IGRA and National TB guidelines

Acknowledgement & Thanks IGRA and the diagnosis of active TB Travel Active TB Signs and symptoms Radiology Microbiology TST Contact history IGRA

Spot the Difference Interferon-  release assays (IGRA) in paediatric active and latent tuberculosis in London - a side-by-side comparison with TST Kampmann B, Whittaker E, Williams A, Walters S, Gordon A, Martinez-Alier N, Williams B, Crook AM, Hutton AM, Anderson ST. Interferon- gamma release assays do not identify more children with active TB than TST. Eur Respir J Jun;33(6): IGRA versus TST: our own research

IGRA missed between 20-40% of definite active TB Acknowledgement & Thanks IGRA and the diagnosis of active TB

A combination of TST and IGRA increases sensitivity to above 93% Acknowledgement & Thanks Combining IGRA and TST in the diagnosis of active TB

Acknowledgement & Thanks IGRA and the diagnosis of active TB- other studies Bamford et al, Arch Dis Child 2009 Oct 8 (Epub ahead of print) UK-wide study of 333 children from 6 large UK centers, 49 with culture-confirmed TB: TST had a sensitivity of 82%, Quantiferon-Gold in tube (QFT-IT) had a sensitivity of 78% and T-Spot.TB of 66%. Neither IGRA performed significantly better than a TST with a cut-off of 15 mm. Combining results of TST and IGRA increased the sensitivity to 96% for TST plus T-Spot.TB and 91% for TST plus QFG-IT in the definite TB cohort. Connell et al, Thorax 2006, Jul;61(7): The whole blood IFN-gamma assay was positive in all 9 children (100%) with TB disease. Bianchi et al, PIDJ 2009, Jun;28(6):510-4 IGRA was positive in 15 of 16 (93.8%) children with active pulmonary TB Nicol et al; Pediatrics 2009,Jan; 123(1): Comparison of T-SPOT.TB assay and TST for the evaluation of young children at high risk for tuberculosis Sensitivity of the T-SPOT.TB was no better than that of the tuberculin skin test (>10mm) for culture-confirmed tuberculosis (n=10) (50% T-Spot and 80% TST) and was poorer for the combined group of culture-confirmed and clinically probable tuberculosis (n=58) (40% T-Spot and 52% TST).

A negative IGRA does not exclude active TB IGRA is not a rule-out test, but can add value to additional investigations Acknowledgement & Thanks IGRA and the diagnosis of active TB

Acknowledgement & Thanks IGRA and the diagnosis of latent TB Travel/Immi gration Latent TB negative Radiology TST Contact history Absence of clinical signs and symptoms IGRA

No “gold standard” for LTBI Acknowledged discrepancy of TST and IGRA results - due to poor specificity of TST (Kampmann ERJ 2009, Connell PlosOne 2008, Bianchi PIDJ 2009) Which IGRA is better? - Good agreement between 2 IGRAS (92%, k=0.82) (similar to Connell et al, PLoS One Jul: agreement between QFT-IT and T-SPOT.TB 93%, k=0.83). Currently: ? “over-treatment” by paediatricians -but: to date no studies of negative predictive value of IGRA in children Performance in very young children- conflicting messages Increased sensitivity in immuno-compromised hosts IGRA and the diagnosis of latent TB

Detection of tuberculosis in HIV-infected children using an Elispot Davies et al, AIDS May 15;23(8): ELISPOT was positive in 14/21 (66%) with definite TB ELISPOT was more sensitive than TST for the detection of active TB in HIV-infected children: positive ELISPOT compared with a positive TST [25/39 (64%) vs. 10/34 (29%), P = 0.005] “However, the sensitivity of current ELISPOT assays is not sufficiently high to be used as a rule out test for TB.” High level of discordant IGRA results in HIV-infected adults and children Mandalakas et al: Int J Tuberc Lung Dis Apr;12(4): Mandalakas et al: Int J Tuberc Lung Dis. Active TB Latent TB HIV+ve children (n=23): tests yielded discordant results 61% of individuals testing positive with T-SPOT.TB, 41% with TST and 28% with QuantiFERON TB Gold (QTF)- older version IGRA in the immuno-compromised host

Newly diagnosed HIV or new immigrant with HIV IGRA at baseline positivenegative Investigate for active TB Active TB TB Tx Latent TB chemopro ? Immune system - check PHA ? Lack of exposure /no infection Repeat IGRA when “immune reconstituted” Use as baseline result if concerns of active TB arise later Algorithm for use of IGRA in HIV+ve patients

Reliability of performance of IGRA in very young children How do we interpret indeterminate results Negative predictive value, i.e. How many children will develop active TB if TST > 15 mm, but untreated with chemoprophylaxis as IGRA negative, according to current guidelines Is the step-wise approach of TST first, IGRA second justified? How many children with negative TST would have a positive IGRA at screening Does the TST boost the IGRA responses Current evidence suggests that boosting occurs, but not within first 72 hours (Short-term) reproducibility of the commercial IGRA Can IGRA be used to monitor therapy or to predict development of active TB Should we abandon the TST in screening for LTBI ? Remaining questions and further research

IGRA detect immune memory but do not confirm the presence or absence of M. tuberculosis- active or latent higher specificity than the TST designed to test for evidence of TB infection, not TB disease can be used as a rule-in test for active TB in children, but not as a rule-out test higher sensitivity in immunocompromised patients compared to TST IGRA should not currently replace the TST in children we should not forget the many additional challenging question in childhood TB Conclusions better microbiological diagnostics better biomarkers than IFN  better vaccines improved understanding of primary TB

Diagnosis of TB in children Poor microbiology Suspicion rather than confirmation Treatment dilemma

TB treatment in children Treatment regimens are adopted from adult schemes Children respond very well to treatment, incl DOTS Dosages need to be adjusted for weight Pharmakokinetics in children differ from adults - INH mg/kg, rapid acetylators (1) - Ethambutol mg/kg (2) 1: Schaaf et al, Arch Dis Child 2005; 90:614 2: Donald et al, Int J Tuberc Lung Dis 2006; 10:1318

IF YOU DON’T TAKE THE DRUGS, THEY WON’T WORK Drugs and ADHERENCE

PAEDIATRIC TB POOR ADHERENCE Support -hospital TB clinic -community -health care workers -social services -DOT (Directly Observed Therapy) -accurate record of treatment -successful treatment -prevention of resistance -different adult -different location

L Wyld Aug 2010

New vaccines on the horizon Four main types of vaccines are currently under development: 1.Vaccines based on BCG 2.Subunit (protein and peptide) vaccines 3.DNA vaccines 4. Live attenuated and inactivated whole cell vaccines E.Whittaker & B.Kampmann, Vaccines in Practice, 2011

Take Home messages: Think of the diagnosis, especially in the epidemiological context TB is a family disease The diagnosis of active TB in children is based on a jigsaw of findings IGRA can be an additional piece in the jigsaw, but a negative IGRA does not exclude active TB TB therapy needs a lot of support Comprehensive review of childhood TB in Paediatric Resp Rev 2010

founded in April 2009 to date: 35 members from 16 European countries, incl. Eastern Europe includes clinicians, epidemiologists and laboratory scientists Aims enhance the understanding of the pediatric aspects of tuberculosis facilitate collaborative research studies for childhood TB in Europe provide expert opinion through excellence in science and teaching establish a better evidence base for diagnosis and treatment of TB in children

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