Welcome to the I-TECH Global Health
Clinical Seminar Series
September 15, 2011
Tuberculosis Diagnostics
New Data on New Methods
Robert Martin, MS, MPH, DrPH
TB Diagnostics
New data on new methods.
Prevention of Deaths from TB
Very few would have been saved by any
diagnostic test. Specifically these deaths
occur in mainly HIV-negative people, almost
all of who die from drug-susceptible TB,
principally because of the inadequacy of
basic, inexpensive health care provision.
Carlton A. Evans
Perspective: GeneXpert-A Game-Changer for
Tuberculosis Control? PLoSMedicine 2011 Vol.8(7)e1001064
What’s New?

Stop TB Recommendations

GeneXpert MTB/RIF

Country experience – Pakistan

The future
For a disease that 8 million will acquire
each year, why are we still using
methods developed in the late 1800’s?
1. Populations that TB affects
2. Low prevalence (comparatively) in developed
countries.
3. Rigorous (costly) regulatory standards in
developed countries, so no incentive for
manufacturers to develop new low-cost assays.
What is new?
The Global Plan to Stop TB
2011 - 2015
•Laboratory strengthening – included as a
major component.
•Fundamental research and operational
research
•Up-to-date epidemiological predictions.
•Updated targets for TB care and for research
and development.
•Updated funding requirements.
Estimated Funding to
Implement Global Plan
 Laboratory Strengthening – $4 billion
 New Diagnostics - $1.7 billion
 Fundamental Research – $2.1 billion
 New Drugs - $3.7 billion
 New Vaccines - $1.9 billion
Bridging the gap:
LED-based Fluorescence Microscope
Liquid culture media
Endorsed by WHO, 2007
Line probe assay
Serologic Assays?
WHO Recommended
Levels of Service
WHO levels
New Molecular
Technologies?
Recommended
Services
Culture/DST
EQA
Training
Microscopy
Many resourcelimited countries
Culture/DST
Microscopy
EQA/Training?
Intermediate Laboratory
Culture/DST
EQA
Training
Microscopy
Microscopy
Peripheral
Laboratory
Microscopy
Microscopy
Central Laboratory
The Game Changer?
On 8 December 2010 the World
Health Organization (WHO) endorsed
the Xpert MTB/RIF assay.
GeneXpert
High tech in low tech settings: XpertTM MTB
GeneXpert
Automated Sample Prep,
Amplification and Detection
<120 minutes
2008
Development Evaluation in 5 trial sites
2010
2009
Demonstration
in 15 microscopy centers
STAG Access
Challenges downstream:
Meeting the target price
A technology platform:
 TB & Rif Resistance
 Potential for HIV viral
load
 Potential for …
Recent Publications Addressing
GeneXpert MTB/RIF Testing



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Boehme CC, Nicol MP, Nabeta P, et al. Feasibility, diagnostic accuracy, and
effectiveness of decentralized use of the Xpert MTB/RIF test for diagnosis of
tuberculosis and multidrug resistance: a multicentre implementation study.
Lancet 2011. April 30, 377(9776):1495-1505.
Helb D, Jones M, Story E, et al. Rapid Detection of Mycobacterium tuberculosis
and Rifampin Resistance by Use of On-Demand, Near-Patient Technology. JCM
2011 v48(1).
Vadwai V, Boehme C, Nabeta P, et al. Xpert MTB/RIF: a New Pillar in Diagnosis
of Extrapulmonary Tuberculosis? JCM 2011. V 49(7)p.2540-5.
Comparison of Xpert MTB/RIF with Other Nucleic Acid Technologies for
Diagnosing Pulmonary Tuberculosis in a High HIV Prevalence Setting: A
Prospective Study. Scott LE, McCarthy K, Gous N, et al. PloS Medicine 2011.
V8(7)e1001061.
Dowdy D, Cattamanchi A, Steingart KR, Pai M. Is Scale-Up Worth It? Challenges
in Economic Analysis of Diagnostics Tests for Tuberculosis. PLoS Med
8(7):E1001063/journal.pmed.1001063
Methods/Results (Boehme et al.)




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Population - 6,648 adults >18 years of age (1,033
culture positive)
One-off testing
MTB/RIF detected more than 90% of patients with
positive cultures (90% sensitivity, 99% specificity)
MTB/RIF test sensitivity was 76.9% in smearnegative, culture-positive patients (296 of 385)
Smear microscopy (2-3 examinations per patient)
detected 67.1%
Results
 Correctly identified 242 of 250 rifampicin
resistant TB (96.8% sensitivity)
 Correctly identified 779 of 810 rifampicinsensitive cases (96.2%)
 With modified software, decreased sensitivity
to 94.4% and increased specificity to 98.3%
Results
 Of 153 patients with clinically diagnosed TB
and negative culture, 24 (16%) had a positive
MTB/RIF– 20 of 24 (83%) improved on
treatment.
Proportion of tuberculosis cases detected by each method in culture-positive patients
Percentages are the maximum proportion of cases detected by every method. (A)
Tuberculosis case detection. (B) Detection of rifampicin resistance. Time to detection was
defined as time between date of sputum sample collection and date of positive result.
MTB=Mycobacterium tuberculosis. RIF=rifampcicin.
Boehme CC, Nicol MP, Nabeta P, et al. Feasibility, diagnostic accuracy,
and effectiveness of decentralized use of the Xpert MTB/RIF test for
diagnosis of tuberculosis and multidrug resistance: a multicentre
implementation study. Lancet 2011, published online April 19.
DOI:10.1016/S0140-6736(aa)60438-8.
Issues for Small Health Centers
 Stable electricity
 Equipment should not be operated in
environments >30C
 Cartridges stable at 2-28C
 No data for use in dusty or humid conditions
 Requires annual calibration
 Need studies to evaluate the impact of early
detection (cost effectiveness?).
Results – Analytic and Validation
Study Vietnam (Helb et al.)
 Clinical limit of detection – 131 CFU/ml in
sputum
 In small validation study of 107 sputum
samples from Vietnam
 Detected 29/29 (100%) smear +, culture+
 Detected 33/39 (84.6%) smear -, solid culture+
 Detected 38/53 (71.7%) smear -, liquid culture+
Results – India (Vadwai et al.)
Extrapulmonary Specimens




547 extrapulmonary specimens (biopsy, pus, body
fluids, CSF)
Reference standard a composite of smear & culture
results and clinical, radiological and histological
findings.
Culture – 53% (150/283) sensitivity
MTB/RIF – 81% (228/283) sensitivity
 Lowest (29%) sensitivity in CSF samples
 64% (89/138) in smear-negative
 96% (139/145) in smear-positive
Results – Comparison with Other NAT
in a Prospective Clinical Validation
South Africa (Scott et al.)
 311 participants; 70% (215/311) HIV prevalence;
38.5% (120/311) culture positive TB

Sensitivity when compared to liquid culture
 Smear + –
59%
Smear Negative
 MTBDRplus – 76%
28%
 LCTB –
76%
22%
 MTB/RIF –
86%; in HIV + - 84%
61%
 Specificities all >97%
Results – Comparison with Other NAT
in a Prospective Clinical Validation
South Africa (Scott et al.)

Sensitivity when compared to clinical definition
 Smear + –
40%
 MTBDRplus – 51%
 LCTB –
51%
 MTB/RIF –
58%
GeneXpert – A Game-Changer
for Tuberculosis Control?
C.A. Evans PLoS Medicine July 2011 Vol 8 Issue 7
 Intermediate Sensitivity – Better than
microscopy, less than broth culture.
 A single MTB/RIF test detected less than half of
cases of smear-neg, culture-pos TB in HIV-positive
patients
 False resistance
Issue: Benefits of increased correct diagnoses
with adverse consequences of occasional
misdiagnoses.
GeneXpert – A Game-Changer
for Tuberculosis Control?
C.A. Evans PLoS Medicine July 2011 Vol 8 Issue 7
 Improved Accuracy
 Requires access to confirmatory culture-based
testing.
 May increase demand for specialty reference
laboratories and/or their services (e.g., BSL3).
 If RIF resistant, immediate implications for the
need for DST to second line drugs (? increased
demand for specialty reference laboratories).
Outcomes from the Global
Consultation
•
Agreement on interim diagnostic algorithms prepared by Working Groups.
•
Agreement to pursue Xpert MTB/RIF roll-out in a systematic and coordinated
programmatic approach in a so-called ‘Evidence for scaling-up’ phase during
2011.
•
Development of a ‘Rapid Implementation’ document to guide Xpert MTB/RIF
roll-out in the ‘Evidence for scaling-up’ phase.
•
Monitoring of global sales and market dynamics by FIND
•
Establishment of a post-marketing surveillance programme by FIND
•
Organization of an Early Implementers’ Meeting in December 2011
to share experiences.
Beyond Implementation of Technology




How to best implement to improve patient care.
Who should receive limited capacity for better tests.
How will these tests impact patient-relevant
outcomes.
How will these issues vary among settings (e.g., will
suspect TB cases who are smear negative require
MTB/RIF test?)
Is Scale-Up Worth it?



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Addressed each of four possible test results.
Pointed out that studies generally enrich the
population with disease (e.g., high prevalence).
Predictive value is high with a low number of false
positives.
Costs of false-positives often underestimated.
Costs of scale-up could divert resources from more
cost-effective interventions (e.g., access to highquality microscopy)
Is Scale-Up Worth It? Challenges in Economic Analysis of Diagnostics
Tests for Tuberculosis. Dowdy D, Cattamanchi A, Steingart KR, Pai M.
PLoS Med 8(7):E1001063/journal.pmed.1001063
Example: India
 Providing Xpert MTB/RIF at current prices to
15% of all TB suspects would consume the
entire budget of the National TB Program
($65M).
Implementing Xpert MTB Rif
diagnostic assay in Pakistan
Operational Issues
WHO Recommended
Levels of Service
WHO levels
New Molecular
Technologies
Recommended
Services
Culture/DST
EQA
Training
Microscopy
Many resourcelimited countries
Culture/DST
Microscopy
EQA/Training?
Intermediate Laboratory
Culture/DST
EQA
Training
Microscopy
Microscopy
Peripheral
Laboratory
Microscopy
Microscopy
Central Laboratory
Piloting of GeneXpert in Pakistan
Objective :•
Pilot test diagnostic algorithm for early
diagnosis of MDR and smear negative TB
with use of GeneXpert at 12 sites .
• Financial support : US (DOS)
Xpert Implementing sites – laboratory
workload
Recommendation
• 10-20 samples a day or 2000-4000 annually from
high risk group
Issues and challenges
• Expected samples from high risk group in
implementing sites is much lower
Solution
• Referral linkages and specimen transport to
ensure optimal efficiency
Selection of individuals to Test
HF with AFB microscopy + Xpert
Xpert-Import
• Tax exemption from central board of revenue
• Custom clearance
Xpert – Central storage of Kits
Recommendation :
Temperature for storage of kitS 2-28C
Issue/challenges
• Lack of cold storage space for kits
Solution
• Request to EPI(extended Programme for
immunization) for storage of KITS
Xpert Implementation –Infrastructure
Recommendation/Requirement
uninterrupted and stable electrical power supply .
Issues /challenges
• Xpert with UPS having 15 min back up only
• Severe power crises with long hours of power failures is
common
• Only 5/12 proposed sites has generator back up –but
generator output is not stable .
Solution
• Power supply stabilizers and UPS with 2hours battery
back up.
Xpert Implementing sites – Ambient
temprature
Recommendation
• ambient temperature not to exceed 30C
Issues and challenges
• Temperature exceeding 40c in summers is usual
across country
Solution
• Air conditioners for all installation site
Xpert Implementing sites – storage of
kits
Recommendation
• Storage of KITS 2-28C
Issues and challenges
Enough refrigerators not available
Solution
• Dedicated refrigerator (freezer less) for
storage of KITS
Xpert Implementing sites – laboratory
worload
Recommendation
• 10-20samples a day or 2000-4000 annually from
high risk group
Issues and challenges
• Expected samples from high risk group in
implementing sites is much lower
Solution
• Referral linkages and specimen transport to
ensure optimal efficiency
Workshop for Early Implementers
Chateau du Penthes, Pregny-Chambésy (Geneva), Switzerland
7 - 8 April 2011
Meeting Objectives
• To provide country health programmes and their local and international technical
partners with the science behind Xpert MTB/RIF, assay performance characteristics
and the need to link diagnosis with treatment and care in different epidemiological and
resource settings;
• To discuss with countries and partners the practical considerations for roll-out of
Xpert MTB/RIF using the WHO Implementation Document, including interim
diagnostic algorithms, patient management approaches, and key data elements to be
collected to inform future scale-up;
• To map country and technical partner plans for roll-out of Xpert MTB/RIF in order to
maximize resources and avoid duplication and overlap.
Other New Developments
 WHO Policy/Recommendations
 The Pipeline for New Technology
The Lancet, Volume 377, Issue 9760, Pages 113 - 114, 8 January 2011
WHO recommends against inaccurate tuberculosis tests
The available evidence indicates that current tests lack either the
necessary sensitivity or specificity or both to be an effective
diagnostic test, and for many of these tests, false results far
outnumber true results.
WHO Diagnostic Evaluation No. 2 - Laboratory based evaluation of 19 commercially
available rapid diagnostic tests for tuberculosis
Why Are Serological Tests
for TB Inaccurate?
From WHO Diagnostic Evaluation Series No. 2
 Heterogeneity of host immunological
responses to TB antigen.
 The profile of antigenic proteins of MTB
recognized by antibodies differs at different
stages of infection and disease progression.
 Thus, an accurate diagnostic test for TB will
almost certainly need to be based on a
combination of antigens.
Rapid Methods for Identification
and Susceptibility Testing
Alternatives to liquid or solid culture – MODS, Thin
Layer
Rapid DST testing from culture (e.g., Capilla, Reazurin
Microtiter Assay)
Molecular testing methods for identification of TB and
DST (e.g., Hain Geno Type, INNO-LiPA RifTB)
Challenges to all of these in resource limited settings
(e.g., minimum requirements to establish a successful
molecular testing facility)
Possible changes in biosafety
requirements being considered by WHO?

Possibly three levels under consideration dependent
on risk
 Low – Preparing smears or preparing GeneXpert
cartridges.
 Moderate – culture, DST (manipulation in BSC
class I or IIA, room ventilation with 6-12 air
exchanges/hour, PPE (glove recommended,
gowns, respirators not required, restricted access,
training to minimize aerosols.
 High – XDRTB (manipulation performed in BSL4)
Progression of Development of
TB Diagnostics
http://www.tbevidence.org/tbdxpl.htm
Lessons learned
Political will and commitment
Ensure a reliable supply of reagents and
supplies
Sustainability requires integration into a national
laboratory policy and into strategic plans
Conclusion
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New interest in laboratory strengthening.
Exciting and promising new laboratory technologies – improved
sensitivity.
Must keep in mind that technologies are replaced quickly – is the
future a POC NAT or POC antigen or antibody (or both)
detection test?
However, GeneXpert (or any new technology):
 implementation in the field (where) and how it will be used
(algorithm) will be critical learning experiences.
 to be cost-effective, good clinical judgment is required as well
as quality assured smear-microscopy. A referral system for
transfer of specimens to a reference laboratory for DST will
still be necessary.
 economic evaluations in each country will be an important
consideration.
Thank You
Robert Martin, MPH, DrPH
University of Washington
RMartin1@uw.edu
Thank you!
Next session: Oct 27, Case
Consultations: HIV
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Welcome to I-TECH HIV/AIDS
Clinical Seminar Series
Next session: October 27
Case Consultations: HIV
Chris Behrens MD, Shireesha Dhanireddy MD,
Robert Harrington MD and Christian Ramers MD
MPH