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The role of prevalence surveys in measuring the burden of TB,
progress in TB control and improving early case detection
Ikushi Onozaki
WHO/STB/TBS
Global Task Force on TB Impact Measurement
DEWG meeting, Oct 13-14 2009, Geneva
Background
Task Force recommendations
What is needed to implement a survey and what can surveys tell us?
Current status of survey implementation
Next steps
Content
TB prevalence is an MDG indicator that can be directly measured in HBCs
Estimation of TB burden using tuberculin surveys no longer applicable in most settings
Funding is available for surveys, and governments and international agencies recognize importance of measuring impact
Background
Task Force recommendations
Countries where surveys are recommended
21 global focus countries36 additional countries that met basic criteria
How should surveys be implemented?
Follow the guidelines!
Recommended screening strategy
Do smear and culture at least for with TB symptoms and/or abnormal chest X-ray
What is needed to implement a survey?
( WHO headquarters, March 2008)
Sample size : 30,000- 60,000
Cluster size: 500-1,000
12-15 staff per field team for 6–10 months, 3-4 team operation
Costs ~ US$1 million in Asia, US$2 million in Africa Capital investment (CXR, Lab, Cars), Human Resource (Salaries), Survey Operation (Field and Central), Pre & Post survey events, technical assistance
What is required for a survey?
Go to the community
Survey day
Transport people to X-ray site
Individual interview by trained health professional from central unit
• TB related symptoms
• TB history– Possible treatment– Consultation Places
• Risk factors
Develop and read images on the SpotQuality Direct X-ray is Available in Villages
that contributed to high participation rates and 100% sputum collection from suspects
Prevalence Survey in Viet NamDigital technology was introduced for the first time to National Scale TB survey
Smear Microscopy
Direct Smear, ZN
LED-FL
Collect, Store, Transport and Put in Culture within 5 days
Lab work
What can be learned from a survey?
A carefully designed survey can tell you lots more than TB prevalence
• Changes in TB burden and re-estimation of burden
• Performance of strategies for screening of TB suspects
• Health-seeking behaviour of TB patients and individuals reporting chest symptoms
• Where and why are cases missed by the NTP e.g. access to care, role of private sector
• Risk factors
•Prevalence of Sm+ TB in Cambodia, 2002, was half of previous estimate and previous study results
•Prevalence of S+ in Yangon, Myanmar, nearly 3 times previous national estimate -> National Survey
•Prevalence of S+ in Viet Nam, 2007, was 60% more than previous estimate
Prevalence Surveys can help to revise and improve estimates of disease burden and CDR
Re-estimation of TB Burden
Strategies for screening TB suspects
No Chronic Cough No symptomS+ Bac + Bac +
Cambodia 38% 61% 15%
Zambia 57% 10%
Viet Nam 40% 45% 25%
NTP Cambodia. National TB Prevalence Survey Report, 2002. 2005, ** H Ayles et al. Plos one May 2009. e 5602, *** NTP Viet Nam. Presented in UNION APR Conference, Beijing, Sept 2009
40-60% of confirmed cases in surveys do not have chronic cough
Smear microscopy alone misses >50% of bacteriologically-confirmed TB
*Africa 5 sub-national surveys average
S+/ Bac+Cambodia 2002 30%
Philippines 2007 43%
Korea 1995 41%
Africa* 01- 05 34%
Where are cases being missed?
64 participants were on TB treatment
52%
34%
9%5%
NTP 33
GP 22
Other 6
Unknown 3
33 in NTP: around 130/100,000 = 260/100,000/year
Yangon survey, 2006: 1/3 of TB patients being treated by GPs
Current status of survey implementation
Good progress in Asia
Completed Next Protocol Budget
Cambodia 2002 2010 Finalizing Almost secured
China 2000 2010 Finalizing ditto
Philippines 2007 2017? (disseminating)
Viet Nam 2007 2012 (disseminating)
Completed Next Protocol Budget
Bangladesh 2009 ? Analyzing
Indonesia 2004 2012? To be proposed
Myanmar (1994) 2009 (Ongoing) Secured
Thailand (1991) 2011 Drafting Secured
Pakistan (1987) 2010 Final draft Secured
No survey in Africa started yet – urgent action required!!
Completed Next Protocol Budget Ethiopia - 2010 Final draft Almost secured Kenya - 2010 Final draft Applied Mozambique - Feasibility assessment Nigeria - 2010 Final draft Partially secured South Africa - 2010 Revising National budget Tanzania - 2010 Finalized Partially Uganda - 2010 Reviewed Partially
HBC
Other countries preparing: Ghana, Malawi, Mali, Rwanda, Togo, Zambia,
Next steps
Workshop on prevalence surveys in 12 African countries, 15-16 October 2009
• Identification of bottlenecks holding up survey implementation
• Lessons from Asia
• How to solve the bottlenecks
• Role of Task Force partners in providing technical assistance to countries