The role of prevalence surveys in measuring the burden of TB,
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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. Content. Background Task Force recommendations

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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


Content TB,

  • Background

  • Task Force recommendations

  • What is needed to implement a survey and what can surveys tell us?

  • Current status of survey implementation

  • Next steps


Background TB,

  • 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  • Estimation of TB burden using tuberculin surveys no longer applicable in most settings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



Countries where surveys are recommended
Countries where surveys are recommended TB,

21 global focus countries

36 additional countries that met basic criteria


How should surveys be implemented
How should surveys be implemented? TB,

Follow the guidelines!


Recommended screening strategy
Recommended screening strategy TB,

Do smear and culture at least for with TB symptoms and/or abnormal chest X-ray




What is required for a survey? TB,

  • 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



Survey day TB,

Transport people to X-ray site


Individual interview by trained health professional from central unit
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 spot quality direct x ray is available in villages
Develop and read images on the Spot central unitQuality Direct X-ray is Available in Villages

that contributed to high participation rates and 100% sputum collection from suspects


Prevalence survey in viet nam
Prevalence Survey in Viet Nam central unit

Digital technology was introduced for the first time to National Scale TB survey


Lab work central unit

Smear Microscopy

Direct Smear, ZN

LED-FL

Collect, Store, Transport and Put in Culture within 5 days



A carefully designed survey can tell you lots more than tb prevalence
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


Re-estimation of TB Burden prevalence

  • 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


Strategies for screening tb suspects
Strategies for screening TB suspects prevalence

40-60% of confirmed cases in surveys do not have chronic cough

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


Smear microscopy alone misses 50 of bacteriologically confirmed tb
Smear microscopy alone misses >50% of bacteriologically-confirmed TB

*Africa 5 sub-national surveys average


Where are cases being missed
Where are cases being missed? bacteriologically-confirmed TB

Yangon survey, 2006: 1/3 of TB patients being treated by GPs

33 in NTP: around 130/100,000 = 260/100,000/year


Current status of survey implementation bacteriologically-confirmed TB


Good progress in asia
Good progress in Asia bacteriologically-confirmed TB


No survey in africa started yet urgent action required
No survey in Africa started yet – urgent action required!! bacteriologically-confirmed TB

HBC

Other countries preparing: Ghana, Malawi, Mali, Rwanda, Togo, Zambia,


Next steps bacteriologically-confirmed TB


Workshop on prevalence surveys in 12 african countries 15 16 october 2009
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


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