Philippe Glaziou Geneva, 12 October 2009 A new perspective on TB disease burden and TB control in Viet Nam Lessons from a prevalence survey Philippe Glaziou Geneva, 12 October 2009

The problem with case detection rates CDR not directly measurable Optimal TB surveillance systems capture almost all incident cases If surveillance is suboptimal, then what is directly measurable? Prevalence (survey) Mortality (vital registration) Diagnosed patients: inventory studies Mapping of providers Size of diagnosed but not notified TB population

High case detection and treatment success but no decline in notifications in Vietnam: Why?

Prevalence survey showed prevalence much higher than previously thought Prevalence rate per 100,000 Prior estimate (WHO) Survey, 2006-7* [95% CI] Smear (+) 86 145 [110 - 180] Bacteriologically confirmed 226 [183 - 269] *Source: Prof Sy. Report of the National TB Prevalence Survey in Vietnam, 2006-7

Estimating the case detection rate from a prevalence measurement CDR = N/P / (N/P + 1/d) [1] d denotes the average duration of disease Duration: triangular distribution from 1 to 4 years, mode at 2 years (EV = 2.3) Prevalence: normal distribution around point prevalence estimate from the survey, s.e. adjusted for sampling design [1] Borgdorff M. New measurable indicator for tuberculosis case detection. EID 2004; 10(9): 1523-1528

Case detection rates in 2007

Chronic cough lacks sensitivity, importance of relapses Only 53% of prevalent sputum smear positive cases reported chronic cough 22% of ss(+) cases previously treated for TB (8-month regimen used in past) 36% more than 2 years before 64% recently, 63% of them successfully Sex ratio (M/F) = 4.5 (bacteriologically confirmed cases)

Private providers 8% of 326 suspects with history of TB treatment were treated in the private sector PPM intervention project (HCMC) +18% notifications in PPM districts over 1 year (-1% in other HCMC districts) Internal migrants moving to cities tend to access care from the private sector

In-depth analysis of surveillance data Decline in notifications in older age groups, increase in young adults

Lessons learned Disease burden higher than previously thought: keep TB high on the political agenda Notifications estimated to reflect trends in incidence, declining at an age standardized rate of -2%/yr, but increasing in 15-24 yr-old group Importance of accounting for changes in demographic structure Large pool of unreported cases in private sector PPM, link with hospitals Electronic recording and reporting Improve screening, expand active case finding

Conclusions Prevalence surveys provide robust measurement of national coverage and impact of TB control Combined with in-depth analysis of surveillance data, survey results help understand and interpret epidemiological patterns and trends update policies on TB screening and care improve reporting address the needs of at-risk populations