1. Review of Wednesday 5th May
Workshop on
Surveillance and Epidemiology of Tuberculosis
in the Western Pacific Region
6 May 2004, Manila
Marleen Vree

2. Overview Wednesday
Lectures on direct and indirect estimates of TB burden
Exercises
Discussions
Started to work on own data

3. Direct estimates of TB burden
Prevalence of infection
Difficulties to determine which method you use to calculate prevalence of infection
Formula to calculate Annual Risk of Tuberculosis Infection
Underlying assumptions were discussed

4. Incidence of disease From ARTI to Incidence using Styblo’s rule
1% Annual Risk of infection: SS+ incidence 50 / / yr.
Situation:
stable epidemic
no control program
no HIV
Is this the case in your country?

5. Incidence of disease Incidence TB = prevalence/ duration
Prevalence survey & delay studies
= Notifications/ proportion detected
= deaths/ proportion cases dying

6. HIV-epidemic Influence of HIV on TB notification
HIV prevalence among TB cases and prevalence of HIV in adults: RR of 5
6 years delay
Where is your country in the HIV epidemic? (only in risk groups, low/ high prevalence in general population)
Can you predict what your notification rates will look like in 6 years?

7. Exercise 3 Prevalence of infection  ARTIDO
Calculated: ARTI by gender and age
Plotted: ARTI – mean calendar year
Draw lines: exponential and linear
UNDERSTAND METHODS
Why take mean calendar year?
Why transformation of data? (LN)
INTERPRETATION
Was there a decline in ARTI?
Why was there a difference between age?

8. Exercise 8 ARTI & Prevalence of diseaseDO
Calculated: ARTI by two methods (10 mm cut-off, 17 mm ‘mirror’)
Rate of decline in prevalence of disease
UNDERSTAND METHODS
What is the difference between 10 mm cut-off and 17 mm ‘mirror’?
From so many numbers in a table: why do you choose the one you choose?
INTERPRETATION
Notice how the method influence the rate of decline of ARTI
From prevalence of tuberculosis infection to ARTI to incidence of disease compare with prevalence of disease
this produces: DISCUSSION

9. Working with data: understand which data you work on
Give title to your graph:
Men/ women
Age group
Name the axis:
Prevalence/ incidence/ notification?
ARTI or LN (ARTI)
After calculating:
is your figure plausible?
For example: incidence: 5 per 10000: Did you forgot to type 0 in formula?
Is your figure plausible in relation to other figures?

10. Your data
More insight in what others have estimated for your country and understanding of assumptions
What were the assumptions?
Are these assumptions true in your country?
Or have changes taken place (recently)?
Do you have detailed information which you have not used yet?
Get more insight in your own data and the situation in your country.

11. Discuss Yesterday a lot of discussions Bring information together:
Knowledge about TB control program & health care system in a country
Knowledge about (quality of) reporting and reporting system
Knowledge about epidemiology
Knowledge about … (similar situation in other countries)
Clear eye for … (fresh look)
So… try & discuss!

12. Analysis of own data Trend in notification rates/ deaths
Best estimates in incidence, prevalence and deaths
Best estimates of case detection
SUCCESS!!!