suzanne scheele, mehran hosseini - world health organization · suzanne scheele, mehran hosseini...
TRANSCRIPT
Ideal data sources
IncidenceAll countries should strengthen their surveillance systems until TB notifications can be
considered a direct measure or close proxy of TB incidence
The Onion” layers of missed cases
Incidence
1. SS+ incidence = SS+ notification rate / SS+ case detection rate
2.Incidence = TB mortality rate / case fatality rate
3.Incidence = point prevalence/averagedisease duration
4.SS+ incidence = ARI x Styblo ratio
Incidence
Example 1: Brasil
Incidence
Example 2: El Salvador
Incidence trend
1. Series of notifications data
2.Series of ARI surveys
3.Series of prevalence surveys
4.Series of TB mortality surveys or reliable vital registration on TB deaths over time
Incidence trend
Example 1: Brasil
Calculate the mortality rates for 2001 – 2004 in the same way that was done for 2005
Fit a line to the 2001 – 2005 mortality rates and establish the trend, which for Brazil shows a 3.3% annual decline
Apply this trend to mortality estimates for all years outside the reference year
Divide each year’s mortality estimate by the case fatality rate (held constant) to estimate incidence for each year
Series of TB mortality surveys or reliable vital registration on TB deaths over time
Incidence trend
Example 2: El Salvador
Series of notifications data
4.3% annual decline
prevalence = incidence x average duration
Prevalence
Example: Brasil
Example: Brasil
Example: Brasil
Duration of HIV- TB can vary considerably by country – our assumptions for Brazil can be seen below
Example: Brasil
Duration of HIV+ TB
We assume for all countries that the average duration of HIV+ TB is 0.5 years (6 months)
MortalityBy multiplying each disaggregated incidence rate by its corresponding case fatality rate and summing the results, we have an estimate of total mortality
Example: El Salvador
Challenging the assumptions !