Using data to make decisions at the local level
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The strategic drivers to eliminate trachoma at the local level are based on data.
Data is used to:
- Know where, and how big, the problem is.
- Develop an appropriate Trachoma Action Plan at a national level.
- Advocate with local stakeholders.
- Ensure resources (both human and infrastructure) and finances are appropriately allocated at district level.
- Track and monitor SAFE implementation against a timeline.
- Assess the outputs and achievement of elimination targets through further surveys.
World Health Organization (WHO) guidance on eliminating TT at the programme level
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As trachomatous trichiasis (TT) becomes rarer, obtaining precise estimates of its prevalence becomes progressively more difficult.
The prevalence of TT is measured at the district level, the administrative unit for healthcare management. Districts have a population of between 100 000 – 250 000 people and are referred to as evaluation units (EU). The elimination prevalence threshold for TT is set at < 0.2% in people aged over 15 years in each formerly-endemic EU.
For programmatic surveys specifically designed to measure the prevalence of TT unknown to the health system at the EU level, the current WHO recommendation is that enough households are visited to examine 2 818 individuals aged 15 years and above. This number should provide sufficient data (power) to enable an accurate estimation of the prevalence of trachomatous trichiasis (TT).
As an example, here are some typical figures from a programmatic survey of TT in an evaluation unit (EU):
- Number of people aged 15 years and above = 100,000.
- Prevalence of TT unknown to the health system = 0.5% in people aged 15 years and above.
- Target for elimination: prevalence of TT unknown to the health system < 0.2% in people aged 15 years and above.
- Estimated number of TT cases that need treatment = 100,000 x 0.5% = 500.
- The TT programme must set a target to achieve a prevalence < 0.2% in people aged 15 years and above at the end of a specified time period, e.g., in 3 years.
It is important to remember that the number of prevalent cases is just an estimate to help programmes to plan for service provision and resource allocation. Programmes should aim to cover each entire EU with case finding and TT management as this may identify more, or fewer, people with TT than the estimate has indicated.
National programmes can use one of three methods to assess whether the elimination prevalence target for trachomatous trichiasis has been reached within a country:
- A population-based prevalence survey powered at the level of the evaluation-unit (i.e. a population of 100 000 – 250 000 people), or
- House-to-house case searches, which can be integrated with other public health activities, or
- A combination of data from multiple adjacent evaluation units. Professional statistical advice to identify the best way to achieve this, is being generated: more advice from WHO will follow soon.
As you watch the video, consider how data can be used to motivate a district team to maintain implementation of SAFE and scale up services.
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