How to monitor and evaluate trachoma programmes
Deciding whether to start SAFE interventions
Baseline surveys must be undertaken before any SAFE interventions are started. Population based surveys are commended using WHO methods.
The key indicators which guide the decision on beginning SAFE interventions are:
Prevalence of trachomatous inflammation-follicular (TF) ≥ 5% in children aged 1-9 years
Prevalence of trachomatous trichiasis (TT) ≥ 0.2% in people aged 15 years and above
Detailed guidance on how to plan the implementation of SAFE is given in the Trachoma Action Planning guide
Evaluation of SAFE interventions
The key indicators which determine whether trachoma is a public health problem are prevalence of TF of ≥ 5% in children aged 1-9 and prevalence of TT of ≥ 0.2% in people aged 15+ years.
Trachoma surveys are undertaken by the country programs using Tropical Data.
Impact surveys and pre-validation surveillance surveys are based on the TF prevalence, although data on trichiasis are also collected.
Impact surveys are conducted six to 12 months after the final planned round of mass drug administration (MDA). They are carried out to determine:
if interventions have achieved the elimination threshold (TF of <5% in children aged 1-9 years) or
if further AFE interventions are needed.
Population-based impact surveys are carried out 6-12 months after the final planned MDA round to assess the prevalences of TF and TT. Surveys are recommended as follows:
after 1 MDA annual round if baseline TF prevalence = 5-9.9%
after 3 years of MDA if baseline TF prevalence = 10-29.9%
after 5 years of MDA if baseline TF prevalence ≥ 30%
Once the impact indicator for TF has reached the elimination target, MDA is stopped. TT surgery would continue to manage all remaining TT cases and new cases. F&E interventions should also be continued.
When the impact indicator for TT has reached the elimination target, the programme can transition from detecting and managing in an active manner, to providing services for trichiasis surgery as part of routine eye care.
Surveillance surveys use ongoing data collection and methods interpretation which guides key decisions. These surveys can be:
- Pre-validation surveillance surveys
- Post-validation surveillance surveys
Pre-validation surveillance surveys for trachoma are carried out at least 24 months after the last impact survey has shown a TF prevalence less than 5% in children aged 1-9. These surveys are done to verify that reductions in TF prevalence have been sustained.
Trachoma surveillance is the monitoring and evaluation activities which are carried out to assess the outcome of a trachoma elimination programme. Pre-validation surveillance surveys begin after elimination prevalence targets have been achieved in a defined trachoma endemic area and A interventions have been stopped.
If a surveillance survey shows that the elimination target for TF has been maintained, and data from any of the WHO-recommended methods for TT prevalence estimation have demonstrated that TT prevalence is <0.2% in adults aged 15 years and above, then trachoma can be considered to have been eliminated as a public health problem from the district. The remaining cases of TT surgeries are then provided as part of eye care services and not a dedicated TT programme.
When all endemic districts have achieved elimination, the country is eligible for being validated as having eliminated trachoma as a public health problem.
Post-validation surveillance surveys are undertaken following validation of elimination of trachoma as a public health problem. This further routine surveillance is needed to monitor if elimination is being sustained. A number of approaches have been used in trachoma endemic countries for routine post-validation surveillance, including:
- Sentinel surveillance for active trachoma in communities (Ghana)
- Routine surveillance for trachoma through health facilities and schools (Oman)
- Active case search for trichiasis in the community (Ghana and Morocco).
Recently, research on the use of antibody-based multiplex assays has showed promising results as an additional tool for evaluating the transmission of trachoma. An alternative indicator to clinical signs for detecting ongoing infection within a community may be useful where elimination of trachoma as a public health problem has been achieved.
Ghana became the first Sub Saharan country to be validated for Elimination of Trachoma. This paper shares some insights into the process of surveillance that was undertaken:
Operational adaptations of the trachoma pre-validation surveillance strategy employed in Ghana: a qualitative assessment of successes and challenges.
© London School of Hygiene & Tropical Medicine/ENVISION, RTI CC BY-NC-SA