Prevalence of Trachoma in Gambella Region, Ethiopia: Results of Three Population-Based Prevalence Surveys Conducted with the Global Trachoma Mapping Project.

PURPOSE: In Ethiopia, trachoma is a major public health problem, accounting for 11.5% of all cases of blindness. In Gambella, one of the country's most remote regions, the 2005-2006 National Survey of Blindness, Low Vision and Trachoma estimated a region-level prevalence of active trachoma of 19.1% in those aged 1-9 years. Detailed district or sub-regional level estimates are required to implement interventions. METHODS: Population-based prevalence surveys were carried out following a 2-stage cluster random sampling methodology and Global Trachoma Mapping Project protocols. As the 13 districts (woredas) in Gambella had relatively small populations, they were grouped together to form three evaluation units (EUs) of about 100,000 persons each, and all subsequent survey planning and sampling was carried out at EU-level. RESULTS: Altogether, 558 cases of TF (17.2%) were identified in 3238 children aged 1-9 years across the three EUs. The adjusted TF prevalences in 1-9-year-olds for the three EUs were 11.5%, 12.5% and 19.3%; 14.4% for Gambella overall. A total of 142 cases of trichiasis (3.8%) were identified among 3781 adults aged 15 years or older, with age- and sex-adjusted EU-level trichiasis prevalences in adults being 0.8%, 1.3% and 2.4%; 1.5% overall. CONCLUSION: The high prevalences of TF and trichiasis throughout Gambella indicate a need for rapid scaling up of the World Health Organization SAFE strategy (surgery, antibiotics, facial cleanliness, and environmental improvement) to help meet the 2020 target of global elimination of trachoma as a public health problem

Optimising age adjustment of trichiasis prevalence estimates using data from 162 standardised surveys from seven regions of Ethiopia.

PURPOSE: The prevalence of trichiasis is higher in females and increases markedly with age. Surveys carried out in the daytime, particularly in developing countries, are prone to find older individuals and females at home at the time of the survey. Population-level trichiasis estimates should adjust sample proportions to reflect the demographic breakdown of the population, although the most accurate method of doing this is unclear. METHODS: Having obtained data from 162 surveys carried out in Ethiopia as part of the Global Trachoma Mapping Project from 2012 to 2015, we used internal validation with both Brier and Logarithmic forecast scoring to test stratification models to identify those models with the highest predictive accuracy. Selection of partitions was undertaken by both simple random sampling (SRS) and cluster sampling (CS) over 8192 selections. RESULTS: A total of 4529 (1.9%) cases of trichiasis were identified from 241,139 individuals aged ≥15 years from a total of 4210 kebeles and 122,090 households visited. Overall, the binning method using 5-year bands from age 15 to 69 years, with coarser binning in 20-year age-bands above this age, provided the best predictive accuracy, in both SRS and CS methodologies and for both the Brier and Logarithmic scoring rules. CONCLUSION: The greatest predictive accuracy for trichiasis estimates was found by adjusting for sex and in 5-year age-bands from the age of 15 to 69 years and in 20-year age-bands in those aged 70 years and greater. Trichiasis surveys attempting to make population-level inferences should use this method to optimise surgery backlog estimates