The Global Trachoma Mapping Project: Methodology of a 34-Country Population-Based Study

Abstract

Purpose: To complete the baseline trachoma map worldwide by conducting population-based surveys in an estimated 1238 suspected endemic districts of 34 countries.

Methods: A series of national and sub-national projects owned, managed and staffed by ministries of health, conduct house-to-house cluster random sample surveys in evaluation units, which generally correspond to "health district" size: populations of 100,000-250,000 people. In each evaluation unit, we invite all residents aged 1 year and older from h households in each of c clusters to be examined for clinical signs of trachoma, where h is the number of households that can be seen by 1 team in 1 day, and the product h × c is calculated to facilitate recruitment of 1019 children aged 1-9 years. In addition to individual-level demographic and clinical data, household-level water, sanitation and hygiene data are entered into the purpose-built LINKS application on Android smartphones, transmitted to the Cloud, and cleaned, analyzed and ministry-of-health-approved via a secure web-based portal. The main outcome measures are the evaluation unit-level prevalence of follicular trachoma in children aged 1-9 years, prevalence of trachomatous trichiasis in adults aged 15 + years, percentage of households using safe methods for disposal of human feces, and percentage of households with proximate access to water for personal hygiene purposes.

Results: In the first year of fieldwork, 347 field teams commenced work in 21 projects in 7 countries.

Conclusion: With an approach that is innovative in design and scale, we aim to complete baseline mapping of trachoma throughout the world in 2015.

Keywords: Blindness; mHealth; prevalence study; trachoma; trichiasis.

FIGURE 1.

Scale of the Global Trachoma Mapping Project.

FIGURE 2.

Selection criteria for Global Trachoma Mapping Project (GTMP) field team trainees.

FIGURE 3.

Global Trachoma Mapping Project (GTMP) data handling and flow. (1) The field team upload the raw data, which are available for review and download by designated ministry of health (MOH) personnel. (2) The GTMP Data Manager cleans the raw data by checking for and querying (with the field team) any errors, internal inconsistencies or missing data. (3) A designated MOH official evaluates the cleaned dataset, and then either approves it (“approval C”) or queries it; once approved, analyses to generate evaluation unit-level prevalences are run automatically. (4) A designated MOH official evaluates the prevalence figures and either approves them (“approval P”) or queries them. (5) Once approved, categorical prevalence data are uploaded to the Global Atlas of Trachoma (GAT).