Trachoma survey methods: a literature review

Area of Science:

• Ophthalmology
• Public Health
• Epidemiology

Background:

• Reliable population-based prevalence data are crucial for effective trachoma control programs.
• Data are lacking for 22 of 56 endemic countries, hindering planning and evaluation.
• Three survey methods exist: cluster random sampling (CRS), trachoma rapid assessment (TRA), and acceptance sampling trachoma rapid assessment (ASTRA).

Purpose of the Study:

• To review and compare the effectiveness of different trachoma survey methods.
• To identify the most suitable method for population-based prevalence estimation.
• To highlight areas for methodological improvement in trachoma surveys.

Main Methods:

• Review of advocated survey methods for trachoma: CRS, TRA, and ASTRA.
• Analysis of the benefits and limitations of each method regarding sampling, prevalence estimation, accuracy, and consistency.
• Evaluation of methodological deficiencies in existing CRS surveys.

Main Results:

• Cluster random sampling (CRS) is simple, efficient, repeatable, and provides population-based prevalence estimates.
• Trachoma rapid assessment (TRA) has limitations including non-representative sampling and lack of accuracy.
• Acceptance sampling trachoma rapid assessment (ASTRA) is complex and may yield imprecise estimates, especially for cicatricial signs.

Conclusions:

• Cluster random sampling (CRS) remains the 'gold' standard for trachoma surveys.
• Methodological improvements are needed in CRS, including sample-size calculations and grader standardization.
• Harmonization of survey methods and continued use of CRS are advocated for global elimination of blinding trachoma.