Evaluating Precision of a Trachomatous Trichiasis (TT) Super Survey with Modulating Sample Sizes in Tanzania

ABSTRACT

As trachoma programs move towards eliminating trachoma as a public health problem, the number of surveys necessary to evaluate the status of trachomatous trichiasis (TT) increases. Currently, the World Health Organization endorses a district-level population-based prevalence survey for trachoma that involves a two-stage cluster design. We explored the validity of implementing this survey design in larger geographic areas to gain cost efficiencies. We evaluated the change in precision due to combining geographically contiguous and homogenous districts into single evaluation units (EUs) and modulating the sample size by running simulations on existing datasets. Preliminary findings from two opportunities in Tanzania show variability in the appropriateness in conducting this survey across larger geographies. These preliminary findings stress the importance of determining what is meant by homogeneity in terms of TT before combining multiple districts into a single EU.

KEYWORDS:

• Trachoma
• Trachomatous Trichiasis
• Survey
• Sample Size
• Cluster Design

Disclosure Statement

Authors have no conflict of interest.

Financial support

The TT-only surveys discussed in this paper were funded by the Queen Elizabeth Diamond Jubilee Trust Trachoma Initiative through Sightsavers and Helen Keller International. This analysis was made possible thanks to funding from ENVISION, a global project led by RTI International in partnership with CBM International, The Carter Center, Fred Hollows Foundation, Helen Keller International, IMA World Health, Light for the World, Sightsavers, and World Vision. ENVISION was funded by the United States Agency for International Development under cooperative agreement No. AID-OAA-A-11-00048. The period of performance for ENVISION was September 30, 2011 through September 30, 2019. For more information, go to www.NTDenvision.org.

The authors alone are responsible for the views expressed in this article, which do not necessarily represent the views, decisions, or policies of the institutions with which the authors are affiliated, the United States Agency for International Development, or the United States Government.

Additional information

Funding

This work was supported by the US Agency for International Development (USAID) and the ENVISION project led by RTI International under cooperative agreement No. AID-OAA-A-11-00048.