Tropical Data: Approach and Methodology as Applied to Trachoma Prevalence Surveys

Figures & data

Figure 1. Decision-making for baseline, impact and surveillance surveys and SAFE (surgery, antibiotics, facial cleanliness and environmental improvement) interventions for trachoma elimination.^8,9

Note: TF: trachomatous inflammation—follicular; TT: trachomatous trichiasis

Figure 2. Tropical Data organisation chart for supporting trachoma surveys.

ITI: International Trachoma Initiative; LSHTM: London School of Hygiene & Tropical Medicine; WHO: World Health Organization; WASH: Water, Sanitation and Hygiene.

Figure 3. Tropical Data quality and standardisation process.

Table 1. Inputs to calculate sample size for baseline, impact, surveillance and TT-only surveys.^{13, 28}

	Input
Variable	Baseline^Citation28	Baseline (with expectation of low TF prevalence), impact, and surveillance^Citation28	TT-only^Citation13
Expected prevalence (%)^a	10	4	0.2
Design effect^Citation31	3.69	2.63	1.47
Standard deviation for 95% confidence interval	1.96	1.96	1.96
Absolute precision (%)	3	2	0.2
Number to examine	1418	970	2818
Non-response rate inflation factor^b	1.2	1.2	1.2
Targeted number to enumerate^c	1701	1164	3382

TF: trachomatous inflammation—follicular; TT: trachomatous trichiasis.

^aFor baseline, impact, and surveillance surveys, this is the expected trachomatous inflammation—follicular prevalence in 1–9-year-olds. For TT-only surveys, this is the expected TT prevalence in ≥ 15-year-olds.

^bAn arbitrary inflation factor of 1.2 is used unless previous work enables the use of an actual non-response rate for the particular population and setting.

^cFor baseline, impact, and surveillance surveys, this is the number of children aged 1–9 years to enumerate. For TT-only surveys, this is the number of adults aged ≥15 years to enumerate.

Figure 4. Tropical Data trachoma training cascade.

Figure 5. Roles and responsibilities during the Tropical Data survey process.

EUID: Evaluation Unit Identification number; WHO: World Health Organization.

Solomon AW, Zondervan M, Kuper H, Buchan JC, Mabey DCW, Foster A. Trachoma Control: A Guide for Programme Managers. Geneva: World Health Organization; 2006.

 Google Scholar

World Health Organization. Report of the 3rd global scientific meeting on trachoma, Johns Hopkins University, Baltimore, MA, 19-20 July 2010 (WHO/PBD/2.10). 2010.

 Google Scholar

World Health Organization. Design and validation of a trachomatous trichiasis-only survey: strategic and technical advisory group for neglected tropical diseases, working group on monitoring and evaluation. Geneva: World Health Organization; 2017. License: CC BY-NC-SA 3.0 IGO. https://apps.who.int/iris/handle/10665/259815.

 Google Scholar

World Health Organization. Design parameters for population-based trachoma prevalence surveys. Geneva: World Health Organization; 2018. Licence: CC BY-NC-SA 3.0 IGO. https://www.who.int/publications/i/item/who-htm-ntd-pct-2018.07.

 Google Scholar

Macleod CK, Bailey RL, Dejene M, et al. Estimating the intracluster correlation coefficient for the clinical sign “trachomatous inflammation—follicular” in population-based trachoma prevalence surveys: results from a meta-regression analysis of 261 standardized preintervention surveys carried out in Ethiopia, Mozambique, and Nigeria. Am J Epidemiol. 2020;189(1):68–76. doi:10.1093/aje/kwz196.

 PubMed Web of Science ®Google Scholar