The "F" in SAFE: Reliability of assessing clean faces for trachoma control in the field

Background: Although facial cleanliness is part of the SAFE strategy for trachoma there is controversy over the reliability of measuring a clean face. A child’s face with no ocular and nasal discharge is clean and the endpoint of interest, regardless of the number of times it must be washed to achieve that endpoint. The issue of reliability rests on the reproducibility of graders to assess a clean face. We report the reproducibility of assessing a clean face in a field trial in Kongwa, Tanzania. Methods/Findings: Seven graders were trained to assess the presence and absence of nasal and ocular discharge on children’s faces. Sixty children ages 1–7 years were recruited from a community and evaluated independently by seven graders, once and again about 50 minutes later. Intra-and inter-observer variation was calculated using unweighted kappa statistics. The average intra-observer agreement was kappa = 0.72, and the average inter-observer agreement was kappa = 0.78. Conclusions: Intra-observer and inter-observer agreement was substantial for the assessment of clean faces using trained Tanzania staff who represent a variety of educational backgrounds. As long as training is provided, the estimate of clean faces in children should be reliable, and reflect the effort of families to keep ocular and nasal discharge off the faces. These data suggest assessment of clean faces could be added to trachoma surveys, which already measure environmental improvements, in districts. Author summary: The repeated infection that causes trachoma is spread from person to person via infected ocular and nasal secretions. The World Health Organization (WHO) strategy for trachoma control includes keeping children’s faces clean of discharges, yet “clean faces” are not measured in most of the district surveys that evaluate the impact of programs. We studied the reliability of assessing “clean faces” in 60 children in a village in Tanzania, using trained Tanzania staff with a variety of educational backgrounds. When assessing the same child twice after 50 minutes, the staff showed substantial agreement with themselves. The agreement between a senior grader and each staff member was also excellent. The data suggest that clean faces in children can be reliably assessed, and should be added to district surveys that are measuring the impact of programs on control of trachoma.