Study design, period and setting
A community-based cross-sectional study design was used. Fieldwork was undertaken from March 11, 2017 to April 26, 2107. The estimated population of Wadla district was 128,170 with 64,574 males and 63,596 females. There were 28,414 households in this district with an average of 4.5 persons per house. The district had 1 general hospital, 7 health centers, and 20 health posts.
The sampling frame was children aged 1 to 5 years old in 150 rural villages of Wadla district. The study units were heads from the selected rural households that also had preschool children.
Sample size determination
We estimated the required sample size using the single population proportion formula. We assumed, based on previous surveys, an observed prevalence of active trachoma (12.1%) (14), which we wished to estimate with 95% confidence within ±5%. We used a design effect of 1.5, and allowed for 10% non- response rate. Through multiplying the sample size by the design effect, 1.5 and incorporating a 10% non-response rate, we estimated 273 children that were needed to be framed in selected households.
A multistage cluster sampling technique was applied. Wadla district had 20 kebeles (sub-districts) that comprise 247 villages. Twelve of the kebeles were rural, whereas eight of the kebeles were urban. Regarding the villages, 150 of the 247 villages were rural. We used simple random sampling to select 30 of the 150 rural villages. There were 967 households in the selected 30 villages, but only 499 of those households had preschool children. Thus, those 499 households were visited. Heads of households were interviewed for socio-demographic and economic information, plus housing and environmental conditions, and all children aged between 1 and 5 years who had been resident in the district for at least six months were invited to be examined. Eye examiners used the WHO simplified trachoma grading scheme to grade signs of trachoma (15) (Figure1).
The sample size calculated was 273 using single population proportion formula, but as the sampling procedure was cluster sampling, the numbers of screened children were 596 from all 30 villages.
Clean face: A face of child that was free of eye discharges, nose discharges or flies at the time of eye examination
Preschool: Children whose age were greater than and equal to 1 year and less than or equal to 5 years old.
Village: A grouping of homes that contained at least 30 households organized as one peasant association
Fly in a home: When there is/are a countable fly in a house during data collection, despite the number of flies
Active trachoma: The presence of at least one of the two signs of active trachoma according to the WHO simplified trachoma grading scheme (TF or TI) in at least one eye (16).
Trachomatis inflammation—follicular (TF): The presence of five or more follicles each having a diameter of at least 0.5mm in the central part of the upper tarsal conjunctiva (16).
Trachomatis inflammation—intense (TI): A pronounced inflammatory thickening of the upper tarsal conjunctiva that obscures more than half of the normal deep tarsal blood vessels (16).
Trachomatis scarring (TS): The presence of easily visible scarring in the upper tarsal conjunctiva (16)
Trachomatis trichiasis (TT): The presence of at least one eyelash rubs on the eyeball or evidence of removal of in-turned eyelashes in the two weeks before examination (16).
Corneal opacity (CO): the presence of easily visible corneal opacity over the pupil (16)
Exclusion and inclusion criteria
All the children belong to the appropriate age range mentioned above and who had lived in the district for at least 6 months, who were resident in selected villages and available at the time of study were invited to be included. Children who were seriously ill or for whom informed consent was not given by parents or guardians were excluded.
The outcome variable was active trachoma and measured by physical examination. A number of dependent variables were considered that includes socio-demographic, environmental, hygiene and sanitation, and children’s demographic data.
Data collection tools and procedures
In collecting the data, face to face interviews, observation using a checklist and clinical eye examination were used. Experienced health informatics professionals were using structured interview questions that prepared from pieces of literature (17, 18), while they collected the data on a socio-demographic status, environmental, and housing conditions. All the questionnaires of socio-demographic status, housing, and environmental condition, observation checklist, and eye examination tools were pretested and validated before data collection in Kosomender, Meket district, a district bordering Wadla to the north. A household wealth index was developed using composite indicators for rural residents’ assets: livestock ownership, size of agricultural land and quantity of crop production.
Two integrated eye care workers performed the eye examination. Those integrated eye care workers are ophthalmic nurses who had been previously trained for a total duration of one month for the purposes of contributing to the 2013–2014 national trachoma survey. The Carter Center delivered that previous training using both pictures and live patients as media of instruction. However, for the purpose of this study, the trachoma graders undertook refreshment training for 5 days. This training considers examination of 58 live patients and 100 pictures of different trachoma signs. Trainers, whose grades were used as the gold-standard assessment assessed graders. The training was also delivered for interviewers. Interviewers assisted graders by recording clinical grades, and data related to each household's socio-demographic status and environmental situation. The trainers emphasized on the objectives, procedures of data collection and mode of communication between graders and interviewers. When undertaking the fieldwork, graders initially observed the eyelashes and cornea of study subjects, looking for TT and CO, then everted the upper lid and inspected the upper tarsal conjunctiva for TF, TI, or TS. Binocular lenses (×2.5) and penlight torches were used (4) to magnify the examined eye.
Data analysis and presentation
The data were checked for completeness, coded and entered into Epi-info version 7, and transferred to SPSS version 23 for analysis. The data were checked for normality using Hosmer-Lemeshow-goodness-of-fit. A univariate analysis model were carried out, and variables that had a p-value of <0.25 in a binary logistic regression model were included to the multivariate logistic regression analysis. Potential co-linearity was also considered and tested using multi co-linearity model in considering tolerance and variance inflection factor (VIF). Variables with a p-value of <0.05 in the multivariate logistic regression analysis were considered as statistically significant. A principal component analysis was performed to categorize households’ wealth into poorer, poorest, middle, richer, and richest. However, for the presentation of the variables, the wealth index was grouped into three; lowest, middle, and highest. The procedure of eye examination and result reporting presented in figure2. Both active trachoma and cicatricial trachoma were modeled as outcome variables. Thus, children were screened for both Active and cicatricial types of trachoma (Figure2).
Data quality assurance
The questionnaire was prepared in English and translated to Amharic, then re-translated to English (to check for accuracy) by individuals, who are fluent in both English and Amharic. Both graders and one of the researchers, principal investigator had been participated in a community-based trachoma survey and training before starting the present study. The interviewers had also previous experience in a community-based data collection.