*2.4. Statistical Analysis*

The prevalence of human infection was estimated by the formula: (1) Observed prevalence (%) = No. of egg-positive/No. of examined people × 100% (by using Kato-Katz method). (2) Observed prevalence (%) = (No. of blood-positive/No. of examined people × 100% (by using IHA test). (3) Observed prevalence (%) = (No. blood-positive/No. of examined people by using IHA test) × (No. of egg-positive/No. of examined people by using Kato-Katz method) × 100% (by using Kato-Katz and IHA).

The adjusted prevalence is the observed prevalence of human infection after taking the sensitivity and specificity of the Kato-Katz method into consideration. The adjusted formula: *p*' = *P*0+β−1 *<sup>α</sup>*+β−1 *p*': adjusted prevalence, *p0*: observed prevalence, α: sensitivity, β: specificity [10].

Two stool samples with three thick smears each are used as the diagnostic gold standard [11]. The sensitivities of two smears and three smears Kato-Katz methods are 64% and 75% separately. The specificities are 100% for both of them; the sensitivity and specificity of IHA and the observed prevalence measured by it are not satisfy the condition of adjusted formula [10], therefore, the results of IHA cannot be adjusted.

All data were entered and built a database with Microsoft Excel, and statistical analyses were performed with the use of SPSS (version25, IBM, New York, NY, USA) and SAS software (University Edition, The Statistical Analysis System, Raleigh, NC, USA). We used the chi-square test, including testing for trend when appropriate, to examine any difference and change over time. Two-sided *p* values were calculated for all comparisons [12–14].


