Ruling out early trimester pregnancy when implementing community-based deworming programs

Background: Large-scale deworming programs have, to date, mostly targeted preschool- and school-age children. As community-based deworming programs become more common, deworming will be offered to women of reproductive age. The World Health Organization recommends preventive chemotherapy be administered to pregnant women only after the first trimester. It is therefore important for deworming programs to be able to identify women in early pregnancy. Our objective was to validate a short questionnaire which could be used by deworming program managers to identify and screen out women in early pregnancy. Methodology/Principal findings: In May and June 2018, interviewers administered a questionnaire, followed by a pregnancy test, to 1,203 adult women living in the Peruvian Amazon. Regression analyses were performed to identify questions with high predictive properties (using the pregnancy test as the gold standard). Test parameters were computed at different decision tree nodes (where nodes represented questions). With 106 women confirmed to be pregnant, the positive predictive value of asking the single question ‘Are you pregnant?’ was 100%, at a ‘cost’ of a false negative rate of 1.9% (i.e. 21 women were incorrectly identified as not pregnant when they were truly pregnant). Additional questions reduced the false negative rate, but increased the false positive rate. Rates were dependent on both the combination and the order of questions. Conclusions/Significance: To identify women in early pregnancy when deworming programs are community-based, both the number and order of questions are important. The local context and cultural acceptability of different questions should inform this decision. When numbers are manageable and resources are available, pregnancy tests can be considered at different decision tree nodes to confirm pregnancy status. Trade-offs in terms of efficiency and misclassification rates will need to be considered to optimize deworming coverage in women of reproductive age. Author summary: To date, large-scale deworming programs have strategically targeted the high risk groups of school-age and preschool-age children in worm-endemic areas using the highly cost-effective existing infrastructure of schools. To achieve elimination of worm-attributable morbidity, however, adult populations will also need to be treated. The World Health Organization considers women of reproductive age to also be a high risk group for worm-attributable morbidity and they will be increasingly included in large-scale community-based deworming programs. Although deworming treatment is considered safe and effective at any time, it is recommended that pregnant women in the first trimester be excluded from deworming treatment. Therefore, program managers need to have a screening tool in order to rule out early trimester pregnant women during deworming program implementation. To respond to this need, we evaluated the predictive properties of a parsimonious set of questions in a study population of adult women of reproductive age in a worm-endemic region of the Peruvian Amazon. We present several question scenarios to assist program managers in using questions to rule out early trimester pregnant women. Adapted to local cultural settings, such a screening tool can optimize deworming coverage in women of reproductive age.