Are studies underestimating the effects of sanitation on child nutrition? – Authors' reply
Authors: Amy J Pickering, Maria Laura Alzua
Journal: The Lancet Global Health (2016)

Should child growth replace diarrhoea as the primary child health outcome for sanitation trials? We appreciate Derek Headey's comment in relation to our trial1Pickering AJ Djebbari H Lopez C Coulibaly M Alzua ML Effect of a community-led sanitation intervention on child diarrhoea and child growth in rural Mali: a cluster-randomised controlled trial.Lancet Glob Health. 2015; 3: e701-e711Summary Full Text Full Text PDF Scopus (220) Google Scholar that the window of opportunity to plausibly affect growth faltering is from in utero up to 24 months, and therefore that sanitation trials should focus growth assessments in children with exposure to the intervention who are younger than 24 months. Ongoing sanitation trials in rural Kenya (NCT01704105), Bangladesh (NCT01590095), and Zimbabwe (NCT01824940) have chosen to enrol target children in utero precisely because of the recognition that child stunting and environmental enteric dysfunction can begin before birth.2Arnold BF Null C Luby SP et al.Cluster-randomised controlled trials of individual and combined water, sanitation, hygiene and nutritional interventions in rural Bangladesh and Kenya: the WASH Benefits study design and rationale.BMJ Open. 2013; 3 (e003476): e003476Crossref Scopus (147) Google Scholar However, the effect of enteric pathogen exposure—either through reduced acute diarrhoea or asymptomatic infections3Mbuya MN Humphrey JH Preventing environmental enteric dysfunction through improved water, sanitation and hygiene: an opportunity for stunting reduction in developing countries.Matern Child Nutr. 2015; (published online Nov 6.)https://doi.org/10.1111/mcn.12220Crossref Scopus (116) Google Scholar—is likely to be one of many causes of linear growth faltering. In some settings, competing risks such as poor nutrition and non-enteric infections (eg, malaria) could overshadow improved sanitation's contribution to growth. Child growth is also unable to capture potential health benefits of sanitation interventions for children older than 2 years. For these reasons, it could be premature to rely exclusively on anthropometry measurement before additional sanitation intervention trials successfully show an effect on child growth. Although we agree with Headey that caregiver-reported diarrhoea can be a biased outcome, we see value in measuring the effect of sanitation interventions on more objective indicators of enteric infections. Notably, recently developed molecular techniques allow for the simultaneous detection of many relevant diarrhoeal pathogens in stool samples, including bacteria, viruses, protozoans, and soil-transmitted helminths.4Liu J Gratz J Amour C et al.A laboratory-developed TaqMan array card for simultaneous detection of 19 enteropathogens.J Clin Microbiol. 2013; 51: 472-480Crossref PubMed Scopus (257) Google Scholar Antibody measures of infection in saliva, blood, and stools provide additional multiplex opportunities to objectively measure enteric pathogens.5Griffin SM Chen IM Fout GS Wade TJ Egorov AI Development of a multiplex microsphere immunoassay for the quantitation of salivary antibody responses to selected waterborne pathogens.J Immunol Methods. 2011; 364: 83-93Crossref PubMed Scopus (39) Google Scholar, 6Moss DM Priest JW Hamlin K et al.Longitudinal evaluation of enteric protozoa in haitian children by stool exam and multiplex serologic assay.Am J Trop Med Hyg. 2014; 90: 653-660Crossref PubMed Scopus (34) Google Scholar Continued advancements in molecular techniques are reducing costs and increasing the feasibility of their use in low-income settings. Although the high incidence of asymptomatic infections precludes the use of pathogen presence as a direct indicator for clinical diarrhoea,7Kotloff KL Nataro JP Blackwelder WC et al.Burden and aetiology of diarrhoeal disease in infants and young children in developing countries (the Global Enteric Multicenter Study, GEMS): a prospective, case-control study.Lancet. 2013; 382: 209-222Summary Full Text Full Text PDF PubMed Scopus (2261) Google Scholar enteric pathogen infection status would be a valuable outcome to understand the ability of sanitation interventions to interrupt transmission of diarrhoeal pathogens. We propose that enteric pathogen detection be deemed a complementary outcome to child growth for a more comprehensive understanding of the potential benefits of sanitation trials. We declare no competing interests. Are studies underestimating the effects of sanitation on child nutrition?As other researchers have done, Amy Pickering and colleagues (November, 2015)1 focused on short-recall diarrhoea incidence as the main outcome in their randomised trial of the effects of a community-led sanitation intervention in Mali. As Pickering and colleagues1 noted, this indicator has well known flaws associated not only with seasonality, but also with potential reporting bias and other measurement errors. These flaws raise the possibility of crucial type II errors that justify a serious reappraisal of the long-standing practice of using this indicator as the primary means to evaluate sanitation interventions. Full-Text PDF Open Access