{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,26]],"date-time":"2026-08-26T18:19:03Z","timestamp":1787768343538,"version":"build-2784847793"},"reference-count":48,"publisher":"Public Library of Science (PLoS)","issue":"8","license":[{"start":{"date-parts":[[2026,8,26]],"date-time":"2026-08-26T00:00:00Z","timestamp":1787702400000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100000009","name":"Foundation for the National Institutes of Health","doi-asserted-by":"publisher","award":["K23HL173694"],"award-info":[{"award-number":["K23HL173694"]}],"id":[{"id":"10.13039\/100000009","id-type":"DOI","asserted-by":"publisher"}]},{"name":"Universidad Nacional del Altiplano"}],"content-domain":{"domain":["www.plosone.org"],"crossmark-restriction":false},"short-container-title":["PLoS One"],"abstract":"<jats:sec id=\"sec001\">\n                    <jats:title>Background<\/jats:title>\n                    <jats:p>In Peru, legally mandated universal micronutrient supplementation policies preclude randomized trials.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec id=\"sec002\">\n                    <jats:title>Objective<\/jats:title>\n                    <jats:p>To evaluate hemoglobin (Hb) outcomes associated with enhanced follow-up of therapeutic iron or preventive multiple micronutrient powder (MNP) supplementation among high-altitude infants within a real-world natural experiment.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec id=\"sec003\">\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>This observational study leveraged a policy-driven natural experiment to analyze two population-based cohorts of 317 infants aged 6\u201312 months from Puno, Peru (3,832 m), evaluated before and after implementation of strict follow-up. According to national guidelines, infants with anemia received therapeutic iron syrup (ferrous sulfate or iron polymaltose), while non-anemic infants received preventive MNP. Supplements were provided monthly for six months. Hemoglobin was measured at baseline and follow-up and adjusted for altitude using the WHO 2024 criteria. Adequate Hb response was defined as an increase \u22651 g\/dL. Multivariable regression models assessed factors associated with hemoglobin response.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec id=\"sec004\">\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>Overall, 14.8% of infants achieved an Hb increase \u22651 g\/dL (18.7% vs. 11.8% in the strict and non-strict follow-up groups, respectively). Among non-anemic infants at baseline, adequate Hb response was more frequent under strict follow-up (8.3% vs. 2.7%). In the prespecified primary adjusted model, strict follow-up was associated with higher odds of achieving an adequate Hb response (aOR 3.53; 95% CI 1.40\u20138.84), compared with the crude estimate (OR 2.45; 95% CI 1.30\u20134.63). In sensitivity analyses incorporating additional socioeconomic, nutritional, and program-related covariates, the association was attenuated (aOR 2.18; 95% CI 0.53\u20138.99). When evaluated as a continuous outcome, strict follow-up was associated with greater hemoglobin increases (adjusted mean difference 0.74 g\/dL; 95% CI 0.23\u20131.25). At six months, altitude-adjusted anemia prevalence was lower in the strict follow-up group than in the non-strict group (25.2% vs. 38.2%, p\u2009=\u20090.019). Baseline anemia and older age were independently associated with larger hemoglobin gains.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec id=\"sec005\">\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>Strict follow-up was associated with greater increases in hemoglobin concentration and lower altitude-adjusted anemia prevalence at follow-up. Although anemia prevalence was lower among infants receiving strict follow-up, residual anemia remained common after six months of supplementation. These findings suggest that enhanced programmatic follow-up may improve hematologic outcomes under routine public health conditions, while additional factors contributing to anemia persistence warrant further investigation.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1371\/journal.pone.0356793","type":"journal-article","created":{"date-parts":[[2026,8,26]],"date-time":"2026-08-26T17:31:36Z","timestamp":1787765496000},"page":"e0356793","update-policy":"https:\/\/doi.org\/10.1371\/journal.pone.corrections_policy","source":"Crossref","is-referenced-by-count":0,"title":["Hemoglobin outcomes associated with supervised therapeutic iron or preventive multiple micronutrient powder supplementation in high-altitude Peruvian infants: A real-world natural experiment"],"prefix":"10.1371","volume":"21","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-3326-0437","authenticated-orcid":true,"given":"Cinthya","family":"V\u00e1squez-Vel\u00e1squez","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0350-3469","authenticated-orcid":true,"given":"Parminder S.","family":"Suchdev","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Chris A.","family":"Rees","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9638-0076","authenticated-orcid":true,"given":"Yury R.","family":"Quispe-Lipa","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6826-5561","authenticated-orcid":true,"given":"Lidia S.","family":"Caballero","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Gustavo F.","family":"Gonzales","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"340","published-online":{"date-parts":[[2026,8,26]]},"reference":[{"key":"pone.0356793.ref001","unstructured":"World Health Organization. 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