{
  "abstract": "Genetic ancestry composition has been used extensively as a predictor of clinical outcomes, multiomic biomarkers, and endophenotypes, but the models have most often used untransformed ancestry fractions as explanatory variables. Under a simplex constraint results from this type of model can be uninterpretable and misleading. We demonstrate the use of multiple transformed log ratio coordinates of ancestral proportions as predictors in a study of excreted myeloperoxidase (MPO), a neutrophilic enzyme used as a fecal biomarker to measure intestinal inflammation and enteropathy. We show how to convert these difficult-to-interpret effects into association results for shifts between two ancestries under an isoancestry constraint (holding an ancestry fraction constant) using post-estimation average marginal effects and explain their geometric interpretation. We found that increasing proportion of African ancestry was associated with increased levels of excreted MPO in low-income household infants in three Northeastern Brazil studies, with a smaller negative secondary association of European ancestry, all under a tri-continental ancestry composition (African, European, Amerindian). While the maximum log(MPO) outcome variance explained by differences in genetic ancestry was modest at a few percent, we show evidence that these differences in heritability were context-dependent on measurement of MPO under active enteric infection. The results were attenuated by socio-economic status, but a signal remained. Overall, we found that African genomes carry additional alleles that enable a more intensive neutrophil response to enteric infection relative to European and Amerindian genomes, illuminating a possible host genetic background role in modulating immune response to enteric diseases and pathogens.",
  "abstract_shown": true,
  "affiliations": [
    "University of Virginia"
  ],
  "article_type": "PUBLISHAHEADOFPRINT",
  "arxiv": null,
  "author_total": 5,
  "authors": [
    {
      "affs": [
        0
      ],
      "name": "J. Mychaleckyj"
    },
    {
      "name": "A. Havt"
    },
    {
      "name": "U. Nayak"
    },
    {
      "name": "R. L. Guerrant"
    },
    {
      "name": "A. A. Lima"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/bbc84j8yfb182.bib",
  "cited_by": 0,
  "doi": "10.64898/2026.10.02.26364607",
  "fulltext_url": "https://www.medrxiv.org/content/10.64898/2026.10.02.26364607v1.full",
  "id": "bbc84j8yfb182",
  "issns": [],
  "landing_url": "https://www.medrxiv.org/content/10.64898/2026.10.02.26364607v1",
  "language": null,
  "licence": "CC-BY",
  "licence_label": "CC BY",
  "licence_source": "article",
  "licence_url": "https://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "medrxiv",
      "genetic and genomic medicine"
    ],
    [
      "openalex",
      "1311|Genetic Associations and Epidemiology"
    ]
  ],
  "openalex": "W7220467260",
  "pdf_url": "https://www.medrxiv.org/content/10.64898/2026.10.02.26364607v1.full.pdf",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-02",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/bbc84j8yfb182.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:20:06Z",
      "native_id": "10.64898/2026.10.02.26364607",
      "source": "medrxiv",
      "url": "https://www.medrxiv.org/content/10.64898/2026.10.02.26364607v1"
    }
  ],
  "subjects": [
    {
      "field": "medicine",
      "origin": "medrxiv:genetic and genomic medicine",
      "subfield": "human-genetics"
    }
  ],
  "title": "Compositional analysis of genetic ancestry shows that relative proportion of African ancestry is positively associated with fecal myeloperoxidase in Brazilian infants",
  "title_text": "Compositional analysis of genetic ancestry shows that relative proportion of African ancestry is positively associated with fecal myeloperoxidase in Brazilian infants",
  "type": "preprint",
  "updated_at": "2026-10-30T12:20:06Z",
  "url": "https://research.draconitic.com/paper/bbc84j8yfb182",
  "venue": "medRxiv",
  "versions": []
}