Bio


Madelena Ng is a postdoctoral scholar working with Dr. Tina Hernandez-Boussard at the Stanford Center for Biomedical Informatics Research (BMIR).

Professional Education


  • DrPH, University of California, Berkeley, Public Health with DE in Science and Technology Studies
  • MPH, University of California, Los Angeles, Epidemiology
  • BS, University of California, Los Angeles, Neuroscience with minor in Asian American Studies

Stanford Advisors


All Publications


  • The AI life cycle: a holistic approach to creating ethical AI for health decisions. Nature medicine Ng, M. Y., Kapur, S., Blizinsky, K. D., Hernandez-Boussard, T. 2022

    View details for DOI 10.1038/s41591-022-01993-y

    View details for PubMedID 36163298

  • Usability, inclusivity, and content evaluation of COVID-19 contact tracing apps in the United States JOURNAL OF THE AMERICAN MEDICAL INFORMATICS ASSOCIATION Blacklow, S. O., Lisker, S., Ng, M. Y., Sarkar, U., Lyles, C. 2021; 28 (9): 1982-1989

    Abstract

    We evaluated the usability of mobile COVID-19 contact tracing apps, especially for individuals with barriers to communication and limited digital literacy skills. We searched the Apple App Store, Google Play, peer-reviewed literature, and lay press to find contact tracing apps in the United States. We evaluated apps with a framework focused on user characteristics and user interface. Of the final 26 apps, 77% were on both iPhone and Android. 69% exceeded 9th grade readability, and 65% were available only in English. Only 12% had inclusive illustrations (different genders, skin tones, physical abilities). 92% alerted users of an exposure, 42% linked to a testing site, and 62% linked to a public health website within 3 clicks. Most apps alert users of COVID-19 exposure but require high English reading levels and are not fully inclusive of the U.S. population, which may limit their reach as public health tools.

    View details for DOI 10.1093/jamia/ocab093

    View details for Web of Science ID 000692577000022

    View details for PubMedID 34022053

    View details for PubMedCentralID PMC8194594

  • Smartphone-Based Geofencing to Ascertain Hospitalizations CIRCULATION-CARDIOVASCULAR QUALITY AND OUTCOMES Nguyen, K. T., Olgin, J. E., Pletcher, M. J., Ng, M., Kaye, L., Moturu, S., Gladstone, R. A., Malladi, C., Fann, A. H., Maguire, C., Bettencourt, L., Christensen, M. A., Marcus, G. M. 2017; 10 (3)

    Abstract

    Ascertainment of hospitalizations is critical to assess quality of care and the effectiveness and adverse effects of various therapies. Smartphones, mobile geolocators that are ubiquitous, have not been leveraged to ascertain hospitalizations. Therefore, we evaluated the use of smartphone-based geofencing to track hospitalizations.Participants aged ≥18 years installed a mobile application programmed to geofence all hospitals using global positioning systems and cell phone tower triangulation and to trigger a smartphone-based questionnaire when located in a hospital for ≥4 hours. An in-person study included consecutive consenting patients scheduled for electrophysiology and cardiac catheterization procedures. A remote arm invited Health eHeart Study participants who consented and engaged with the study via the internet only. The accuracy of application-detected hospitalizations was confirmed by medical record review as the reference standard. Of 22 eligible in-person patients, 17 hospitalizations were detected (sensitivity 77%; 95% confidence interval, 55%-92%). The length of stay according to the application was positively correlated with the length of stay ascertained via the electronic medical record (r=0.53; P=0.03). In the remote arm, the application was downloaded by 3443 participants residing in all 50 US states; 243 hospital visits at 119 different hospitals were detected through the application. The positive predictive value for an application-reported hospitalization was 65% (95% confidence interval, 57%-72%).Mobile application-based ascertainment of hospitalizations can be achieved with modest accuracy. This first proof of concept may ultimately be applicable to geofencing other types of prespecified locations to facilitate healthcare research and patient care.

    View details for DOI 10.1161/CIRCOUTCOMES.116.003326

    View details for Web of Science ID 000397591500005

    View details for PubMedID 28325751

    View details for PubMedCentralID PMC5363280

  • Continuous daily assessment of multiple sclerosis disability using remote step count monitoring JOURNAL OF NEUROLOGY Block, V. J., Lizee, A., Crabtree-Hartman, E., Bevan, C. J., Graves, J. S., Bove, R., Green, A. J., Nourbakhsh, B., Tremblay, M., Gourraud, P., Ng, M. Y., Pletcher, M. J., Olgin, J. E., Marcus, G. M., Allen, D. D., Cree, B. C., Gelfand, J. M. 2017; 264 (2): 316-326

    Abstract

    Disability measures in multiple sclerosis (MS) rely heavily on ambulatory function, and current metrics fail to capture potentially important variability in walking behavior. We sought to determine whether remote step count monitoring using a consumer-friendly accelerometer (Fitbit Flex) can enhance MS disability assessment. 99 adults with relapsing or progressive MS able to walk ≥2-min were prospectively recruited. At 4 weeks, study retention was 97% and median Fitbit use was 97% of days. Substudy validation resulted in high interclass correlations between Fitbit, ActiGraph and manual step count tally during a 2-minute walk test, and between Fitbit and ActiGraph (ICC = 0.76) during 7-day home monitoring. Over 4 weeks of continuous monitoring, daily steps were lower in progressive versus relapsing MS (mean difference 2546 steps, p < 0.01). Lower average daily step count was associated with greater disability on the Expanded Disability Status Scale (EDSS) (p < 0.001). Within each EDSS category, substantial variability in step count was apparent (i.e., EDSS = 6.0 range 1097-7152). Step count demonstrated moderate-strong correlations with other walking measures. Lower average daily step count is associated with greater MS disability and captures important variability in real-world walking activity otherwise masked by standard disability scales, including the EDSS. These results support remote step count monitoring as an exploratory outcome in MS trials.

    View details for DOI 10.1007/s00415-016-8334-6

    View details for Web of Science ID 000393902500012

    View details for PubMedID 27896433

    View details for PubMedCentralID PMC5292081

  • IRF8 acts in lineage-committed rather than oligopotent progenitors to control neutrophil vs monocyte production BLOOD Yanez, A., Ng, M. Y., Hassanzadeh-Kiabi, N., Goodridge, H. S. 2015; 125 (9): 1452-1459

    Abstract

    Interferon regulatory factor 8 (IRF8) is a key regulator of myelopoiesis in mice and humans. IRF8-deficient mice exhibit increased neutrophil numbers but defective monocyte and dendritic cell (DC) production. It has therefore been hypothesized that IRF8 regulates granulocyte vs monocyte/DC lineage commitment by oligopotent progenitors. Alternatively, IRF8 could control the differentiation of lineage-committed progenitors. In this study, we defined the role of IRF8 in lineage commitment and neutrophil vs monocyte differentiation using a novel sorting strategy that for the first time allows us to separate oligopotent granulocyte-monocyte progenitors (GMPs) and their lineage-committed progeny: granulocyte progenitors (GPs) and monocyte progenitors (MPs). We show that IRF8 is highly expressed by both GPs and MPs, but not GMPs, and is not required for GP or MP production by GMPs. In fact, IRF8-deficient mice have more GPs and MPs. This is not due to IRF8-mediated suppression of GP and MP production by GMPs, but rather to selective effects in GPs and MPs. We identify roles for IRF8 in regulating progenitor survival and differentiation and preventing leukemic cell accumulation. Thus, IRF8 does not regulate granulocytic vs monocytic fate in GMPs, but instead acts downstream of lineage commitment to selectively control neutrophil and monocyte production.

    View details for DOI 10.1182/blood-2014-09-600833

    View details for Web of Science ID 000350820900018

    View details for PubMedID 25597637

  • Detection of a TLR2 agonist by hematopoietic stem and progenitor cells impacts the function of the macrophages they produce EUROPEAN JOURNAL OF IMMUNOLOGY Yanez, A., Hassanzadeh-Kiabi, N., Ng, M. Y., Megias, J., Subramanian, A., Liu, G. Y., Underhill, D. M., Luisa Gil, M., Goodridge, H. S. 2013; 43 (8): 2114-2125
  • Preferential Biological Processes in the Human Limbus by Differential Gene Profiling PLOS ONE Nakatsu, M. N., Vartanyan, L., Vu, D. M., Ng, M. Y., Li, X., Deng, S. X. 2013; 8 (4): e61833

    Abstract

    Corneal epithelial stem cells or limbal stem cells (LSCs) are responsible for the maintenance of the corneal epithelium in humans. The exact location of LSCs is still under debate, but the increasing need for identifying the biological processes in the limbus, where LSCs are located, is of great importance in the regulation of LSCs. In our current study we identified 146 preferentially expressed genes in the human limbus in direct comparison to that in the cornea and conjunctiva. The expression of newly identified limbal transcripts endomucin, fibromodulin, paired-like homeodomain 2 (PITX2) and axin-2 were validated using qRT-PCR. Further protein analysis on the newly identified limbal transcripts showed protein localization of PITX2 in the basal and suprabasal layer of the limbal epithelium and very low expression in the cornea and conjunctiva. Two other limbal transcripts, frizzled-7 and tenascin-C, were expressed in the basal epithelial layer of the limbus. Gene ontology and network analysis of the overexpressed limbal genes revealed cell-cell adhesion, Wnt and TGF-β/BMP signaling components among other developmental processes in the limbus. These results could aid in a better understanding of the regulatory elements in the LSC microenvironment.

    View details for DOI 10.1371/journal.pone.0061833

    View details for Web of Science ID 000317911500070

    View details for PubMedID 23630617

    View details for PubMedCentralID PMC3632514

  • Wnt/beta-Catenin Signaling Regulates Proliferation of Human Cornea Epithelial Stem/Progenitor Cells INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE Nakatsu, M. N., Ding, Z., Ng, M. Y., Truong, T. T., Yu, F., Deng, S. X. 2011; 52 (7): 4734-4741

    Abstract

    To investigate the expression and role of the Wnt signaling pathway in human limbal stem cells (LSCs).Total RNA was isolated from the human limbus and central cornea. Limbal or cornea-specific transcripts were identified through quantitative real-time PCR. Protein expression of Wnt molecules was confirmed by immunohistochemistry on human ocular tissue. Activation of Wnt signaling using lithium chloride was achieved in vitro and its effects on LSC differentiation and proliferation were evaluated.Expression of Wnt2, Wnt6, Wnt11, Wnt16b, and four Wnt inhibitors were specific to the limbal region, whereas Wnt3, Wnt7a, Wnt7b, and Wnt10a were upregulated in the central cornea. Nuclear localization of β-catenin was observed in a very small subset of basal epithelial cells only at the limbus. Activation of Wnt/β-catenin signaling increased the proliferation and colony-forming efficiency of primary human LSCs. The stem cell phenotype was maintained, as shown by higher expression levels of putative corneal epithelial stem cell markers, ATP-binding cassette family G2 and ΔNp63α, and low expression levels of mature cornea epithelial cell marker, cytokeratin 12.These findings demonstrate for the first time that Wnt signaling is present in the ocular surface epithelium and plays an important role in the regulation of LSC proliferation. Modulation of Wnt signaling could be of clinical application to increase the efficiency of ex vivo expansion of corneal epithelial stem/progenitor cells for transplantation.

    View details for DOI 10.1167/iovs.10-6486

    View details for Web of Science ID 000293332500107

    View details for PubMedID 21357396

    View details for PubMedCentralID PMC3175950