Non-Invasive Detection of Iron Deficiency Anaemia in Children (Aged 0–5 Years): A Systematic Search of Available Tools for Widespread Application

Abstract

Iron deficiency anaemia (IDA) remains the most prevalent nutritional disorder affecting children globally, with disproportionate consequences for those aged 0–5 years, a period of critical neurodevelopmental growth. Despite decades of targeted interventions, IDA continues to affect hundreds of millions of young children in low- and middle-income countries (LMICs), where conventional venepuncture-based diagnostic approaches face formidable barriers of cost, infrastructure, trained personnel, and child compliance. This narrative review systematically searches and synthesises the available non-invasive and near-non-invasive tools for the detection of IDA in children aged 0–5 years, with attention to their feasibility for widespread deployment in resource-limited settings. Literature searches were conducted across multiple academic databases including PubMed, Scopus, Web of Science, and Google Scholar. The search was conducted in the period January to March 2025. The review examines a spectrum of approaches ranging from subjective clinical pallor assessment and point-of-care colorimetric devices such as the HemoCue, to transcutaneous optical spectroscopy, smartphone-based digital imaging applications, machine learning-enabled diagnostic platforms, and emerging wearable biosensor technologies. Evidence is evaluated with respect to analytical accuracy, cost-effectiveness, operational simplicity, regulatory status, and scalability in diverse health-system contexts. The findings indicate that, whilst no single non-invasive modality yet meets all criteria for universal deployment, smartphone-based approaches and machine learning-assisted imaging systems show particular promise for community-level screening, especially where integration with existing mobile health infrastructure is feasible. Ongoing challenges include validation in diverse paediatric populations, performance under varying ambient conditions, and the absence of standardised benchmarks for screening sensitivity and specificity. The review concludes that a multi-modal, tiered approach combining non-invasive screening with confirmatory laboratory testing represents the most pragmatic pathway toward reducing the diagnostic gap for IDA in young children worldwide.