In-Country Method Validation of a Paper-Based, Smartphone-Assisted Iron Sensor for Corn Flour Fortification Programs.

Anna W Waller,Juan E Andrade Laborde,Marcela Gaytán-Martínez

doi:10.3390/foods11030276

Abstract

Food fortification in low-income settings is limited due to the lack of simple quality control sensing tools. In this study, we field validated a paper-based, smartphone-assisted colorimetric assay (Nu3Px) for the determination of iron in fortified flours against the gold standard method, atomic emission spectrometry (AES). Samples from commercial brands (n = 6) were collected from supermarkets, convenience stores, and directly from companies in Mexico and characterized using both Nu3Px and AES. Nu3Px’s final error parameters were quantified (n = 45) via method validation final experiments (replication and comparison of methods experiment). Qualitative pilot testing was conducted, assessing Nu3Px’s accept/reject batch decision making (accept ≥ 40 μg Fe/g flour; reject < 40 μg Fe/g flour) against Mexico’s fortification policy. A modified user-centered design process was followed to develop and evaluate an alternative sampling procedure using affordable tools. Variation of iron content in Mexican corn flours ranged from 23% to 39%. Nu3Px’s random error was 12%, and its bias was 1.79 ± 9.99 μg Fe/g flour. Nu3Px had a true mean difference from AES equal to 0 and similar variances. AES and Nu3Px made similar classifications based on Mexico’s policy. Using simple, affordable tools for sampling resulted in similar output to the traditional sampling preparation (r = 0.952, p = 0.01). The affordable sample preparation kit has similar precision to using analytical tools. The sample preparation kit coupled with the smartphone app and paper-based assay measure iron within the performance parameters required for the application to corn flour fortification programs, such as in the case of Mexico.

Highlights

Micronutrient deficiencies continue to afflict populations living in low- and middleincome countries [1]
A sample prep kit that aligns with the World Health Organization (WHO)’s ASSURED guidelines was developed and pilot tested by comparing its error performance parameters to that of Nu3Px using conventional laboratory tools
Though most of the corn flours collected complied with current regulations, these samples failed to comply with theoretical fortification parameters recommended by experts for upper limits

Summary

Introduction

Micronutrient deficiencies continue to afflict populations living in low- and middleincome countries [1]. The food industry, as well as local governments, lack tools to monitor fortified food entering the different markets [3] This is partially due to the limited availability of affordable and valid analytical and sensing tools to support these efforts [4,5]. In the case of low-income settings, the World Health Organization (WHO) has provided guidance under the ASSURED criteria for the development of diagnostic technologies (Affordable, Sensitive, Specific, User friendly, Rapid and Robust, Equipment-free, and Deliverable to End Users). These criteria help guide developers in the design of more impactful sensing tools, especially within limited resource settings [8]

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Discussion

Conclusion