Fighting iodine malnutrition with a paper test card

Author: Marya Lieberman

When kids don't get enough iodine in their diet, growth and brain development are stunted.  We developed a paper test card to help medical authorities and nutrition specialists monitor the need for iodine supplements in different populations.  Usually, this measurement requires a sophisticated lab  and costs a lot of money.  Many countries only assess their populations on a 5 or 10 year schedule.  The paper test card could help countries do this test much more frequently so they can monitor iodine nutrition programs.  

The paper test cards, like most of the laboratory tests, use a chemical that contains arsenic.  Arsenic is quite poisonous and some countries don't have good disposal facilities for toxic wastes, so we developed a remediation module to trap the arsenic so it can't leach out of the test card in a landfill.  The remediation module traps so much arsenic that the paper cards should be safe for disposal.  

Full details are available open access at PLOS-ONE

Journal citation:  Myers NM, Leung IC, McGee SW, Eggleson K, Lieberman M (2017) Green design of a paper test card for urinary iodine analysis. PLoS ONE 12(6): e0179716.

Abstract:  When young children do not receive adequate amounts of the micronutrient iodine in their diet, their growth and cognitive development can be impaired. Nearly every country in the world has programs in place to track iodine intake and provide supplemental iodine if needed, usually in the form of fortified salt. The iodine nutrition status of a population can be tracked by monitoring iodine levels in urine samples to see if the median value falls in the range of 100–300 micrograms of iodine per liter of urine (μg I/L), which indicates adequate or more than adequate iodine nutrition. Many low and middle-income countries (LMIC) do not have a laboratory capable of carrying out this challenging assay, so samples must be sent out for assay in external labs, which is expensive and time-consuming. In most LMIC, population iodine surveys are carried out every 5–10 years, which limits the utility of the data for program monitoring and evaluation. To solve this problem, we developed a field-friendly paper test card that uses the Sandell-Kolthoff reaction to measure urinary iodine levels. A blind internal validation study showed that 93% of samples (n = 60) of iodide in an artificial urine matrix were categorized correctly by visual analysis as deficient, adequate, or excessive for levels set forth by the World Health Organization. Quantitative measurements based on computer image analysis had an error of 40 ± 20 μg I/L (n = 35 for samples in the calibration range) and these results categorized 88% of the samples (n = 60) correctly. We employed lifecycle analysis principles to address the known toxicity of arsenic, which is an obligatory reagent in the Sandell-Kolthoff reaction. Disposal of the cards in a landfill (their most likely destination after use) could let arsenic leach into groundwater; toxicity characteristic leaching procedure (TCLP) tests showed that the level of arsenic leached from the cards was 28.78 ppm, which is above the United States Environmental Protection Agency’s limit of 5 parts per million for solid waste. We integrated a remediation module into the card. This module contains oxone, to oxidize As(III) to As(V) oxyacids, and the iron oxide goethite. TCLP testing showed that the leachable amount of arsenic was reduced by at least 97.6%—from 28.8 ppm to lower than 0.7 ± 0.7 ppm (n = 20). This upstream intervention rendered the test card suitable for landfilling while retaining its functionality to perform a critical public health evaluation.