By Noor Khan, Senior Technical Advisor, Food Fortification and Universal Salt Iodization
About iodine deficiency disorders
Iodine deficiency is a major cause of preventable brain damage in childhood.
It reduces a person’s intellectual capacity, mental development and growth, impacting their life forever at home, school and work. Iodine deficiency disorders (IDD) continue to be a public health problem in populations globally, particularly pregnant women and young children.
Over the past 20 years, countries worldwide have implemented salt iodization – an affordable solution to prevent iodine deficiency and its consequent iodine deficiency disorders.
Iodizing salt has proven to be the most effective, simple and inexpensive weapon against iodine deficiency disorders and MI has been working successfully with countries to ensure adequately iodized salt. However, despite being on the verge of eliminating IDD, more work is needed as 54 countries are still considered iodine deficient.
It is no longer sufficient to merely verify the presence or absence of iodine in salt in our efforts to provide adequately iodized salt as a way to fight iodine deficiency disorders.
To properly support monitoring efforts – and sustainability – of iodine levels in salt, it is critical to know the actual amount of iodine we add to salt, so we can judge whether the salt is adequately iodized.
Currently, laboratory-based analytical methods, such as iodometric titration, exists that quantitatively assess iodine content in salt. Yet, it is more challenging to perform such assessments at the level of production, importation and consumption because providing laboratory facilities, equipment and skill personnel is often difficult in resource constrained situations.
To properly support sustainability and monitoring of this critical IDD intervention, laboratory technicians and non-technicians around the world need access to simple and reliable methods of assessing iodine concentrations in salt during fieldwork.
Quantitative rapid test kits – a potential solution in the field
While for most settings iodometric titration has been accepted as the reference method, a number of apparently more user and field friendly analytical devices for the quantitative assessment of salt iodine content – called quantitative rapid test kits or quantRTK – have become available recently.
These devices are tailor-made for testing salt iodine content in the field. They do not require the existence of a physical laboratory setting, equipment and skilled staff to conduct the tests properly, thus are provide results quickly and at much lower costs.
However, the question remains as to which device will best serve program needs, especially since quantRTK devices are new and a number of different types used in different programs worldwide.
To address this issue, I – along with a team of 10 researchers from Switzerland, Burkina Faso, and South Africa – compared five currently available quantRTKs in terms of performance both in the laboratory and in the field. We wanted the results to provide evidence-based guidance to professional NGO staff and the UN, as well as to governments and industry around the world.
Five devices assessed
- iCheckTM (Germany): A portable photometer that calculates iodine content in mg/L. The kit includes nearly everything needed to conduct the test; users must supply purified water and plastic flasks.
- ID-ERTKTM (India): Device comes with a power plug, scale, quartz cuvette and other lab hardware. The user prepares the reagent solutions.
- I-ReaderTM (Thailand): A portable spectrophotometer calculates iodine levels in salt in mg/kg. Samples can be kept in test tubes for visual comparison for several days.
- saltPADTM (USA): Currently in beta-testing, this product uses paper cards to calculate iodine content in salt.
- WYDTM iodine checker (China): This device uses the same methodology as iCheckTM,
ID-ERTKTM and I-ReaderTM. The test kit comes with device and power plug, some lab hardware and a manual. The user prepares the reagent solutions.
The overall rating for each device was determined by:
- Suitability for low resource settings: cost, availability of reagents
- User-friendliness: use of hazardous reagents, skills/infrastructure required
- Field readiness: waste disposal, ruggedness, mobility
- Analytical performance: sample throughput, accuracy/comparability
Most of the devices tested showed acceptable laboratory performance but, for some of the devices, use by non-technicians revealed poor performance when working using routine procedures.
In addition, we also took care to evaluate the “softer” parameters, including cost, skills required and device ruggedness, as objectively as possible to ensure a fair and accurate rating of each device.*
The full methods and dataset can be found at http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0138530
- The iCheckTM and I-ReaderTM were the most reliable devices in terms of analytical performance, consistency and ease-of-use. Among these two, the I-ReaderTM is more affordable in terms of device and reagents’ cost but needs minor apparatus design modification to be fully recommended. In addition to the higher cost, iCheckTM requires a computer to calculate results and produces additional waste i.e. needles and glass vials but comes with a finished design.
- SaltPADTM, a newly developed paper based method is still in the process of full development.
- WYDTM and the ID-ERTKTM have acceptable performance but their advantage over titration is not apparent because like titration these require basic laboratory setting to prepare solutions and skills staff to perform the tests. Additionally the ID_ERTKTM has a very narrow measuring range and is still in the early stage of commercialization.
Both iodometric titration and quantRTK are subject to error, and should accompany appropriate quality assurance procedures to help ensure that measurement issues are identified in time.
The bottom line is, in the field quantRTK devices simplify salt iodine content monitoring, reduce costs associated with monitoring, and increase efficiency, which can help build program sustainability and – in the long term – help us reach the end of iodine deficiency disorders.
- The results are based on the study and do not represent or endorse a particular product, and may not necessarily agree with other findings in the future.