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FEASIBILITY OF USING ELECTRONIC RAPID TESTING KITS
(eRTK) FOR IMPROVED MONITORING OF SALT PROCESSORS
Jha R1, Dey S1 and Mannar V2.
1
The Micronutrient Initiative, India
2
The Micronutrient Initiative, Ottawa, Canada
ABSTRACT
Background: Small and medium-scale salt producers
do not have laboratories in the vicinity of the production
line resulting in time-lag between sample collection,
testing and incorporation of corrective guidance. This
lag increases the risk of producing non-standard iodized
salt.
Objective: To assess accuracy during field-use of an
electronic Rapid Testing Kit (eRTK) as a method for
testing iodine content. Under the study, a total of 3,198
iodized salt samples (504 samples of crystals, 1,596
crushed and 1,098 samples of crushed and washed salt)
were tested using 15 eRTKs in 15 different sites in six
states of India.
Results: In comparison with the gold standard
(Iodometric titration), eRTK has a sensitivity of 76.3%,
specificity of 81.9%, positive predictive value of 79.5%
and negative predictive value of 79%. The cut off point in
eRTK was ±3 parts per million (ppm) as compared to the
titration method. eRTK test cost 25% of titration cost.
Conclusions: The eRTK was found to be a reasonably
accurate and portable testing kit suitable for use in
different field settings.
SALT PRODUCTION AND IODINE TESTING
SCENARIO IN INDIA
Total production of salt in
the country
(million metric ton): 24.5
Total edible salt
(million metric ton): 6.2
Share of edible salt covered
in study: 34% of India’s total
iodised salt production
Highest salt producing
State: Gujarat
Type of salts available:
Crystal, Crushed, Crushed and washed, Refined salt
Types of iodization processes: Salt Refinery, Salt
Upgradation plant, Mobile salt Iodization plant and Knap
Sac
Gold Standard of testing: Iodometric Titration
Test introduced here: Electronic Rapid Testing Kit
(eRTK, Innovative Design).
METHOD
There are four major iodization processes for nonrefined salt. The instrument works best for the Salt
Upgradation Plant . Currently, the salt Iodization plants
and Knap Sacs (spray used for iodization) are getting
upgraded to salt upgradation plants.
The cut off point was ±3 parts per million (ppm) in eRTK
as compared to the titration method.
Samples
A total of 3,198 salt samples
from 6 states of India were
tested.
3 types of salt:
1. Crystal (504 samples).
2. Crushed (1,596 samples).
3. Crushed and washed
(1,098 samples).
Testing
1. 15 eRTKs units located at 15
different centres
2. Tested by individual
chemists.
3. 20 g of iodized salt taken for
iodine estimation using
iodometric titration method.
4. The remaining salt was used
for estimation through eRTK.
Diagnostic screening
Indicators computed in Excel
1.Sensitivity=TP/(TP+FN)*100
2. Specificity= TN/(TN+FP)*100
3. Positive Predictive Value=
TP/(TP+FP)*100 and
4. Negative Predictive Value=
TN/(TN+FN)*100
Where, TP: True Positives, FP: False
Positives, TN: True Negatives and FN:
False Negatives
CONCLUSION
The result of the study suggest that eRTK produces
reasonably accurate results in field settings. It is not,
however, a replacement of Iodometric titration, which is
the “Gold Standard”.
eRTK’s light weight and battery-powered option makes it
highly useful in diverse field sites.
RESULT
FIGURE 1: DIAGNOSTIC SCREENING
INDICATORS OF eRTK COMPARED TO
TITRATION METHOD BY TYPES OF SALT
Access to immediate iodine results in the field allows
instant feedback and rapid corrections to processing
methods.
Cost of testing iodized salt samples using eRTK is 25% to
that of Iodometric titration.
ACKNOWLEDGEMENT
We would like to acknowledge the support from
Government of Canada through the Department of
Foreign Affairs, Trade and Development and Innovative
Design, Chennai, India (developer of eRTK) for their
efforts to achieve desired results.
OBJECTIVE
To assess accuracy during field-use of an Electronic Rapid
Testing Kit (eRTK) for assessing iodine content of salt in
the production line, to monitor and maintain iodine levels
during its production, particularly in small and medium
scale production units.
Note:
Point estimates presented alongwith 95% confidence
intervals.
BACKGROUND
• Quality control is a process to detect and correct
production default from specified standards during
actual processing. In salt iodization units, iodized salt
samples are collected and tested through iodometric
titration in a laboratory attached to the production unit.
• Small and medium-scale producers do not have these
adjacent laboratories. The time-lag between sample
collection, testing, and incorporation of corrective
guidance increases the risk of producing non-standard
iodized salt.
• MI has been working with ~300 small and medium
scale salt producers to improve production method and
quality control. They collectively produce ~ 2.1 million
metric ton comprising 34% of India’s iodized salt
production.
• eRTK was developed as an instrument designed
specifically as a more rapid method of measuring
iodine levels in salt, particularly in small-scale
production sites. It uses the absorbing characteristics
of iodine-starch blue compound and applying the BeerLambert Law.
FIGURE 2: DIAGNOSTIC SCREENING
INDICATORS OF eRTK COMPARED TO
TITRATION METHOD BY IODIZATION
PROCESSES
Note:
The range of sensitivity, specificity, Positive Predictive
Value (PPV) and Negative Predictive Value (NPV) vary
from 70-90 per cent among the three types of salts, which
shows that it works reasonably well for the three types of
salts.
Correspondence: Ranjan Kumar Jha; rkumarjha@micronutrient.org