Comparative Validation of Five Quantitative Rapid Test Kits for the Analysis of Salt Iodine Content: Laboratory Performance, User- and Field-Friendliness

<div><p>Background</p><p>Iodine deficiency has important health and development consequences and the introduction of iodized salt as national programs has been a great public health success in the past decades. To render national salt iodization programs sustainable and ensure adequate iodization levels, simple methods to quantitatively assess whether salt is adequately iodized are required. Several methods claim to be simple and reliable, and are available on the market or are in development.</p><p>Objective</p><p>This work has validated the currently available quantitative rapid test kits (quantRTK) in a comparative manner for both their laboratory performance and ease of use in field settings.</p><p>Methods</p><p>Laboratory performance parameters (linearity, detection and quantification limit, intra- and inter-assay imprecision) were conducted on 5 quantRTK. We assessed inter-operator imprecision using salt of different quality along with the comparison of 59 salt samples from across the globe; measurements were made both in a laboratory and a field setting by technicians and non-technicians. Results from the quantRTK were compared against iodometric titration for validity. An ‘ease-of-use’ rating system was developed to identify the most suitable quantRTK for a given task.</p><p>Results</p><p>Most of the devices showed acceptable laboratory performance, but for some of the devices, use by non-technicians revealed poorer performance when working in a routine manner. Of the quantRTK tested, the iCheck^® and I-Reader^® showed most consistent performance and ease of use, and a newly developed paper-based method (saltPAD) holds promise if further developed.</p><p>Conclusions</p><p>User- and field-friendly devices are now available and the most appropriate quantRTK can be selected depending on the number of samples and the budget available.</p></div

Summary of the results from the ‘system’ validation: inter-operator imprecision, expressed as coefficient of variation.

<p>^a three iodine levels were used (15.0, 29.6, 59.1 mg/kg) and the three CV’s are given in the order of increasing iodine concentration;</p><p>^b three iodine levels were used (20.0, 47.5, 90.4 mg/kg) and the three CV’s are given in the order of increasing iodine concentration;</p><p>^c outside of measuring range for more than one measurement and thus, n/d means not determined.</p><p>^d For the saltPAD, three types of interpretation of the results on the cards were done: interpretation by the operator, by an expert reader (a person from the device developer) and an image analysis software; the index provides the information which readings were used.</p><p>Summary of the results from the ‘system’ validation: inter-operator imprecision, expressed as coefficient of variation.</p

Schematic presentation of rating matrix employed.

<p>Schematic presentation of rating matrix employed.</p

Bland-Altman’s Limits of Agreement (LOA).

<p>^a Provides the number of samples with a valid quantitative result (i.e. not below or above the measuring range);</p><p>^b Difference between the reference method and the respective quantRTK;</p><p>^c Difference between the reference method and the quantRTK ±2 SD.</p><p>^d For the saltPAD, three types of interpretation of the results on the cards were done: interpretation by the operator, by an expert reader (a person from the device developer) and an image analysis software; the index provides the information which readings were used.</p><p>Bland-Altman’s Limits of Agreement (LOA).</p

Cohort characteristics.

<p>Cohort characteristics.</p

HLA associations with the remaining 15-mer OLP’s in CMV pp65, IE-1 and IE-2 that were targeted by ≥4% of the study cohort.

<p>HLA associations with the remaining 15-mer OLP’s in CMV pp65, IE-1 and IE-2 that were targeted by ≥4% of the study cohort.</p

Cohort characteristics.

<p>Cohort characteristics.</p

Validation of novel CD8+ T-cell epitopes in CMV using HLA-Class I tetramers.

<p>(A) Flow cytometry plot of CD8+ T-cell responses from a Durban cohort subject SK-251 (HLA-A*02:05, -A*30:01, -B*42:01, -B*58:01, -C*07:01, -C*017:01) to HLA-A*30:01-restricted IE-2-342/343 epitope-KK9 and an HLA-mismatched tetramer stain as a control. (B) Flow cytometry plot from a Durban cohort subject SK-331 (HLA-A*30:01, -A*66:01, -B*42:01, -B*58:02, -C*06:02, -C*017:01) to B*42:01-restricted pp65-66/67 epitope RL11 and an HLA-mismatched tetramer stain as a control. The plots show gated live CD3+ T-cells; the number shown above each gate is the percentage of live CD3+ CD8+ cells that are tetramer-specific.</p