Benchmarking Rapid Screening Kits versus Iodometric Titration for Iodine Quantification in Household Salt

Iodine deficiency remains a significant public health issue. Despite universal salt iodization efforts in Razavi Khorasan Province, accurate monitoring of iodine content in salt continues to pose challenges. This study evaluates the precision and accuracy of rapid screening kits compared to iodometric titration-the gold standard-for quantifying iodine in household salt, aiming to improve monitoring strategies in the region.

This cross-sectional study was conducted in 2024, collecting 153 household salt samples from areas affiliated with Mashhad University of Medical Sciences. Iodine content was measured using the Waheb iodine test kit, which provides both qualitative and quantitative results. These were compared with iodometric titration. Iodine levels were classified according to WHO/UNICEF/IGN guidelines and Iranian National Standards. Statistical analysis included sensitivity, specificity, positive and negative predictive values, and Cohen's kappa coefficient to assess agreement between methods.

The mean (SD) iodine concentration measured by the rapid screening kits was 35.75 (13.85) µg/g, while iodometric titration showed 58.38 (31.45) µg/g. The rapid screening kits demonstrated a sensitivity of 84.91% (95% CI: 72.41-93.25%), specificity of 20.00% (95% CI: 12.67-29.18%), positive predictive value of 80.94%, and a negative predictive value of 24.88%. Agreement between methods was poor (Cohen's kappa = 0.037).

Despite their convenience, rapid screening kits show limited reliability in accurately assessing iodine levels in table salt. The significant discrepancy with iodometric titration highlights the need for improved quality control and development of more accurate rapid testing tools to effectively prevent and control iodine deficiency.