Performance of iron spot test with Arabic bread made from fortified white wheat flour


Background: The iron spot test (IST) is a simple qualitative technique for determining the presence of added iron in fortified flour. IST performance in bread has never been investigated. If found to perform well, the IST has the potential to provide a field-friendly method for testing bread and thus support the monitoring and evaluation of flour fortification programs.

Objective: To assess the performance of the IST in Arabic bread made from white wheat flour.

Methods: Bread samples were collected from 1,737 households during a national micronutrient survey in Jordan. A subsample of Arabic bread (n = 44) was systematically selected for testing by both the IST and spectrophotometry (criterion reference). Performance measures (sensitivity, specificity, and positive and negative predictive values) were calculated using five cutoffs to define the presence of added iron, including ≥ 15.0 ppm (approximate level of natural iron in Arabic bread) and four additional cutoffs based on test performance.

Results: The iron contents of samples testing negative by IST ranged from 10.4 to 18.4 ppm, with one outlier at 41.0 ppm, which was excluded from subsequent analyses. The iron contents of samples testing positive by IST ranged from 16.1 to 38.4 ppm. With the exception of negative predictive values for the two lowest cutoffs (≥ 15.0 and ≥ 16.1 ppm), all performance measures exceeded 83.3%.

Conclusions: These results show promise for the IST as an inexpensive, field-friendly method for testing bread that could have a useful role in the monitoring and evaluation process for flour fortification programs.

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