VALIDATION OF A SIMPLE, MANUAL URINARY IODINE METHOD FOR ESTIMATING THE PREVALENCE OF IODINE-DEFICIENCY DISORDERS, AND INTERLABORATORY COMPARISON WITH OTHER METHODS

The measurement of urinary iodine in population-based surveys provides a biological indicator of the severity of iodine-deficiency disorders . We describe the steps performed to validate a simple, inexpensive, m anual urinary iodine acid digestion method, and compare the results us ing this method with those of other urinary iodine methods. Initially, basic performance characteristics were evaluated: the average recover y of added iodine was 100.4 +/- 8.7% ((x) over bar +/- SD), within-ass ay precision (CV) over the assay range 0-0.95 mu mol/L (0-12 mu g/dL) was < 6%, between-assay precision over the same range was < 12%, and a ssay sensitivity was 0.05 mu mol/L (0.6 mu g/dL). There were no appare nt effects on the method by thiocyanate, a known interfering substance . In a comparison with five other methods performed in four different laboratories, samples were collected to test the method performance ov er a wide range of urinary iodine values (0.04-3.7 mu mol/L, or 0.5-47 mu g/dL). There was a high correlation between all methods and the in terpretation of the results was consistent. We conclude that the simpl e, manual acid digestion method is suitable for urinary iodine analysi s.