The most appropriate way of sample collection for individualized detection of urinary iodine

Objective By studying the variation of individual urinary iodine concentration due to different ways of urine sample collection to optimize it for standard clinical evaluation. Methods Totally 20 healthy adults were recruited and their urine samples were collected as a random urine sample within 1 day, the 24 hour urine and morning urine samples within 5 successive days, respectively. The coefficient of variation in each group was calculated. Paired t test was used to compare the results of 24 hour urine with the results of random urine and that of morning urine samples, respectively. Results The range of individual coefficient of variation for random urine sample within one day was 12.5%-57.4%, while most of the coefficients of variation were around 30.39%. In contrast, the individual coefficients of variation of morning urine sample and 24 hour urine results within 5 days were 5.4%-26.0% and 3.4%-16.6% and most of them were at about 11.74% and 7.91%. The paired t test showed that the results of random urine sample were significantly different compared with that of 24 hour urine (t=-4.231, P < 0.05). On the other hand, there was also significant difference for the results of morning urine compared with that of 24 hour urine (t= 3.884, P < 0.05). Conclusion This study suggests that 24 hour urine is the most appropriate way of sample collection for individualized detection of urinary iodine. Key words: Arsenic cerium catalytic spectrophotometry; Urine; Iodine; Urinary sample collection