Use of Spot Urine Samples to Monitor Fluoride Intake.

Objectives: The WHO recommends monitoring of fluoride intake in countries with community fluoridation schemes as Colombia (salt fluoridation, 180-220 mg KF/Kg of salt, since 1989). The 24-h protocol is considered the gold standard, but some limitations have been reported. The aim of this study was to compare the fluoride measurements between the single spot urine samples and the 24-h urine samples protocol to monitor in children systemic fluoride intake through salt.
Methods: After IRB approval (UEB-558-2020) a randomized cross-over study was conducted in Bogotá-Colombia. 4- to 6-year-old children were recruited and provided urine samples in two sessions (one-week in-between sessions’ interval). Session A: 4-spot urine samples: (1) 3 hours after breakfast, (2) 3 hours after lunch, (3) last void of urine before going to bed, and (4) voided urine the following morning. Session B: Each child provided a 24-hour urine sample collected over four continuous intervals post-breakfast (PB): (1) 0-3h PB, (2) 3-6h PB, (3) 6-12h PB on Day 1 plus (4) nocturnal and first voided urine on Day 2. Descriptive analysis and individual and cumulative fluoride measurements derived from both urine schemes collection were compared.
Results: The final sample consisted of thirty-six participants (girls: 52.7%); mean weight: 17± Kg; mean height: 106± cm. Fluoride concentration in 24-h protocol showed the lowest concentration values in breakfast (0.79± ppm) and lunch (0.99± ppm) in day 1 and the highest values were found for dinner (1.26± ppm) (day 1) and breakfast (1.44± ppm) (day 2). The correspondent measurements from spot samples were: breakfast (1.09± ppm), lunch (1.48± ppm) in day 1, dinner (1.18± ppm) (day 1) and breakfast (1.26± ppm) (day 2). A generalized lineal model showed no differences between fluoride measurements among the two schemes (p>0.05).
Conclusions: Preliminary results suggest the use of spot samples as surrogates for 24-h urine samples.