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Assessing Total Fluoride Intake in Children: Reliability of Commonly Used Methods.
Fatemeh Vida Zohoori1, Marilia Afonso Rabelo Buzalaf2, Anne Maguire3
1School of Health and Life Sciences, Teesside University, Middlesbrough, UK.
Community Dentistry and Oral Epidemiology
|August 22, 2025
Summary
Questionnaires and urinary biomarkers show poor agreement for assessing children's total daily fluoride intake (TDFI). This study highlights significant discrepancies, especially at higher exposure levels, indicating a risk of misclassification in fluoride exposure assessments.
Area of Science:
- Biomarkers and Exposure Assessment
- Pediatric Nutrition and Public Health
- Environmental Health and Toxicology
Background:
- Estimating fluoride exposure in children typically relies on questionnaires or urinary biomarkers.
- No prior studies have directly compared these methods for classifying fluoride intake levels.
- Accurate assessment is crucial for understanding potential health impacts and guiding public health strategies.
Purpose of the Study:
- To compare the agreement and classification consistency between questionnaire- and urinary-based methods for assessing total daily fluoride intake (TDFI) in children aged 4-7 years.
- To evaluate discrepancies in classifying children into low to high fluoride intake categories.
- To identify potential biases associated with each assessment method.
Main Methods:
- A cross-national study involving 104 children (UK, Brazil, Chile) exposed to different fluoridation modalities.
- Collection of 24-hour urine samples and completion of validated dietary/oral hygiene questionnaires.
- Calculation of TDFI from diet and toothpaste, and prediction of TDFI from 24-hour urinary fluoride excretion (24h-UFE) using WHO guidelines.
- Statistical analysis included paired t-tests, Bland-Altman analysis for continuous data, and Cohen's kappa for categorical agreement.
Main Results:
- The questionnaire method yielded a higher mean TDFI (0.072 mg/kgbw/day) compared to the urine method (0.058 mg/kgbw/day, p=0.01).
- Bland-Altman analysis indicated good agreement at lower intake levels (<0.10 mg/kgbw/day) but increased variability at higher levels.
- Cohen's kappa showed minimal agreement (κ=0.034) between the methods, suggesting classifications were largely due to chance, with notable discrepancies in the fluoridated milk group.
Conclusions:
- Significant discrepancies and minimal agreement exist between questionnaire and urinary methods for assessing TDFI in children.
- The risk of misclassification is particularly high in groups with higher fluoride exposure.
- Further research is needed to develop and validate combined assessment approaches for accurate fluoride exposure evaluation in pediatric populations.
