A study about fluoride absorption could be affected by which factor that would most affect accuracy?

Correct answer: B. Differences in the concentration of fluoride in different natural water sources

• A. Test sensitivity/specificity is a methodological concern but less impactful than the biological confounding from varied baseline fluoride exposure.
• B. Correct. The major confounding variable in a fluoride absorption study would be DIFFERENCES IN NATURAL FLUORIDE CONCENTRATIONS in water sources. If different study populations have different background fluoride levels (some regions have naturally high fluoride), this directly affects measured fluoride absorption independently of the intervention studied.
• C. Altitude effects on fluoride absorption are not well-established as a major confounder in fluoride studies.
• D. Gender differences in fluoride absorption exist but are less significant than source concentration variability.