How important is it that researchers account for variability between- and within-persons in biomonitoring levels to help guide design of epidemiology studies (beyond just “thinking about it”)? (please explain).

Answer Explanations

• Very important

  Expert 3
  Between- and within-person biomarker variability can result in exposure misclassification, which in turn attenuates the association between exposure and outcome. If not accounted for, this variability introduces noise into the data, weakening the study's conclusions. 
• Very important

  Expert 2
  It is crucial for researchers to account for both between- and within-person variability in biomonitoring levels when designing epidemiology studies, as biomonitoring measures the actual internal dose of chemicals or pollutants in the body, offering a more accurate reflection of real exposure than external exposure measurements alone. Properly addressing this variability is essential for optimizing sample size and the number of repeated measurements needed to detect true associations both efficiently and economically. Additionally, accounting for between-person variability improves the precision of effect estimates, leading to more reliable and valid study outcomes.
  
  

  By actively modeling both types of variability, researchers can more accurately measure internal exposure and design studies that yield more robust and actionable results. This is especially critical in biomonitoring, where accurate internal dose measurements are key to understanding the health impacts of environmental exposures.
• Very important

  Expert 7
  Answer to 4.2 applies here as well.  The main difference is that with biomonitoring studies one can compare designs that include more subjects vs more repeated measurements,
• Very important

  Expert 1
  Every study has a rate limiting step that either limits the number of subjects in a study or the number of assessments to be conducted on subjects as part of a biomonitoring study. The ability to be able to determine the "optimal" study given these logistical issues is very important in order to get more bang for your buck!
• Very important

  Expert 9
  Designing a study to account for both between- and within-person variability in biomonitoring levels (if estimates are available or can be generated in a pilot study), will help minimize misclassification and bias in estimates of association.  It will also help in getting the best balance between sample size and number of repeated measures for the available budget (and may help in securing funding to carry out the project).  It is so important in fact, that authors should be encouraged to consistently report values of between- and within-person variability in results sections or appendices of manuscripts, to help in design and evaluation of future studies. 
• Very important

  Expert 8
  Same as above, but maybe even more important here because of the dynamic nature of many biomarkers (of course highly biomarker dependent!).
• Very important

  Expert 5
  Same answer as above, expect we can hope to achieve more accurate measures of exposure using biomonitoring if the biosampling is correctly designed, and the toxicokinetics/dynamics are known.