1 / 12

Validity and Reproducibility of Exposure Measurements: The Method of Triads

Validity and Reproducibility of Exposure Measurements: The Method of Triads. Edmond K. Kabagambe and Hannia Campos Harvard School of Public Health. Suggested reading. Kaaks, RJ. (1997). Am J Clin Nutr 65:1232S-1239S Ocke and Kaaks (1997). Am J Clin Nutr 65:1240S-1245S

hermione
Download Presentation

Validity and Reproducibility of Exposure Measurements: The Method of Triads

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Validity and Reproducibility of Exposure Measurements: The Method of Triads Edmond K. Kabagambe and Hannia Campos Harvard School of Public Health

  2. Suggested reading • Kaaks, RJ. (1997). Am J Clin Nutr 65:1232S-1239S • Ocke and Kaaks (1997). Am J Clin Nutr 65:1240S-1245S • Kabagambe et al (2001). Am J Epidemiol 154:1126-1135

  3. Objectives • Define the method of triads (MOT) • Describe the MOT and interpretation of the resulting validity coefficients • Give an example to illustrate the application of the MOT

  4. Exposure in Epidemiology • Exposure can be • Discrete e.g. Yes or No • Continuous e.g. plasma cholesterol, lycopene intake • Measurement error is common with continuous exposures

  5. An example for illustration • A researcher wants to measure dietary intake of lycopene • Three methods are available • Food-frequency questionnaire • 24-hr dietary recalls/records (DR) • Biomarker (plasma concentrations)

  6. We obtain 3 observed and 1 latent exposure parameters • FFQ estimate (Q) • Average of dietary recalls (R) • Biomarker measurement (M) • True, but unknown, exposure i.e. lycopene intake (T)

  7. Q rQR rQM T R M rRM Relation between true exposure (T) and 3 surrogate measures (Q, R, and M)

  8. Validity coefficients (1) • How are they computed? • What do they measure?

  9. Validity coefficients (2) • How are they interpreted for validity or reproducibility? • Can they have confidence intervals?

  10. Example on the validation of lycopene intake • Step 1: Compute correlations • Step 2: Compute VCs • Step 3: Compare VC • Step 4: Compute 95% confidence limits

  11. Example on the validation of lycopene intake continued • Step 1: Compute correlations • Step 2: Compute VCs • Step 3: Compare VC • Step 4: Compute 95% confidence limits

  12. Conclusion • The method of triads is a simple technique for assessing validity and reproducibility of continuous exposure measurements. • Although described for nutritional epidemiological studies, this method could also be applied to other continuous exposures.

More Related