Validity and Reproducibility of Exposure Measurements: The Method of Triads Edmond K. Kabagambe and...
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Transcript of Validity and Reproducibility of Exposure Measurements: The Method of Triads Edmond K. Kabagambe and...
![Page 1: Validity and Reproducibility of Exposure Measurements: The Method of Triads Edmond K. Kabagambe and Hannia Campos Harvard School of Public Health.](https://reader035.fdocuments.in/reader035/viewer/2022080915/56649e365503460f94b2662c/html5/thumbnails/1.jpg)
Validity and Reproducibility Validity and Reproducibility of Exposure Measurements: of Exposure Measurements: The Method of TriadsThe Method of Triads
Edmond K. Kabagambe and
Hannia Campos
Harvard School of Public Health
![Page 2: Validity and Reproducibility of Exposure Measurements: The Method of Triads Edmond K. Kabagambe and Hannia Campos Harvard School of Public Health.](https://reader035.fdocuments.in/reader035/viewer/2022080915/56649e365503460f94b2662c/html5/thumbnails/2.jpg)
Suggested readingSuggested 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
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ObjectivesObjectives
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
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Exposure in EpidemiologyExposure 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
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An example for illustrationAn 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)
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We obtain 3 observed and 1 We obtain 3 observed and 1 latent exposure parameterslatent exposure parameters
FFQ estimate (Q)Average of dietary recalls (R)Biomarker measurement (M)True, but unknown, exposure
i.e. lycopene intake (T)
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Relation between true Relation between true exposure (T) and 3 surrogate exposure (T) and 3 surrogate measures (Q, R, and M)measures (Q, R, and M)
T
Q
MR
rQMrQR
rRM
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Validity coefficients (1)Validity coefficients (1)
How are they computed?
What do they measure?
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Validity coefficients (2)Validity coefficients (2)How are they
interpreted for validity or reproducibility?
Can they have confidence intervals?
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Example on the validation of Example on the validation of lycopene intakelycopene intake
Step 1: Compute correlationsStep 2: Compute VCsStep 3: Compare VCStep 4: Compute 95%
confidence limits
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Example on the validation of Example on the validation of lycopene intake continuedlycopene intake continued
Step 1: Compute correlationsStep 2: Compute VCsStep 3: Compare VCStep 4: Compute 95%
confidence limits
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ConclusionConclusion
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.