Assessment of biomarkers for carotenoids, tocopherols, retinol, vitamin B12 and folate in the Hispanic Community Health Study/Study of Latinos
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Measurement error is a major issue in self-reported diet that can distort diet-disease relationships. Serum biomarkers avoid the subjective bias in self-report. As part of the Hispanic Community Health Study/Study of Latinos (HCHS/SOL), self-reported diet was collected on all participants. Blood concentration biomarkers for carotenoids, tocopherols, retinol, vitamin B12 and folate were collected on a subset, as part of the Study of Latinos: Nutrition and Physical Activity Assessment Study (SOLNAS). We examine the relationship between biomarker levels, self-reported intake, ethnicity and other participant characteristics in this diverse population. We build prediction equations for ten nutritional biomarkers and evaluate whether there would be sufficient precision in these prediction equations to reliably detect an association with this exposure in a multivariable Cox model. This type of predicted exposure is commonly used to assess measurement-error corrected diet-disease associations using regression calibration; however, issues of power are rarely discussed. We used simulation to study the power of detecting the association between a true average concentration marker and a hypothetical incident survival outcome in the HCHS/SOL cohort using a predicted biomarker level whose measurement characteristics were similar to those observed for SOLNAS. Good power was observed for some nutrients; whereas, a low intra-class correlation coefficient contributed to poor power for others. Repeat measures improved the ICC; however, further research is needed to understand how best to realize the potential of these dietary biomarkers. This study provides a comprehensive examination of several nutritional biomarkers, characterizing their associations with subject characteristics and the influence the measurement characteristics have on the power to detect associations with health outcomes.
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