Analytical and biological variability in biomarker measurement in the Hispanic Community Health Study/Study of Latinos.

Background: Biomarker variability, which includes within-individual variability (CV _I ), between-individual variability (CV _G ) and methodological variability (CV _{P + A} ) is an important determinant of our ability to detect biomarker-disease associations. Estimates of CV _I and CV _G may be population specific and little data exists on biomarker variability in diverse Hispanic populations. Hence, we evaluated all 3 components of biomarker variability in the Hispanic Community Health Study/Study of Latinos (HCHS/SOL) using repeat blood collections (n=58) and duplicate blood measurements (n=761-929 depending on the biomarker).
Methods: We estimated the index of individuality (II) ((CV _I +CV _{P + A} )/CV _G ) for 41 analytes and evaluated differences in the II across sexes and age groups.
Results: Biomarkers such as fasting glucose, triglycerides and ferritin had substantially higher inter-individual variability and lower II in HCHS/SOL as compared to the published literature. We also found significant sex-specific differences in the II for neutrophil count, platelet count, hemoglobin, % eosinophils and fasting glucose. The II for fasting insulin, post oral glucose tolerance test glucose and cystatin C was significantly higher among the 18-44y age group as compared to the 45+y age group.
Conclusions: The implications of these findings for determining biomarker-disease associations in Hispanic populations need to be evaluated in future studies.
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