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 18–44 y 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.