The repeatability of serum carotenoid, retinoid, and tocopherol concentrations in specimens of blood collected 15 years apart

Community-wide programs to collect blood for a research serum bank were car ried out in Washington County, Maryland in 1974 and 1989. Of the 8395 perso ns who participated in both programs, 64 were controls in a nested case-con trol study of the association of antioxidant micronutrients with subsequent breast cancer, and 30 and 166 were controls in similar studies of lung and prostate cancer. Assay results for five carotenoids, two retinoids, and tw o tocopherols in samples of blood collected 15 years apart were thus availa ble for comparisons of micronutrient concentrations. The mean Spearman rank order correlation coefficient for all comparisons was 0.44, with two coeff icients greater than 0.60 and two less than 0,30, Blood pressure readings a t the two blood collections had a mean rank order correlation coefficient o f 0.46, Because blood pressure readings in 1974 were shown to be significan tly predictive of atherosclerosis 15-18 years later, the present results su ggest that ranked concentrations of antioxidant micronutrients from a singl e sample are sufficiently representative to be used as predictors of subseq uent concentrations and are thus suitable for assessment as risk factors fo r subsequent illnesses.