Effects of transportation and delay in processing on the stability of nutritional and metabolic biomarkers

The effects of transportation and delay in processing of blood samples on t he concentration of biomarkers are significant in epidemiological studies f or which specimens are collected from participants at locations other than a designated center or laboratory. These sources of variability in measurem ent were studied by collecting two sets of blood samples from 51 men betwee n 26 and 50 years of age. The first set was sent immediately to the laborat ory or processing. The second set was transported by car for one hour and t hen returned to the laboratory for processing. Both sets were stored togeth er at -80 degreesC until the end of the study. Several blood constituents w ere evaluated. Vitamins, liver enzymes, and electrolytes showed no changes in concentration after transport by car for one hour. There were decreases in the concentrations of red and white blood cells, high-density-lipoprotei n cholesterol, glucose, and creatinine after transportation. The transporte d total cholesterol, total testosterone, free testosterone, alkaline phosph atase, total bilirubin, and thiobarbituric acid-reactive substances increas ed in concentration. Although transportation and delay in processing of blo od samples do not appear to greatly impact relative risk estimates, epidemi ologists should be aware of these potential sources of variability in measu rement and consider the consequences in their particular study.