ARE FROZEN URINE SAMPLES ACCEPTABLE FOR ESTIMATING ALBUMIN EXCRETION IN RESEARCH

Timed urine collections from diabetic children and adolescents were as sessed for urinary albumin excretion rate (mu g min(-1)) before and af ter freezing at -20 degrees C. Freezing had the effect of changing the estimation such that frozen values could differ from that of the fres h, by as much as one half to twice as much. The variation depended on the concentration defining the initial albumin excretion rate but was not influenced by the length of storage when frozen. We conclude that researchers should be aware that freezing and storing of urine samples prior to albumin concentration assessments can affect the absolute va lues obtained. It would appear more appropriate to analyse samples pri or to freezing to be certain of obtaining true prevalence estimates of microalbuminuria.