Intra individual variability in markers of proteinuria for normal subjects and those with cadmium induced renal dysfunction: interpretation of results from untimed, random urine samples

This paper reviews the process of elimination of creatinine (CRE), and the limitations presented when using it to express urine concentrations. This literature review leads to three conclusions: (1) CRE excretion is subject to wide fluctuations due to specific internal and external factors; (2) the use of CRE to correct chemical concentrations in urine will not necessarily improve the correlation to the exposure dose for all chemicals (it may, in fact, worsen the result); and (3) other means of expressing urine concentration may offer greater accuracy towards estimating individually absorbed dose. Show more

Most clinical chemical analytes vary in a random manner around a homeostatic set point. Replicate analyses of a series of specimens collected from a group of subjects allows estimation of analytical, within and between subject components of variation. The preferred experimental procedures and statistical methods for evaluation of data and analysis of variance are described; a detailed example is provided in the Appendix. The many uses of data on biological variation in clinical chemistry are reviewed, including setting analytical goals, deciding the significance of changes in serial results from an individual, evaluating the utility of conventional population-based reference values in patient management, and other applications. Show more

The proteinuria rate and the relative clearances of beta 2-microglobulin, orosomucoid, albumin, transferrin and IgG were measured in forty-two workers exposed to cadmium and in seventy-seven control workers. A tubular type proteinuria with an increased excretion of beta 2-microglobulin and often also a glomerular type proteinuria with an increased excretion of orosomucoid, albumin, transferrin and IgG were observed mainly in workers exposed to cadmium for more than 25 years and whose cadmium concentration in blood exceeded 1 microgram Cd/100 ml and that in urine 10 microgram Cd/g creatinine. The glomerular dysfunction was also suggested by an increased plasma level of beta 2-microglobulin and creatinine. Both tubular and glomerular impairments occurred with the same prevalence and were not necessarily associated. The increased release of beta-galactosidase by the kidney suggested that cadmium can damage some epithelial cells. Show more