136 - Albuminuria: the Laboratory contribution
Autor(s): M.S. Graziani, A. Caldini
Issue: RIMeL - IJLaM, Vol. 3, N. 3-S1, 2007 (MAF Servizi srl ed.)
Page(s): 136-141
Urine albumin is a sensitive marker of renal derangement; accordingly with the current guidelines, the measurement is required for an appropriate monitoring of diabetic patients annually. In spite of its clinical importance the standardisation of the laboratory measurement is lacking. The presentation is twofold: to illustrate the results of an Italian survey on the state of the art of the laboratory measurement and to examine the main problems the Clinical Laboratory should face in the next future in order to give the correct answer to clinical needs. The survey results show that there is a need for improvement of the albumin measurement analytical quality and that it is of even more importance the standardization of the post analytical phase (reporting and interpreting the results). Recent studies have demonstrated that the nature of albumin in urine is more complex than previously thought. Albumin can be excreted as intact molecule or degradated as fragments of different molecular weights; furthermore the intact molecule can be immunoreactive or not due to chemical modifications of the molecule. Methods based on different principles are able to detect different forms of albumin and give thus different results. Current microalbuminuria assays use different kinds of immunochemical methods. These methods may lead to underestimation of albumin in urine samples containing non immunoreactive albumin. To overcome this problem, different methodologies have been proposed. Before the results of these new techniques could be validated for clinical utilization, it should be demonstrated that the new measurements lead to effective improvement in clinical outcomes. Analytical quality specifications, and in particular sensitivity, are another critical issue. There is increasing evidence that a continuous relationship between albumin excretion and risk exists so that non lower bound between normal and increased albuminuria can be identified that segregates subjects at different risk. The sensitivity of the laboratory method is, in this context, crucial. A more strict adhesion of Italian Laboratories to the existing guidelines should be encouraged. At the same time the standardisation of the test, including an accurate definition of the analyte, is mandatory in the next future.