Recent Developments in the Evaluation of Glomerular Filtration Rate: Is There a Place for [Beta]-Trace?(Editorials‪)‬

The National Kidney Foundations "K/DOQI clinical practice guidelines for chronic kidney disease" and the recent European recommendations now provide consensus guidelines on the use of laboratory methods in estimating and measuring glomerular filtration rate (GFR) (1, 2). Professionals in clinical chemistry will need to be well acquainted with these 2 guidelines because the clinical chemistry laboratory is concerned in several ways. As a sum of the filtration rate of all functioning nephrons, GFR represents the best overall index of the extent of renal function (1). GFR can be measured only indirectly. The determination should use an ideal filtration marker that, after having reached a stable plasma concentration, is physiologically inert; is freely filtered in the glomerulus; is not secreted, metabolized, synthesized, or reabsorbed in the tubulus; is not extrarenally eliminated; is stable; and is easily measurable. A gold standard measure of GFR uses inulin as a filtration marker. Other exogenously administered substances (e.g., [sup.125]I-iothalamate, [sup.99m]Tc-diethylenetriaminepentaacetic acid, [sup.15]Cr-EDTA, and iohexol) can also provide a surrogate measure of GFR. Because these methods are labor-intensive, costly, and cumbersome for patients and staff, they are predominantly used in research settings and make up only a very small proportion of renal function determinations in routine clinical settings.