AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |
Back to Blog
Egfr range1/21/2024 ![]() ![]() ![]() The overall average decline in Ccr was −0.75ml/min/year. time (or age) (in ml/min/year) became negative after age 39, and the rate of decline in Ccr slowly accelerated to reach a peak value of minus 3.25 ml/min/year after age 80 years (See Table I). In a later study (including many of the subjects studied by Rowe et al), conducted by Lindeman, Tobin and Shock ( 11) and reported in 1985, the Ccr was examined in 254 apparently “normal” men (some of whom had diabetes mellitus unaccompanied by proteinuria). Importantly, the decline in Ccr was independent of blood pressure values and other co-morbid conditions affecting the elderly. In longitudinal studies involving three or more Ccr measurements carried out over 12–18 months in 293 “normal” subjects, a similar pattern of decline of Ccr with age was again observed, with an acceleration in the rate of decline with advancing age. Among 548 normal subjects studied by Rowe et al ( 10) in 1976, the Ccr fell from 140 ml/min/1.73m2 at age 30 years to about 97 ml/min/1.73m2 at age 80 years. In a series of reports from this group, in conjunction with the Baltimore Longitudinal Study of Aging and using both cross-sectional and longitudinal study design, the changes in Ccr consequent to ageing were examined in community-living, apparently “normal” men, 20–89 years of age. Later studies carried out by Rowe et al ( 10) and Lindeman, Tobin and Shock ( 11) utilized Ccr as an approximate measure of GFR. The filtration fraction (GFR divided by Renal Plasma Flow or RPF) tended to remain constant until about age 65 years and older ( 7). In the original studies of Davies and Shock the average decline in GFR was 0.96 ml/min/year or about 10 ml/min/decade ( 7). Most of these studies have been cross-sectional and have rather uniformly shown that the GFR declines steadily with aging, beginning at age 30–40 years, with an apparent acceleration in the rate of decline after age 65–70 years ( 6– 9). Many reports of the measurements of Cin or Ccr in aging subjects have appeared since the pioneering studies of Nathan Shock and his colleagues beginning in 1945 ( 6, 7). The Ccr overestimates the Cin by about 22% due to the fact that creatinine is normally secreted by the renal tubule. One of these is the clearance of endogenous creatinine (Ccr), a substance produced in muscle by the non-enzymatic dehydration of creatine. Since then numerous methods have been devised for assessment of GFR which approximate the Cin. The constant infusion of Inulin along with timed urine collection and plasma sampling with calculation of the Inulin Clearance (Cin) is now the “gold standard” for measurement of GFR. Measurement of the rate of formation of the glomerular filtrate (GFR) did not achieve reality until 1926 ( 2, 3) and real precision was obtained as a result of the pioneering studies of A.N Richards ( 4) and Homer Smith ( 5) in 1934–1935, investigators who independently described the use of Inulin (a polysaccharide neither secreted nor reabsorbed by the renal tubules and which is freely filtered at the glomerulus) as a substance to measure GFR using the clearance method. The process of glomerular filtration has been recognized for over 160 years, since Ludwig in 1844 first proposed the physico-mechanical formation of a protein-free ultrafiltrate by the renal glomeruli ( 1). This paper discusses the known effects of ageing on GFR and the consequences of using a classification system for defining CKD that does not take into account the normal decline of GFR with ageing. ![]() A consequence of these criteria has been to overstate the frequency of CKD in the general population and to generate many “false positive” diagnoses of CKD. These criteria for diagnosis of CKD include an absolute threshold for eGFR, unadjusted for the effects of age on the normal values for eGFR. In the last decade a new paradigm has been introduced in which the true or measured GFR is estimated (eGFR) by formulas based on serum creatinine levels and in which these estimates are applied to the diagnoses of chronic kidney disease (CKD) in the general population. This decline appears to be a part of the normal physiologic process of cellular and organ senescence and is associated with structural changes in the kidneys. The rate of decline may accelerate after age 50–60 years. Studies conducted in the 1930's to the 1950's clearly established that GFR declines, perhaps inexorably, with normal ageing, usually beginning after 30–40 years of age. The process of glomerular filtration of plasma fluid has been known for over 160 years and the measurement of the rate of its formation (glomerular filtration rate, GFR) has been possible for over 80 years. ![]()
0 Comments
Read More
Leave a Reply. |