New Predictive Equations Improve Monitoring of Kidney Function in Patients With Diabetes

Abstract

OBJECTIVE -The Cockcroft-Gault and Modification of Diet in Renal Disease (MDRD) equations poorly predict glomerular filtration rate (GFR) decline in diabetic patients. We sought to discover whether new equations based on serum creatinine (the Mayo Clinic Quadratic [MCQ] or reexpressed MDRD equations) or four cystatin C-based equations (glomerular filtration rate estimated via cystatin formula [Cys-eGFR]) were less biased and better predicted GFR changes.RESEARCH DESIGN AND METHODS -In 124 diabetic patients with a large range of isotopic GFR (iGFR) (56.1 Ϯ 35.3 ml/min per 1.73 m 2 [range 5-164]), we compared the performances of the equations before and after categorization in GFR tertiles. A total of 20 patients had a second determination 2 years later.RESULTS -The Cockcroft-Gault equation was the least precise. The MDRD equation was the most precise but the most biased according to the Bland-Altman procedure. By contrast with the MDRD and, to a lesser extent, the MCQ, three of the four Cys-eGFRs were not biased. All equations overestimated the low GFRs, whereas only the MDRD and Rule's Cys-eGFR equations underestimated the high GFRs. For the subjects studied twice, iGFR changed by Ϫ8.5 Ϯ 17.9 ml/min per 1.73 m 2 . GFR changes estimated by the Cockcroft-Gault (Ϫ4.5 Ϯ 6.8) and MDRD (Ϫ5.7 Ϯ 6.2) equations did not correlate with the isotopic changes, whereas new equationpredicted changes did: MCQ: Ϫ8.7 Ϯ 9.4 (r ϭ 0.44, P Ͻ 0.05) and all four Cys-eGFRs: Ϫ6.2 Ϯ 7.4 to Ϫ7.3 Ϯ 8.4 (r ϭ 0.60 to 0.62, all P Ͻ 0.005), such as 100/cystatin-C (r ϭ 0.61, P Ͻ 0.005). CONCLUSIONS -The new predictive equations better estimate GFR than the CockcroftGault equation. Although the MDRD equation remains the most accurate, it poorly predicts GFR decline, as it overestimates low and underestimates high GFRs. This bias is lesser with the MCQ and Cys-eGFR equations, so they better predict GFR changes. 30:1988-1994, 2007 C hronic kidney disease (CKD) is a major health problem worldwide, with dramatically rising incidence and prevalence. Patients with diabetes are particularly affected by this negative development. It is necessary to stratify CKD and estimate its progression because diabetes is the leading cause of end-stage renal disease (1). The National Kidney Foundation guidelines recommend estimating glomerular filtration rate (GFR) in subjects with CKD (2). According to the National Kidney Foundation and the American Diabetes Association, GFR can be estimated in adults by using the Cockcroft-Gault or the Modification of Diet in Renal Disease (MDRD) equations (1,3). Neither of these equations, based on serum creatinine, is highly predictive of GFR. The Cockcroft-Gault equation is less accurate (4), biased by body weight (5), and less robust in patients with poor glycemic control (6). The simplified MDRD equation allows renal function to be classified with acceptable precision and requires only usual information about the patient. However, adjustment may be required to avoid error due to creatinine assays and calibrators (7). Moreov...

Cystatin C: current position and future prospects

“…Since then we have seen a real ''epidemic'' of equations based on CysC (21,(110)(111)(112)(113)(114)(115), particularly as simultaneously with the discovery of extra renal effects on serum cystatin, some authors have logically developed different equations depending on patient type or equations expressing a corrective factor based on age, sex or disease (115)(116)(117) (Table 4). Some authors have also recently advanced the hypothesis that an equation combining creatinine and CysC may be useful (111, 115-117, 125, 126).…”

“…Others are complex as they use additional non-biological parameters which do not provide any apparent advantage. In general, it can also be stated that these equations have been subject to very limited validation in populations other than those in which they were constructed (110)(111)(112)(113)(114)(115). At present, these equations appear to offer very limited advantage compared to the MDRD equation, which is based on serum creatinine, age, sex and race, at least for the general population (110-115, 127, 128).…”

Značaj cistatina C kao faktora rizika za kardiovaskularne bolesti kod oboljelih od tipa 2 diabetes mellitus-a

“…Primjena cistatina C pokazala se pouzdanom u procjeni početnog oštećenja bubrežne funkcije kada su vrijednosti kreatinina još uvijek u okviru referentnih, odnosno u području "slijepog opsega" kreatinina [5]. Primjenom različitih formula moguće je izračunati vrijednosti GFR iz serumskog cistatina C [6,7]. Utvrđeno je da smanjenje GFR predstavlja nezavisan faktor rizika za buduće kardiovaskularne događaje i mortalitet, čak i u slučajevima kada postoji blagi pad GFR.…”

Evaluation de la fonction rénale chez les patients atteints de maladie cardio vasculaire (MCV) : comparaison entre la créatinine et la cystatine C

“…Pour ce qui est des formules basées sur la cystatinémie C, leur avantage apparaît, au jour d'aujourd'hui, relativement faible par rapport aux formules MDRD et CKD-EPI basées sur la créatininémie, l'âge, le sexe et la race, en ce qui concerne la population générale (Beauvieux et al, 2007;Herget-Rosenthal et al, 2007) et leur précision semble aussi limitée (Beauvieux et al, 2007 ;Zahran et al, 2007). Devant cet état de fait, certains auteurs recommandent des formules combinant la créatinine et la cystatine C (Ma et al, 2007;Stevens et al, 2008).…”