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Background. Estimated albumin excretion rate (eAER) provides a better estimate of 24-h albuminuria than albumin:creatinine ratio (ACR). However, whether eAER is superior to ACR in predicting end-stage renal disease (ESRD), vascular events (VEs) or death is uncertain. Methods. The prognostic utility of ACR and eAER (estimated from ACR, sex, age and race) to predict mortality, ESRD and VEs was compared using Cox proportional hazards regression among 5552 participants with chronic kidney disease in the Study of Heart and Renal Protection, who were not on dialysis at baseline. Results. During a median follow-up of 4.8 years, 1959 participants developed ESRD, 1204 had a VE and 1130 died (641 from a non-vascular, 369 from a vascular and 120 from an unknown cause). After adjustment for age, sex and eGFR, both ACR and eAER were strongly and similarly associated with ESRD risk. The average relative risk (RR) per 10-fold higher level was 2.70 (95% confidence interval 2.45-2.98) for ACR and 2.67 (2.43-2.94) for eAER. Neither ACR nor eAER provided any additional prognostic information for ESRD risk over and above the other. For VEs, there were modest positive associations between both ACR and eAER and risk [adjusted RR per 10-fold higher level 1.37 (1.22-1.53) for ACR and 1.36 (1.22-1.52) for eAER]. Again, neither measure added prognostic information over and above the other. Similar results were observed when ACR and eAER were related to vascular mortality [RR per 10-fold higher level: 1.64 (1.33-2.03) and 1.62 (1.32-2.00), respectively] or to non-vascular mortality [1.53 (1.31-1.79) and 1.50 (1.29-1.76), respectively]. Conclusions. In this study, eAER did not improve risk prediction of ESRD, VEs or mortality. [ABSTRACT FROM AUTHOR]

Background: Exogenous tracer-based methods of measuring glomerular filtration rate (GFR) are difficult to perform, whilst creatinine-based estimation formulae are inaccurate. Methods: We assessed a new technique of measuring iohexol clearance using timed dried capillary blood spots. A reference GFR was measured in 81 subjects (GFR 15–124 ml/min/1.73 m2) by iohexol clearance using three venous samples (2, 3 and 4 h after an intravenous bolus). GFR was estimated by six test methods; iohexol clearance using (i) 3 blood spots (2, 3, 4 h); (ii) 2 blood spots (2, 4 h) and (iii) 1 blood spot (4 h); (iv) the Modification of Diet in Renal Disease (MDRD) formula; (v) the Cockcroft-Gault formula, and (vi) a formula estimating GFR from serum cystatin C concentration. For each test method the bias and precision were calculated as the mean and standard deviation (SD) of the ‘GFR differences’ (test method GFR – reference GFR). Results: The limits of agreement (bias ±1.96 × SD; in ml/min/1.73 m2) were: (i) 1.1 ± 15.1 for 3-spot iohexol clearance; (ii) 0.6 ± 14.9 for 2-spot iohexol clearance; (iii) 4.5 ± 21.2 for 1-spot iohexol clearance; (iv) –15.7 ± 33.3 for the MDRD formula; (v) –9.6 ± 32.9 for the Cockcroft-Gault formula, and (vi) –12.1 ± 31.7 for the Cystatin C formula. The accuracy of all six test methods was similar among individuals with GFR <60 ml/min/ 1.73 m2; however, in individuals with GFR ≥60 ml/min/ 1.73 m2, the MDRD, Cockcroft-Gault and Cystatin C formulae were all imprecise and systematically underestimated GFR. Conclusions: Blood spot iohexol clearance provides a potentially practical method of estimating GFR accurately in large-scale epidemiological studies especially among individuals without established chronic kidney disease. Copyright © 2007 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]