9 Unfortunately, the measurement of UPC cannot be standardized because urine protein is composed of variable proportions of albumin and other proteins.18 Dip-stick proteinuria correlates poorly with ACR,22,23 while PCR correlates reasonably well with ACR.24 Proteinuria of 0.5 g/day or more usually signifies macroalbuminuria.1,4 However, there have been no studies on the direct comparison between proteinuria and albuminuria in CKD in terms of utilities (biomarker, surrogate end-point and cost-effectiveness). Thus, any comparison between proteinuria and albuminuria in CKD is subject to problems inherent in indirect comparisons.25 Proteinuria and
albuminuria are good biomarkers (Table 1) because they predict clinical end-points (CV events, renal events or mortality) Hydroxychloroquine in both diabetic and non-diabetic patients.2,3 However, there must be three general lines of evidence to support the acceptance of a biomarker to be a surrogate end-point: biological plausibility, epidemiological data and RCT.3 Despite ample evidence in biological plausibility and epidemiological data, there are limitations in RCT regarding the validity of proteinuria or albuminuria as a surrogate end-point.3 For example, a secondary analysis (but not a primary analysis) of
the Modification of Diet in Renal Disease (MDRD) study indicated that a low BP target slows the GFR decline only in patients with proteinuria of 3 g/day or more.26 Similarly, a secondary analysis of the Prevention Palbociclib molecular weight of Renal and Vascular End-stage Disease Intervention Trial (PREVEND-IT) found that BP lowering decreases CV events only
in patients with higher albuminuria levels.27 The Ongoing Telmisartan Alone and in Combination with Ramipril Global End-point Trial (ONTARGET) study even found that combined ACEI and ARB therapies decrease ACR while increasing renal outcome.3 Moreover, there has only been one renoprotective RCT with proteinuria as a treatment target to show that a reduction in proteinuria by titrated ACEI decreases Cediranib (AZD2171) renal end-points.28 Unfortunately, there have been no RCT with head-to-head comparisons between proteinuria and albuminuria.2 However, a change between normoalbuminuria and macroalbuminuria may be a surrogate for the development or remission of early diabetic nephropathy (Table 1).3 The remission of nephrotic proteinuria is a surrogate for the remission of GFR decline (Table 1).3 Moreover, ACEI- or ARB-induced change in proteinuria or albuminuria is a surrogate for changes in CKD progression in patients with mild to moderate proteinuria (Table 1).3 A randomized trial comparing screening for proteinuria and albuminuria is the best evidence of cost-effectiveness, but modelling is an alternative.29 However, most modelling approaches estimate effectiveness from traditional RCT, which are designed for testing efficacy and are not suitable for cost-effectiveness studies.