Urine albumin creatinine ratio (UAR) versus urine protein creatinine ratio (PCR)

Proteinuria is important diagnostic test and a bad prognostic marker for Chronic Kidney Diseases (CKD) with or without diabetes mellitus and cardiovascular diseases.

• total proteinuria consists of albuminuria from glomeruli, filtered immunoglobulins as well as tubular proteins like Tamm Harsfall protein. Detection and quantification of urinary albumin is vital for diagnosis and management of most renal disorders
  
  
• urinary total protein is <150mg/day. Normal Albumin excretion is <20mg/day
  
  
• proteinuria is defined as: albumin:creatinine ratio >30mg/mmol or albumin concentration >200mg/l or urine protein:creatinine ratios >45 mg/mmol
  
  
• there is moderate to high correlation between spot urine protein creatinine ratio (PCR) and 24 hour urinary protein excretion. Urinary albumin concentration correlates well with urinary total protein and also with 24 hour urinary protein over a very wide range of the level of proteinuria
  
  
• in persons with CKD, ACR and PCR were shown to be relatively comparable in their associations with common complications of CKD (2)
  

Notes:

• albumin is a low molecular weight protein, and albuminuria is likely a reflection of early damage to the glomerular vascular endothelium as well as decreased ability of the tubule to reabsorb urinary albumin
  • urinary measurement of total proteinuria includes higher molecular weight non-albumin urinary proteins as well, which may be tubular as well as glomerular in origin
  • however albumin still comprises the majority of total urinary protein in patients with CKD (particularly at higher ranges of proteinuria)
    • therefore it seems logical that these two clinical measures would be comparable in the general CKD population
      

Reference:

• Pandya B, Hayden K. Albumin Creatinine Ratio (ACR) versus Protein Creatinine Ratio (PCR) for Nephrology Referral criteria in Primary Care.
• Fisher H et al. Comparison of associations of urine protein-creatinine ratio versus albumin-creatinine ratio with complications of CKD: a cross-sectional analysis.Am J Kidney Dis. 2013 Dec;62(6):1102-8.