Monitoring of chronic kidney disease (CKD)

NICE suggest (1):

• clinicians should use urine albumin:creatinine ratio (ACR) in preference to protein:creatinine ration (PCR) in order to detect proteinuria
  • ACR has greater sensitivity than protein:creatinine ratio (PCR) for low levels of proteinuria. For quantification and monitoring of proteinuria, PCR can be used as an alternative. ACR is the recommended method for people with diabetes
• for the initial detection of proteinuria, if the ACR is between 3 mg/mmol and 70 mg/mmol, this should be confirmed by a subsequent early morning sample. If the initial ACR is 70 mg/mmol or more, a repeat sample need not be tested
• regard a confirmed ACR of 3 mg/mmol or more as clinically important proteinuria Quantify urinary albumin or urinary protein loss as in recommendation
  • all people with diabetes, and people without diabetes with a GFR less than 60 ml/min/1.73 m^2, should have their urinary albumin/protein excretion quantified. The first abnormal result should be confirmed on an early morning sample (if not previously obtained)
  • quantify by laboratory testing the urinary albumin/protein excretion of people with an eGFR 60 ml/min/1.73 m^2 or more if there is a strong suspicion of CKD
    
    
• frequency of monitoring - Frequency of monitoring of GFR (number of times per year, by GFR and ACR category) for people with, or at risk of, CKD

• where a highly accurate measure of GFR is required - for example, during monitoring of chemotherapy and in the evaluation of renal function in potential living donors - consider a gold standard measure (inulin, 51Cr-EDTA, 125I-iothalamate or iohexol)

• Defining progression
  • define accelerated progression of CKD as:
    • a sustained decrease in GFR of 25% or more and a change in GFR category within 12 months
    • or a sustained decrease in GFR of 15 ml/min/1.73 m2 per year
      
      
  • take the following steps to identify the rate of progression of CKD:
    • obtain a minimum of 3 GFR estimations over a period of not less than 90 days
    • in people with a new finding of reduced GFR, repeat the GFR within 2 weeks to exclude causes of acute deterioration of GFR- for example, acute kidney injury or starting renin-angiotensin system antagonist therapy
      
      
  • be aware that people with CKD are at increased risk of progression to endstage kidney disease if they have either of the following:
    • a sustained decrease in GFR of 25% or more over 12 months or
    • a sustained decrease in GFR of 15 ml/min/1.73 m^2 or more over 12 months
      
      
• NICE previously defined progressive CKD as a decline in eGFR of > 5 mL/min/1.73 m2 in one year (or 10 mL/min/1.73 m^2 in five years) (3)
  
  
• Referral criteria
  • people with CKD in the following groups should normally be referred for specialist assessment:
    
    
    • GFR less than 30 ml/min/1.73 m2 (GFR category G4 or G5), with or without diabetes
      
      
    • ACR 70 mg/mmol or more, unless known to be caused by diabetes and already appropriately treated
      
      
    • ACR 30 mg/mmol or more (ACR category A3), together with haematuria
      
      
    • sustained decrease in GFR of 25% or more, and a change in GFR category or sustained decrease in GFR of 15 ml/min/1.73 m2 or more within 12 months
      
      
    • hypertension that remains poorly controlled despite the use of at least 4 antihypertensive drugs at therapeutic doses
      
      
    • known or suspected rare or genetic causes of CKD
      
      
    • suspected renal artery stenosis
      
      
• also (3):
  • 1) to seek clarification when diagnostic uncertainty exists, ie to identify people whose renal disease exhibits features that are not in keeping with CKD due to systemic vascular disease and who may need specialist evaluation and intervention
    • important that GPs are familiar with the expected clinical features of CKD and can identify features that suggest a patient's renal impairment may be due to something other than systemic vascular disease (and may possibly have a remediable cause)
      • useful diagnostic clues include:
      • patients with CKD due to systemic vascular disease must have a defined risk factor, such as hypertension or diabetes, and failure to identify one raises the possibility of primary renal disease
      • heavy proteinuria (ACR > 70 mg/mmol, PCR > 100 mg/mmol is not typical of CKD. These patients may have a primary renal disease
      • haematuria (seen or unseen) rarely accompanies CKD caused by systemic vascular disease. This finding should prompt referral according to local guidelines
      • decline in renal function in CKD is slow. As outlined above, NICE has defined a rate of fall in eGFR above which referral is advised
        • in patients whose rate of decline is accelerated by ACE inhibitors, the possibility of renovascular disease is raised
  • 2) to give patients known to have CKD timely access to specialist services not available in primary care, such as pre-dialysis work-up, anaemia management etc.

Reference:

• (1) NICE (August 2021). Chronic kidney disease: assessment and management
• (2) PCCJ - Volume 2, Special Issue 1, April-May-June 2009
• (3) NICE (September 2008). Chronic Kidney Disease - Early identification and management of chronic kidney disease in adults in primary and secondary care