proteinuria

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Proteinuria is protein in the urine.

Proteinuria is defined as:

  • albumin:creatinine ratio >30mg/mmol or albumin concentration >200mg/l (1,2) or

  • urine protein:creatinine ratios >45 mg/mmol (2)

The loss of up to 150 mg of protein per day is normal; this may be expressed as normal is less than 4 mg per hour per square metre of body surface area.

Proteinuria may be increased by a factor of 2-3 times by strenuous exercise or fever.

  • other causes of transient include urinary tract infection, vaginal mucus, orthostatic proteinuria (occurs after patient has been upright for some time and is not found in early morning urine - this condition is uncommon in patients over 30 years old) and pregnancy

Causes of persistent proteinuria include:

  • primary renal disease: this may be glomerular (e.g. glomerulonephritis) or tubular
  • secondary renal disease: diabetes mellitus, hypertension, connective tissue diseases, vasculitis, amyloidosis, myeloma, congestive cardiac failure
Pharmacotherapy for CKD (chronic kidney disease) in adults, children, and young people with related persistent proteinuria (2)
  • for adults with CKD and diabetes (type 1 or type 2) offer an ARB (angiotensin receptor blocker) or an ACE inhibitor (titrated to the highest licensed dose that the person can tolerate) if ACR (albumin-creatinine ratio) is 3 mg/mmol or more
  • for children and young people with CKD and diabetes (type 1 or 2), offer an ARB or an ACE inhibitor (titrated to the highest licensed dose that they can tolerate) if ACR is 3 mg/mmol or more
  • for adults with CKD but without diabetes:
    • refer for nephrology assessment and offer an ARB or an ACE inhibitor (titrated to the highest licensed dose that they can tolerate), if ACR is 70 mg/mmol or more
    • if ACR is above 30 but below 70 mg/mmol; consider discussing with a nephrologist if eGFR declines or ACR increases
  • for children and young people with CKD but without diabetes:
    • offer an ARB or an ACE inhibitor if ACR (titrated to the highest licensed dose that they can tolerate) is 70 mg/mol or more
    • if ACR is above 30 but below 70 mg/mmol; consider discussing with a nephrologist if eGFR declines or ACR increase

SGLT2 inhibitors and CKD (2)

  • for adults with CKD and type 2 diabetes, offer an SGLT2 inhibitor, in addition to an ARB or an ACE inhibitor at an optimised dose if:
    • ACR is more than 30 mg/mmol, and
    • they meet the criteria in the marketing authorisation (including relevant eGFR thresholds)
    • monitor for volume depletion and eGFR decline
    • in August 2021, not all SGLT2 inhibitors were licensed for this indication

Notes:

  • NICE suggest that (2):
    • Do not use reagent strips to identify proteinuria in children and young people

    • Do not use reagent strips to identify proteinuria in adults unless they are capable of specifically measuring albumin at low concentrations and expressing the result as an albumin:creatinine ratio (ACR)

    • For the initial detection of proteinuria in adults, children and young people:
      • use urine ACR rather than protein:creatinine ratio (PCR) because of the greater sensitivity for low levels of proteinuria
      • check an ACR between 3 mg/mmol and 70 mg/mmol in a subsequent early morning sample to confirm the result
      • a repeat sample is not needed if the initial ACR is 70 mg/mmol or more

    • Regard a confirmed ACR of 3 mg/mmol or more as clinically important proteinuria

    • Measure proteinuria with urine ACR in the following groups:
      • adults, children and young people with diabetes (type 1 or type 2)
      • adults with an eGFR of less than 60 ml/min/1.73 m2
      • adults with an eGFR of 60 ml/min/1.73 m2 or more if there is a strong suspicion of CKD
      • children and young people without diabetes and with creatinine above the upper limit of the age-appropriate reference range

        When ACR is 70 mg/mmol or more, PCR can be used as an alternative to ACR

    Incidental finding of proteinuria on reagent strips

    • If unexplained proteinuria is an incidental finding on a reagent strip, offer testing for CKD using eGFRcreatinine and ACR
      • ACR (albumin creatinine ratio) category ACR (mg/mmol)
        A1 <3
        A2 3-30*
        A3 >30**

        * Relative to young adult level

        ** Including nephrotic syndrome (ACR usually >220 mg/mmol)

Reference:

Last edited 09/2021 and last reviewed 09/2021

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