About eGFR

The following eGFR calculator is recommended to determine stages of chronic Kidney Disease (CKD). 
http://mdrd.com/

The latest NICE guidance on measurement of kidney function are detailed below www.nice.org.uk/guidance/cg182

 Please note:

  • Cystatin C measurement is not widely available
  • NICE recommendation is for use of the CKD –EPI calculator for estimation of eGFR
  • eGFR calculations are NOT valid in the setting of pregnancy & extremes of body mass or under 18y age
  • Do not diagnose CKD if GFR is 60-90 ml/min/1.73m2 without other features of CKD

 Classification of CKD is defined below www.nice.org.uk/guidance/cg182

 

GFR

 

1.1 Investigations for chronic kidney disease

Measuring kidney function

Creatinine-based estimate of GFR

1.1.1 Whenever a request for serum creatinine measurement is made, clinical laboratories should report an estimate of glomerular filtration rate (eGFRcreatinine) using a prediction equation (see recommendation 1.1.2) in addition to reporting the serum creatinine result[2]. [2014]

1.1.2 Clinical laboratories should:

  • use the Chronic Kidney Disease Epidemiology Collaboration (CKD‑EPI) creatinine equation to estimate GFRcreatinine, using creatinine assays with calibration traceable to standardised reference material
  • use creatinine assays that are specific (for example, enzymatic assays) and zero-biased compared with isotope dilution mass spectrometry (IDMS)
  • participate in a UK national external quality assessment scheme for creatinine. [new 2014] For more information about implementing this recommendation, see implementation: getting started.

1.1.3 Apply a correction factor to GFR values estimated using the CKD‑EPI creatinine equation for people of African-Caribbean or African family origin (multiply eGFR by 1.159). [new 2014]

1.1.4 In people with extremes of muscle mass – for example, in bodybuilders, people who have had an amputation or people with muscle wasting disorders – interpret eGFRcreatinine with caution. (Reduced muscle mass will lead to overestimation and increased muscle mass to underestimation of the GFR.) [2008]

1.1.5 Advise people not to eat any meat in the 12 hours before having a blood test for eGFRcreatinine. Avoid delaying the despatch of blood samples to ensure that they are received and processed by the laboratory within 12 hours of venepuncture. [2008]

Cystatin C-based estimate of GFR

1.1.6 Whenever a request for serum cystatin C measurement is made, clinical laboratories should report an estimate of glomerular filtration rate (eGFRcystatinC) using a prediction equation (see recommendation 1.1.7) in addition to reporting the serum cystatin C result. [new 2014]

1.1.7 When an improved assessment of risk is needed (see recommendation 1.1.14), clinical laboratories should use the CKD‑EPI cystatin C equation to estimate GFRcystatinC. [new 2014]

1.1.8 Clinical laboratories should use cystatin C assays calibrated to the international standard to measure serum cystatin C for cystatin C-based estimates of GFR. [new 2014]

1.1.9 Interpret eGFRcystatinC with caution in people with uncontrolled thyroid disease because eGFRcystatinC values may be falsely elevated in people with hypothyroidism and reduced in people with hyperthyroidism. [new 2014]

Reporting and interpreting GFR values

1.1.10 Clinical laboratories should report GFR either as a whole number if it is 90 ml/min/1.73 m2 or less, or as 'greater than 90 ml/min/1.73 m2'. [new 2014]

1.1.11 If GFR is greater than 90 ml/min/1.73 m2, use an increase in serum creatinine concentration of more than 20% to infer significant reduction in kidney function. [new 2014]

1.1.12 Interpret eGFR values of 60 ml/min/1.73 m2 or more with caution, bearing in mind that estimates of GFR become less accurate as the true GFR increases. [2014]

1.1.13 Confirm an eGFR result of less than 60 ml/min/1.73 m2 in a person not previously tested by repeating the test within 2 weeks. Allow for biological and analytical variability of serum creatinine (±5%) when interpreting changes in eGFR. [2008]

When to use a cystatin C-based estimate of GFR for diagnosis of CKD

1.1.14 Consider using eGFRcystatinC at initial diagnosis to confirm or rule out CKD in people with:

  • an eGFRcreatinine of 45–59 ml/min/1.73 m2, sustained for at least 90 days and
  • ·no proteinuria (albumin:creatinine ratio [ACR] less than 3 mg/mmol) or other marker of kidney disease. [new 2014] For information about implementing this recommendation, see implementation: getting started.

1.1.15 Do not diagnose CKD in people with:

  • an eGFRcreatinine of 45–59 ml/min/1.73 m2 and
  • an eGFRcystatinC of more than 60 ml/min/1.73 m2 and
  • ·no other marker of kidney disease. [new 2014]

When highly accurate measures of GFR are required

1.1.16 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 reference standard measure (inulin, 51Cr‑EDTA, 125I‑iothalamate or iohexol). [2008]

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