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Blood Sciences Test


Serum – reported with all serum creatinine results including renal function test profiles.

Adults: Calculated result using the CKD-EPI 2009 formula

1 to 18 years: Calculated result using Revised Schwartz Formula (if recent height available on MyCare) as of 25/09/23

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Special Instructions

A variety of methods have been used. All are based on serum creatinine estimations.

Although the Cockcroft-Gault formula is widely used, it was developed to permit estimation of CrCl, not of GFR.

The current recommended equation for 18 years and over is the CKD-EPI formula.

It is important to be aware of the limitations of these equations (more info on eGFR from the UK CKD eGuide):

  • Accuracy – the confidence limits are wide. 90% of values are within 30% of the true value; 98% within 50%.
  • Extremes – none of the methods for estimating GFR without actual measurements of it are likely to be accurate in extreme examples of low muscle mass, or other unusual circumstances.
  • Stability – for all methods, creatinine must not be changing quickly.
  • Systematic errors
  • Age – the Schwartz formula (requires height) should be used in children.

Most UK labs now report eGFR when returning creatinine values. When available, these values should be more accurate than calculations performed by you, as they should incorporate lab-specific correction factors. If not, here are some resources:

The UK Renal Association Website – www.renal.org/eGFR

Online calculator from nephron.com offers a CKD-EPI equation, and has a useful menu of alternatives including US units and also Cockroft-Gault. Take care to set units for creatinine correctly to umol/L (micromol/litre).

We do not use ethnicity adjustment within our CKD-EPI eGFR equation. This is in line with national guidance that these adjustments may not be valid or accurate. See: UKKA for more information.



Reference Range:

see NICE CKD guideline recommendations for interpretation: NICE NG203

Test Usage

Estimation of glomerular filtration rate.

Values above 90 mL/min/1.73 m^2 reported as >90 mL/min/1.73^2

Calculated for patients 18 years or above using CKD-EPI 2009

Calculated for patients 1 to 18 years if height recorded in MyCare within 3 months of sample using revised Schwartz formula



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