Since 2006, we have been reporting renal function in terms of estimated glomerular function (eGFR), using the MDRD (Modification of Diet in Renal Disease study) equation. From 14th November 2023 we will change to the CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) equation as recommended by NICE CKD 2021 guidelines (NG203) as this equation better reflects renal function, especially in younger people without clinical renal disease, and therefore reports fewer false positive results. This change is supported by the renal clinicians within LUHFT, and brings us in to line with the Cheshire & Mersey Pathology Network.
For most patients, the old estimation will be equivalent to the new one. It is important to note the reported creatinine measurement at the same time as the new eGFR. If the creatinine has not changed significantly, then true renal function will not usually have altered and any eGFR change can be attributed to the estimation equation. Likewise, a change in creatinine that is significant could be masked by a seemingly stable eGFR. The change is expected to re-classify CKD stage for some patients. CKD-EPI eGFR still assumes average muscle bulk for patients of that age and gender. Like MDRD, CKD-EPI is not accurate in cachexia or for patients with limb amputations or high muscle bulk.
Key Points:
eGFR values reported from 14/11/23 will have been derived according to the CKD-EPI equation. See NICE NG203 Chronic kidney disease assessment and management.
For most patients, the old estimation will be equivalent to the new one.
CKD-EPI eGFR is expected to classify fewer young people and more older people with chronic kidney disease.
Urine ACR is required for classification and risk stratification of CKD.
If eGFR 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.
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.
Confirm an eGFR result of less than 60 ml/min/1.73 m2 in an adult 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.
This change is supported by the renal physicians within LUHFT, and brings us in to line with the Cheshire & Mersey Pathology Network and NICE NG203.
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