Explaining eGFR and the Risk Equation
Our new online referral pathway tool for primary-care providers helps you determine the best course of action for your patient and know when a referral to the Manitoba Renal Program is necessary. Here is some additional info to better understand the pathways and eGFR based risk prediction.
- Automatic estimated Glomerular Filtration Rate (eGFR) reporting was introduced in Manitoba in 2010 per Canadian Society of Nephrology guidelines to assist practitioners in the early identification of chronic kidney disease (CKD).
- eGFR <30 ml/min adequately predicts increased patient risk for End-Stage Renal Disease (ESRD). However, it is recognized that in patients with milder degrees of CKD, with eGFR. >30 ml/min, it alone is often insufficient to predict the risk of progression to ESRD.
- Recommendations from the Kidney Dialysis Improving Global Outcomes (KDIGO) group in 2012 endorse predicting CKD progression risk to guide decisions for testing and treatment of CKD complications.
- – eGFR < 60 ml/min/1.73m2
eGFR derived by the CKD-EPI equation has become the standard to assess kidney function in most adult outpatients with stable CKD. eGFR outperforms 24 hour urine collection and/or measured GFR in diagnosis and prognostication.
Manitoba Renal Program Recommendations:
- If eGFR is reported as < 60 ml/min/1.73m2, it should be repeated to ensure it is not declining rapidly, and again after three months to determine if persistent, or chronic. This should also be accompanied by a urinalysis and estimation of protein excretion rate to calculate each individual’s risk of CKD progression.
- Patients are deemed to have CKD if there are abnormalities of kidney imaging, urinalysis or function (eGFR < 60 ml/min/1.73m2) for greater than three months.
- Routine urinalysis and an estimate of protein excretion rate should be done to help guide diagnosis, management and predict risk of progression of CKD.
- eGFR only provides information about the degree but not the cause of kidney impairment; further assessment of urinary sediment, protein excretion rate and imaging is required. Determining whether a patient has CKD should not be based on eGFR in isolation.
- eGFR should be used with caution in the very elderly, and those with extreme body composition (i.e. amputations, very obese or lean) and pregnancy. eGFR may under or overestimate the true GFR with any of these variables.
- eGFR requires a correction/conjugation for African American ethnicity. In these patients, eGFR should be multiplied by 1.21.
- Drugs that inhibit the tubular secretion of creatinine (i.e. trimethoprim, fibric acid derivatives other than gemfibrozil) can affect the accuracy of eGFR
- eGFR should not be used in patients with acute kidney injury.
- Nephrology referral should be considered for eGFR < 60/ml/min or/and proteinuria per criteria outlined in the MRP Kidney Disease Referral Pathway.
Kidney Failure Risk Equation
- The Manitoba Renal Program now uses a calculator to better identify patients at increased risk for progression to End-Stage Renal Disease, especially in those with eGFRs from 30-60 ml/min. This calculator requires the following information:
- Age and sex
- Creatinine/estimated GFR (eGFR) – preferably two values
- Urine albumin: creatinine ratio
- When the MRP triages patients for timely nephrology consultation, we require that you provide the above information, in addition to your patient’s past medical history, medications list and urinalysis, which aid the triaging process and to appropriately risk stratify each patient.
- Using the risk prediction calculator, we define a patient’s overall risk for developing End-Stage Renal Disease over five years. Those at intermediate or high risk are identified and assessed accordingly. Those that have a <3% predicted risk of developing ESRD over five years are felt to be low risk and as a result, nephrology referral may currently not be indicated.
- This can be illustrated by the following example:
- Two female patients 75 years old each with eGFR of 45 ml/min and a history of hypertension. A urine ACR for patient A is 10 mg/mmol and patient B is 100 mg/mmol. Patient A is found to be at 1.9% and patient B at 4.2% risk of progression to ESRD in five years.
- Therefore, the consult on patient A would be returned as low risk with appropriate guidelines and patient B would be booked for routine assessment by nephrology.
Do not hesitate to contact us with questions at any time.
* Tangri N, Stevens LA, Griffith J, et al. A predictive model for progression of chronic kidney disease to kidney failure. JAMA. 2011;305(15). DOI:10.001/jama.2011.451