Understanding eGFR in the clinical context: who does and does not need referral?
1. What care gaps or frequently asked questions have you noticed in the management of low GFR?
We routinely receive questions or referrals about what to do for patients with lower than normal kidney function (eGFR <60 ml/min).
The importance of identifying those with lower than normal kidney function has been made easier since the advent of eGFR reporting. While the equation helps to us to understand serum creatinine as an imprecise measure of kidney function, and draws our attention to abnormal function, it may be that we should be able to understand nuances of kidney function, and avoid referring or labelling those with mild or non progressive disease.
2. Data that answers these questions or gaps:
New data identifies low and high risk individuals within all those with lower eGFR.
There is an increasing awareness, and a set of new equations and studies that state that the eGFR equation is overly sensitive in older patients, particularly older women; and that there needs to be more emphasis placed on proteinuria (as measured by uACR or dipstick), and changes in eGFR over time, before referring patients to specialty services. Studies such as those published by B Hemmelgarn (JAMA 2010), and by the CKD Consortium (Lancet in press) have increased our appreciation that eGFR in individuals over the age of 75 may underestimate true function. Stability of function over time, and lack of proteinuria, or of other abnormalities (such as Hb <115, HCO3 <22, K+ >5.5) are other indicators of the more benign disease, and do not likely require referral.
3. Practice Tip: What we now recommend:
Review eGFR stability over time, measure uACR and other laboratory tests to contextualize findings, before referring, or call nephrologist to determine utility of referral. Reassure patients.
Whilst identifying patients with eGFR < 60 ml/min remains important so as to avoid potential risks like dye and nephrotoxins, it is becoming clear that referring all those with eGFR < 60 ml/min to nephrologists is neither appropriate nor efficient.
Identifying reversible causes (eg. volume depletion, co-administration of drugs like NSAIDs, Coxibs, etc), following patients over time (eg. monthly for 3 months), and contextualizing the kidney function within age issues, other lab parameters, and co-morbidities is equally if not more important. Reassurance of patients about the non progressive nature of their disease is also important.
Referring those cases in which there is ongoing decline or abrupt changes remains important.
In patients with eGFR 45- 60 ml/min who are over the age of 75, there is no need to refer to nephrology unless there is systemic disease, or rapid change in eGFR (such as a fall in kidney function of >25% over 3 month period.
Even in those with eGFR between 30 and 45 ml/min in the absence of abnormal uACR, normal haematology and electrolytes, referral may not add any value to the patients care. Provincial systems to facilitate Rapid Access to Consultant Evaluation (RACE) are being developed, but if there are any questions you can contact a nephrologist for telephone advice for your specific patient.
References: (Note: Article requests require a login ID with the BC College of Physicians website)
Hemmelgarn B, Manns Braden J, Lloyd Anita et al.
Relation between kidney function, proteinuria and adverse outcomes. JAMA 2010; 303(5): 423-29. (View Abstract)
Association of estimated glomerular filtration rate and albuminuria with all-cause and cardiovascular mortality in general population cohorts: a collaborative meta-analysis. Chronic Kidney Disease Prognosis Consortium. The Lancet, Volume 375, Issue 9731, Pages 2073 – 2081, 12 June 2010 (View Article)