Time to differentiate 'function' from 'disease'.
Let’s not confuse ‘function’ with ‘disease’. Kidney function (KF) is
similar to left ventricular function (LVEF) – a number with prognostic
implications irrespective of the underling disease process. As some
healthy persons may have Grade 2 LV function without heart disease,
similarly many healthy elderly persons may have stage 3 kidney function
(KF) without kidney disease. In both circumstances, there may be increased
risk of cardiovascular mortality (as shown in various epidemiological
studies – although these studies suggested increased CV risk with stage 3
CKD but none clearly established that all patients with decreased
estimated glomerular filtration rate (eGFR) really had kidney disease, my
understanding is, that it is stage 3 KF rather than 'true' stage 3 CKD)
and we should all recognize this without undermining the importance of
The estimated eGFR gives a number that in this circumstance describes
nothing else than the ‘kidney function.’ It is important to recognize that
decreased function doesn’t mean disease and disease doesn't mean decreased
kidney function. I can understand the confusion created by the current
guidelines among the promary care providers and non-nephrologists, when
there is not a consensus among nephrologists and concerns about the
current guidelines are being published rapidly.
The so called ‘epidemic of CKD’ is created by ballooning of stage 3,
where many healthy elderly persons with low normal eGFR have been
classified as having a disease and undergoing unnecessary investigations,
nephrology consultations and wasting resources. I fully agree with
division of stage 3 kidney function into 2 stages – stage 3A and stage 3B,
as proposed by NICE.
“Kidney disease” and “Kidney function” are separate and doesn’t
always correlate, although majority of persons with decreased kidney
function – stage 3b, 4 and 5 have kidney disease.
I believe that current staging based on eGFR [understanding that it
only defines a function] is reasonable but requires modification and
should consider classifying as stages of kidney function (KF) than stages
of disease (CKD), as patients with normal function may have disease and
similarly person with decreased eGFR may not have the disease. I agree
with Bauer et al that reporting eGFR with all serum creatinine levels
is valuable in recognizing reduced kidney function, irrespective of
whether the individual has kidney disease or not, that would improve drug
dosing and reduce nephrotoxin exposure in such individuals.
The kidney disease should be labeled as an individual diagnosis and
the term ‘CKD’ should be reserved for persons with ill-defined kidney
disease. A patient with IgA nephritis with eGFR of 55 ml/min/1.73 m2
should be classified as, “IgA nephritis stage 3 KF” than “IgA nephritis
stage 3 CKD”. An elderly person with no underlying kidney disease may then
be classified as, “no evidence of kidney disease, stage 3 KF” or “ Stage 3
KF, possibly age-related” and a person with chronically scarred kidneys
with eGFR of 55 ml/min/1.73 m2 may then be classified as, “CKD, stage 3
KF”. Lumping together several diseases into a single large group “CKD”
based on eGFR potentially may results in failure of diagnosis in some
The recommendation that all patients with diabetic kidney disease
should undergo albumin:creatinine ratio (ACR) monitoring is NOT CORRECT
and would cause MORE confusion among the practitioners as one has already
alluded to in the rapid responses. If this recommendation is not modified,
wait when nephrologists are going to be flooded with calls about ACR of
1000 or higher on emergent basis, especially in patients with known overt
nephropathy and nephrotic range proteinuria.
ACR is a screening test and should be used for screening purposes,
when patients have low grade proteinuria or albuminuria, however, once
urine protein excretion is over 0.5g/d, the urine dipstick is often
positive for protein and when the urine dipstick is persistently positive
for protein, then use of urine protein:creatinine ratio (UPR) is
reasonable, a test to monitor disease progression and effectiveness of
Let’s make guidelines simple that are easy to follow by primary care
providers – the frontline of healthcare in all regions around the world.
My simplified approach in assessing for kidney disease, irrespective
of if patient has diabetes or not, is:
1. First, do simple urinalysis or urine dipstick for protein and
measure of kidney function – serum creatinine and estimation of eGFR
2. If urinalysis is negative for protein or weakly positive for protein,
then do ACR
3. If urinalysis is 2+ or higher for urine protein, then do UPR, than
4. Define underlying kidney disease process – may require referral to
5. Determine stage of Kidney function, as per current guidelines and guide
therapy and monitoring for complications of kidney disease.
1. Bauer C, Melamed M, Hostetter TH. Staging of Chronic Kidney
Disease: Time for a course correction. J Am Soc Nephrol 2008; 19:844-6.
2. Glassock RJ, Winearls C. An epidemic of chronic kidney disease: fact or
fiction? Nephrol Dial Transplant 2008; 23:1117-21.
Competing interests: No competing interests