A recent study from Canada in the latest issue of JAMA Feb 3, 2010 talks about the inclusion of proteinuria in CKD staging. The current staging system of CKD puts more emphasis on GFR and the lower the GFR, the worse the outcome. Proteinuria has been noted to be marker of kidney damage as well( this is now also in debate). A community based cohort study done of adults for mean follow up of 35 months showed that the risks for all cause mortality, heart attacks, progression to kidney failure associated with a given level of GFR were independently increased among patients with higher levels of proteinuria.
At this point, if there is a patient with GFR Of 80ml/min and 3+ proteinuria, they would get assigned Stage I, even though their risks of death and need for dialysis might be 2-10 times higher than otherwise similar patient in Stage 3 with no proteinuria. They propose subdividing stage 3 in parts ( proteinuria, no proteinuria, so forth)
It's an observational study and it brings a good point back to the table. Is our classification system good? Does it help identify more risk patients? Do we need to include more parameters besides GFR? What about albumin as well?
The bigger question at debate is also:- is non nephrotic range proteinuria all bad? is it really a marker of kidney disease? Those are questions at debate even now among nephrologists