What's New About the New CKD Guideline?

Andrew Levey, MD, FNKF

KDIGO has recently released a new CKD practice guideline, updating the 2002 NKF-KDOQI guideline. The rationale for the guideline update was "to provide state-of-the-art guidance on the evaluation, management and treatment for all patients with CKD. Specifically, the guideline retains the definition of CKD but presents an enhanced classification framework for CKD; elaborates on the identification and prognosis of CKD; discusses the management of progression and complications of CKD; and expands on the continuum of CKD care: timing of specialist referral, ongoing management of people with progressive CKD, timing of the initiation of dialysis, and finally the implementation of a treatment program which includes comprehensive conservative management." This was an ambitious undertaking for KDIGO and has broad implications for clinical practice. In these paragraphs, we'll summarize what's new and not new about the definition and classification of CKD.

The KDIGO definition for CKD is not new. "CKD is defined as abnormalities of kidney structure or function, present for >3 months, with implications for health," and requires one of two criteria documented or inferred for >3 months: either GFR <60 ml/min/1.73 m2 or markers of kidney damage, including albuminuria. Since this definition is unchanged from the KDOQI definition, the previously reported prevalence estimates for CKD in the US and risk relationships are unchanged:

• CKD is common. The KDIGO guidelines endorse the CKD-EPI equation for GFR estimation, as it is more accurate for estimating measured GFR and risk. According to revised prevalence estimates, CKD affects 11.5% of US adults (23 million).
• CKD is harmful; it is an independent risk factor death, cardiovascular disease, and a broad range of complications, as well as kidney outcomes, kidney failure and acute kidney injury. Recent data from the CKD Prognosis Consortium, which conducted analysis for the guideline workgroup, shows that risk is increased for all subgroups defined by age, sex, ethnicity and diabetes and hypertension status. No subgroup that meets the criteria for CKD is free from increased risk.

The KDIGO classification for CKD is new. "CKD is classified based on cause, GFR category, and albuminuria category (CGA)." Previously CKD was classified into 5 stages according to GFR alone, but guidelines for evaluation and treatment had specifically recommended ascertaining the cause of disease and level of albuminuria or proteinuria, so what's new is primarily a matter of emphasis, rather than actions.

• The emphasis on cause of disease encourages clinicians to make a specific diagnosis when possible. Most kidney diseases in the US are due to hypertension or diabetes, and past and current KDOQI and KDIGO guidelines are applicable. However, for patients whose clinical characteristics do not fit these clinical diagnoses, clinicians are encouraged to undertake additional evaluation and to refer the patient to a nephrologist as necessary.
• GFR category 3 (30-59 ml/min/1.73 m2) is subdivided into 3a (45-59 ml/min/1.73 m2) and 3b (30-44 ml/min/1.73 m2) because of the large number of people in this category (6.2% of US adults, 12.4 million), and the generally worse prognosis of patients in category 3b vs. 3a. Previous guidelines directed toward patients with CKD stages 1-5 remain applicable for patients with GFR categories 1-5.
• The inclusion of albuminuria for all GFR categories recognizes the importance of albuminuria in defining risk and individualizing treatment. The three categories correspond to albumin-to-creatinine ratio (ACR) <30, 30-300, and >300 mg/g, corresponding to what was previously referred to normoalbuminuria, microalbuminuria and macroalbuminuria (these terms are no longer used). Patients with ACR >30 mg/g have increased risk for all outcomes mentioned above, and current guidelines recommend lower blood pressure targets (<130/80 mm Hg) using an ACE inhibitor or ARB. Conversely, patients with ACR <30 mg/g are generally are at lower risk and guidelines recommend the usual blood pressure (<140/90 mm Hg) using any antihypertensive medication.