Does impaired renal function with a GFR of 31 correspond to stage 3b Chronic Kidney Disease (CKD)?

From the Guidelines

Yes, a GFR of 31 mL/min/1.73m² corresponds to Stage 3b Chronic Kidney Disease (CKD). CKD is classified into stages based on the estimated glomerular filtration rate (eGFR). Stage 3 is divided into two sub-stages:

• Stage 3a: eGFR 45-59 mL/min/1.73m²
• Stage 3b: eGFR 30-44 mL/min/1.73m² With a GFR of 31, the patient falls into Stage 3b CKD, as defined by the most recent and highest quality study 1. This indicates moderate to severe kidney damage with significantly reduced kidney function.

Management for CKD 3b typically includes:

1. Blood pressure control (target <130/80 mmHg)
2. Glycemic control if diabetic (target HbA1c <7%)
3. Lipid management
4. Dietary modifications (low sodium, moderate protein)
5. Regular monitoring of kidney function and electrolytes
6. Avoiding nephrotoxic medications
7. Consideration of referral to a nephrologist Patients at this stage should be monitored for complications such as anemia, bone disease, and metabolic acidosis. Early intervention can help slow the progression of kidney disease and prevent complications, as supported by the KDIGO guideline 2 and other studies 3, 4, 5.

The classification of CKD into stages based on eGFR is widely accepted and used in clinical practice, as seen in the studies from 2014 2, 2018 4, and 2021 1. The distinction between Stage 3a and 3b is important, as the risks of mortality and other outcomes vary greatly between these groups, as noted in the 2014 study 2.

In clinical practice, the management of CKD 3b should prioritize the reduction of cardiovascular risk factors, as the majority of patients with Stage 3 CKD do not progress to end-stage renal disease but die mainly from cardiovascular causes, as mentioned in the 2015 study 5. Regular monitoring of kidney function and electrolytes, as well as avoiding nephrotoxic medications, are crucial in slowing the progression of kidney disease.

Overall, the classification and management of CKD 3b should be based on the most recent and highest quality evidence, prioritizing the reduction of morbidity, mortality, and improvement of quality of life.

From the Research

Definition of Chronic Kidney Disease (CKD) Stages

• CKD is typically classified into five stages based on the glomerular filtration rate (GFR) 6.
• Stage 3 CKD is further subdivided into two subgroups: stage 3A (eGFR 45-59 mL/min/1.73 m2) and stage 3B (eGFR 30-44 mL/min/1.73 m2) 6.

Impaired Renal Function with a GFR of 31

• A GFR of 31 corresponds to stage 3B CKD 6.
• Patients with stage 3B CKD have a higher risk of adverse renal and cardiovascular outcomes compared to those with stage 3A CKD 6.
• The risk of renal failure in patients with stage 3B CKD is under-recognized in standard medical screening 7.

Management and Progression of CKD

• The management of patients with CKD emphasizes a current level of function as calculated from the modification of diet in renal disease glomerulofiltration rate equations (eGFR) and proteinuria for staging of CKD 8.
• Change in a patient's eGFR over time (renal function trajectory) is an additional and potentially more important consideration in deciding which patients will progress to the point where they will require renal replacement therapy (RRT) 8.
• Proteinuria/albuminuria is a primary determinant of renal trajectory, which may be slowed by medications that decrease proteinuria and/or aggressively lower blood pressure 8.