Measured GFR does not outperform estimated GFR in predicting CKD-related complications

Area of Science:

• Nephrology
• Clinical Chemistry
• Epidemiology

Background:

• Glomerular filtration rate (GFR) is crucial for managing chronic kidney disease (CKD) and its complications.
• Iothalamate-measured GFR (iGFR) is often considered superior to equation-estimated GFR (eGFR).
• The clinical utility of iGFR versus eGFR in relation to CKD comorbidities remains unclear.

Purpose of the Study:

• To compare the clinical utility of iGFR and eGFR in assessing CKD-associated comorbidities.
• To determine the association strength between different GFR measures and CKD complications.

Main Methods:

• Cross-sectional analysis of 1214 participants from the Chronic Renal Insufficiency Cohort (CRIC) Study.
• Assessed associations between iGFR, eGFR estimated from serum creatinine (eGFR_Cr), and eGFR estimated from cystatin C (eGFR_cysC) with CKD complications.
• Compared the discriminative ability of each GFR measure for specific comorbidities.

Main Results:

• No GFR measure strongly associated with all CKD complications.
• iGFR showed better discrimination for anemia and hemoglobin levels compared to eGFR_Cr and eGFR_cysC.
• eGFR_Cr and eGFR_cysC demonstrated better discrimination for hyperphosphatemia and phosphorus levels than iGFR.
• iGFR and eGFR showed similar associations with hyperkalemia and metabolic acidosis.

Conclusions:

• Iothalamate-measured GFR is not consistently superior to equation-based estimations for explaining CKD-related comorbidities.
• The findings challenge the conventional view of iGFR as the definitive "gold standard" for kidney function assessment.
• Clinical utility of different GFR measures varies depending on the specific CKD complication being evaluated.