Which factor is considered when determining eGFR using the appropriate formula?

The correct choice is related to the importance of serum creatinine concentration when calculating estimated glomerular filtration rate (eGFR). eGFR is a critical parameter used to assess kidney function, and it estimates how well the kidneys are filtering waste from the blood.

Serum creatinine is a waste product generated from muscle metabolism and is normally excreted by the kidneys. Elevated levels of serum creatinine indicate impaired kidney function, making it a key factor in determining eGFR. The most widely used equations for calculating eGFR, such as the MDRD (Modification of Diet in Renal Disease) and the CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) formulas, directly incorporate serum creatinine concentrations. These calculations also adjust for factors like age, gender, and race, but it is serum creatinine that is the primary determinant in the estimation itself.

In contrast, while measurements like blood glucose levels, serum electrolytes, and body surface area can be relevant in broader clinical assessments of a patient's overall health or specific conditions, they do not play a direct role in the calculation of eGFR. Thus, the focus remains on serum creatinine as the essential variable for assessing renal function.