Which analyte must be measured to calculate the estimated glomerular filtration rate (eGFR)?

The estimated glomerular filtration rate (eGFR) is an important clinical measure used to assess kidney function and determine how well the kidneys are filtering blood. The primary analyte required to calculate eGFR is serum creatinine. Creatinine is a byproduct of muscle metabolism that is produced at a relatively constant rate and is excreted by the kidneys. Because creatinine levels in the serum can indicate how well the kidneys are functioning, measuring serum creatinine provides a reliable estimate of the kidney's filtration capabilities.

While other elements such as body surface area can be utilized in the calculations for eGFR, they do not stand alone; thus, they do not serve as the primary analyte. For example, the most commonly used equations to estimate GFR, such as the Cockcroft-Gault or the MDRD (Modification of Diet in Renal Disease) equation, use serum creatinine values as the foundational component. Additionally, 24-hour urine volume and urine creatinine are not utilized to calculate eGFR directly, as they involve different assessments of kidney function. Therefore, serum creatinine is the crucial component required for the calculation of eGFR.