Which test method is primarily used to assess renal function?

Serum creatinine is widely accepted as a primary test method for assessing renal function. Creatinine is a waste product that results from the normal breakdown of muscle tissue and is produced at a relatively constant rate in the body. The kidneys filter creatinine from the blood, and its concentration in serum reflects how effectively the kidneys are functioning. Elevated serum creatinine levels can indicate impaired kidney function, while levels within the normal range suggest that the kidneys are filtering appropriately.

While other methods like the 24-hour urine test and blood urea nitrogen can provide useful insights into kidney health, serum creatinine is often preferred for its simplicity, consistency, and direct reflection of glomerular filtration rate (GFR), which is a critical measure of kidney function. Urine analysis can provide additional information about various aspects of kidney function and potential urinary tract issues, but it does not serve as a direct assessment of renal function in the same way that serum creatinine does.