What laboratory test is primarily used to assess kidney function?

Serum creatinine is a crucial laboratory test used to assess kidney function because it reflects the kidneys' ability to filter waste products from the blood. Creatinine is a waste product generated from normal muscle metabolism and is produced at a fairly constant rate in the body, depending on muscle mass. Under normal circumstances, the kidneys filter creatinine out of the blood, and it is excreted in the urine.

An elevated serum creatinine level can indicate impaired kidney function, as the kidneys are unable to effectively remove this waste product. Creatinine levels can also be used to calculate the estimated glomerular filtration rate (eGFR), which is a more specific measure of kidney function.

While blood urea nitrogen (BUN) also serves as an indicator of kidney function, it can be influenced by factors unrelated to kidney disease, such as large protein intake or dehydration. Glomerular filtration rate (GFR) is indeed the most definitive measure of kidney function, but it is often calculated using serum creatinine levels along with other factors like age, sex, and race. Urinalysis provides valuable information about the state of the urinary system but is not as direct a measure of kidney function.

Therefore, serum creatinine serves as the primary laboratory test