What is the difference between total protein and albumin in urine?

• A. Albumin is the only protein detected in urine, while total protein detects all proteins.
• B. Albumin measures all proteins in urine.
• C. Total protein is the same as albumin in urine.
• D. Total protein measures all proteins in urine; albumin is a major protein often used to screen diabetic nephropathy; microalbumin tests detect early renal disease.

Answer: (D)

In urine, there are many proteins, so the total protein test sums all of them to give an overall measure of protein leakage. Albumin testing, on the other hand, measures just one protein—the major one in plasma that is most readily detected when the kidney’s filtering units are beginning to fail. Because albumin is the first protein to appear in urine with early glomerular damage, it’s used to screen for diabetic nephropathy. Microalbumin testing goes even lower, detecting small amounts of albumin that indicate early renal disease before total protein becomes abnormal. So the total protein test versus the albumin test reflects a broad measurement of all urinary proteins versus a focused measurement on albumin, which is a sensitive early marker of kidney damage.