American Association of Critical-Care Nurses (AACN) Certification Practice Test

Which serum protein reflects nutritional status over the past week?

1. Serum albumin

2. Serum transferrin

3. Serum prealbumin

4. Serum bilirubin

The correct answer is: Serum prealbumin

The correct answer is serum prealbumin, which serves as a more accurate indicator of nutritional status over the past week. Prealbumin has a relatively short half-life of about 2 to 3 days, making it sensitive to changes in protein intake and nutritional status. When a patient's nutritional condition improves or deteriorates, serum prealbumin levels will reflect those changes much more quickly compared to other markers. While serum albumin is often used to assess nutritional status, it has a longer half-life of 20 days, which means it is less responsive to short-term changes in diet or nutrition. Consequently, albumin may not accurately represent a patient's current nutritional state. Serum transferrin, although it can indicate iron status and protein levels, typically has a half-life of about 8 to 9 days, and its levels can also be influenced by several other factors, such as inflammation or liver function. Serum bilirubin primarily serves to assess liver function and the breakdown of red blood cells, rather than nutritional status, and it is not a useful marker for evaluating dietary intake. Thus, serum prealbumin is the optimal choice for reflecting nutritional status in the short term, particularly over the past week.