What test is used for assessing vitamin A status? Why?

What test is used for assessing vitamin A status? Why?

• A. Plasma carotenoid level
• B. Serum retinol concentration is used to assess vitamin A status because it correlates with dietary intake of vitamin A.
• C. Plasma transthyretin-retinol binding protein (TTR-RBP) concentration
• D. Serum retinol binding protein level

Answer: (B)

The key idea is that vitamin A status is best assessed with a direct biomarker that reflects body stores. Measuring serum retinol concentration serves this purpose because retinol levels in the blood stay within a narrow range when liver stores are adequate and only fall when stores are depleted. This makes serum retinol a practical indicator of overall vitamin A status and deficiency. Inflammation, infection, or liver disease can affect other markers or the appearance of retinol-bound proteins, and carotenoids reflect intake rather than true body stores, with conversion to retinol varying between individuals. Therefore, serum retinol concentration provides the most direct and clinically useful assessment of vitamin A status.

The key idea is that vitamin A status is best assessed with a direct biomarker that reflects body stores. Measuring serum retinol concentration serves this purpose because retinol levels in the blood stay within a narrow range when liver stores are adequate and only fall when stores are depleted. This makes serum retinol a practical indicator of overall vitamin A status and deficiency. Inflammation, infection, or liver disease can affect other markers or the appearance of retinol-bound proteins, and carotenoids reflect intake rather than true body stores, with conversion to retinol varying between individuals. Therefore, serum retinol concentration provides the most direct and clinically useful assessment of vitamin A status.