A 5-year-old child from a rural area presents with night blindness and conjunctival xerosis. The mother reports the child has had recurrent diarrhoeal illnesses. Which biochemical indicator best reflects long-term vitamin A status rather than recent intake?
- A Serum retinol
- B Retinol-binding protein
- C Relative dose response (RDR) test ✓
- D Breast milk retinol
Correct answer: C. Relative dose response (RDR) test
Explanation
The Relative Dose Response (RDR) test measures hepatic vitamin A stores by assessing the percentage rise in serum retinol after a small oral dose of vitamin A. It reflects liver reserves, not recent intake. Serum retinol is homeostatically controlled and only falls when stores are severely depleted.
Reference: WHO Indicators for Assessing Vitamin A Deficiency, 2011 ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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