Comparison of the modified relative dose response (MRDR) and the relative dose response (RDR) in the assessment of vitamin A status in malnourished children

Academic Article


  • The modified-relative-dose-response (MRDR) test and the relative-dose- response (RDR) test were compared in 49 mildly to moderately malnourished Bangladeshi children. The MRDR test had a significantly lower sensitivity, detecting only 71% of children with very low serum retinol (≤ 0.35 μmol/L) and 33% of children with low serum retinol (0.355-0.70 μmol/L) compared with 100% and 80% for the RDR test, respectively. The MRDR test showed a very strong dependency on retinol-binding protein (RBP) saturation (ie, percent saturation of RBP with retinol) compared with the RDR test. Only 3 (23%) of 13 children with RBP saturation ≥ 55% but low vitamin A stores were diagnosed as abnormal by the MRDR test. This suggests that when apo-RBP concentration is limiting, as it is in malnourished children, didehydroretinol, the analog used in the MRDR test cannot effectively compete with retinol for binding to apo-RBP. Under these circumstances, the MRDR test is rendered ineffective. The possibility of increasing the sensitivity of the test by using a high dose of didehydroretinol needs to be investigated.
  • Authors

    Digital Object Identifier (doi)

    Pubmed Id

  • 19160689
  • Author List

  • Wahed MA; Alvarez JO; Khaled MA; Mahalanabis D; Rahman MM; Habte D
  • Start Page

  • 1253
  • End Page

  • 1256
  • Volume

  • 61
  • Issue

  • 6