title: Comparison of the modified relative dose response (MRDR) and the relative dose response (RDR) in the assessment of vitamin A status in malnourished children.
abstract: 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 (< or = 0.35 mumol/L) and 33% of children with low serum retinol (0.355-0.70 mumol/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 > or = 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.affiliation: International Center for Diarrheal Diseases Research ICDDR, B, Dhaka, Bangladesh.
authors.forename: M A
authors.initials: MA
authors.lastname: Wahed
authors.forename: J O
authors.initials: JO
authors.lastname: Alvarez
authors.forename: M A
authors.initials: MA
authors.lastname: Khaled
authors.forename: D
authors.initials: D
authors.lastname: Mahalanabis
authors.forename: M M
authors.initials: MM
authors.lastname: Rahman
authors.forename: D
authors.initials: D
authors.lastname: Habte
mesh_terms: D002675:Child, Preschool; D002851:Chromatography, High Pressure Liquid; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D009748:Nutrition Disorders / Q000378:metabolism*; D009752:Nutritional Status; D012177:Retinol-Binding Proteins / Q000378:metabolism; D014801:Vitamin A / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000097:blood / Q000378:metabolism
chemical_list: D012177:Retinol-Binding Proteins; C024366:vitamin A2; D014801:Vitamin A