title: The molar ratio of retinol-binding protein to transthyretin in the assessment of vitamin A status in adults. Proposal of a cut-off point.
abstract: The molar ratio of retinol-binding protein to transthyretin (RBP:TTR) has been proposed as an indirect method to assess vitamin A status in children with inflammation. Neither reference values nor appropriate cut-off point are available for adults. RBP, TTR and retinol were determined in plasma from 100 healthy adults and 31 low-risk surgical patients with no inflammatory response. RBP:TTR percentile distribution from 99 healthy adults with plasma retinol > or = 0.7 micromol/l was: 2.5th = 0.24; 5th = 0.31; 10th = 0.32; 25th = 0.41; 50th = 0.47; 75th = 0.54; 90th = 0.67; 95th = 0.78 and 97.5th = 0.81. In order to define a cut-off point, receiver operating characteristic (ROC) curve was constructed, using plasma retinol as gold standard. ROC curve was based on data from the 131 studied subjects, 11 of whom (8.4%) were classified as deficient on the basis of plasma retinol < 0.7 pmol/l. According to ROC curve criteria, RBP:TTR ratio was considered a good test, the area under the curve being 0.822, p < 0.001. A cut-off-point of < or = 0.37 is proposed to detect vitamin A deficiency in adults, since it allows reaching high sensitivity (81.8%), specificity (79.2%) and predictive value (79.4%). The proposed cut-off point falls between 13th and 14th percentiles.
authors.affiliation: Department of Nutrition and Food Science, School of Pharmacy and Biochemistry, University of Buenos Aires, Argentina. lzago@ffyb.uba.ar
authors.forename: Liliana B
authors.initials: LB
authors.lastname: Zago
authors.forename: Hernan
authors.initials: H
authors.lastname: Dupraz
authors.forename: María I
authors.initials: MI
authors.lastname: Sarchi
authors.forename: María E
authors.initials: ME
authors.lastname: Río
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011228:Prealbumin / Q000032:analysis*; D011237:Predictive Value of Tests; D012177:Retinol-Binding Proteins / Q000032:analysis*; D054839:Retinol-Binding Proteins, Plasma; D014801:Vitamin A / Q000097:blood*; D014802:Vitamin A Deficiency / Q000097:blood*
chemical_list: D011228:Prealbumin; D012177:Retinol-Binding Proteins; D054839:Retinol-Binding Proteins, Plasma; D014801:Vitamin A