Comparison of methods of assessing vitamin A status in children.
OBJECTIVE
A study of children (2-8 years; n = 613) in Belize, Central America, was conducted to determine what proportion of the children might be at risk of vitamin A (vit A) deficiency. The data provide an opportunity to compare results of three methods of assessing vit A status in a population which was not severely malnourished. Serum retinyl ester concentrations were also determined; their relevance to one of the tests, the relative dose response (RDR) test, is discussed.


METHODS
The three methods of assessing vit A status were: RDR test, fasting serum retinol concentration, and conjunctival impression cytology (CIC). Retinol-binding protein (RBP), serum retinyl esters and serum zinc concentrations were also determined.


RESULTS
Inadequate vit A status was indicated for 17% of subjects by the RDR test (14% cutoff), for 24% by fasting serum retinol concentration (< 0.87 mumol/L), and for 49% by "abnormal" CIC score. Retinyl esters constituted 24% of serum retinoids at the time (5 hours after a retinyl palmitate dose) at which the second blood sample is taken for the RDR test. Regression tree analyses (CART) indicated ethnicity was a predictor of RDR score; ethnicity, stunting and age were predictors of fasting serum retinol concentration; ethnicity and stunting were predictors of 0-hour retinyl ester concentration.


CONCLUSIONS
The three indices of vit A status did not identify the same individuals nor indicate the same percentage of the population to be at risk for vit A deficiency. Increased concentrations of retinyl esters at 5 hours compared to those at 0 hours suggest that insufficient retinol may have been taken up by the liver at 5 hours to release all accumulated retinol-binding protein (RBP) in deficient individuals; prevalence of vit A deficiency might therefore be underestimated by the RDR test. The selection of ethnicity as a predictor of RDR score and of 0-hour retinol and retinyl ester concentrations suggests that factors other than vit A status affect vit A metabolism and may affect the RDR test.
Makdani
D
D
Lincoln University, Jefferson City, Missouri 65102-0029, USA.
Sowell
A L
AL
Nelson
J D
JD
Apgar
J
J
Gunter
E W
EW
Hegar
A
A
Potts
W
W
Rao
D
D
Wilcox
A
A
Smith
J C
JC
D001531:Belize; D002648:Child; D002675:Child, Preschool; D002851:Chromatography, High Pressure Liquid; D005006:Ethnicity; D005260:Female; D006801:Humans; D008297:Male; D009752:Nutritional Status; D012307:Risk Factors; D014801:Vitamin A / Q000097:blood*; D015032:Zinc / Q000097:blood
D014801:Vitamin A; D015032:Zinc