Interpretation of vitamin A status in apparently healthy Pakistani children by using markers of subclinical infection

Background: Plasma retinol concentrations are depressed by infection but ar e commonly used to assess vitamin A status. Objective: We measured 2 acute phase proteins, alpha (1)-antichymotrypsin ( ACT) and alpha (1)-acid glycoprotein (AGP), to determine whether they could be used to assist in interpreting vitamin A status. Design: In 1997, a 2-stage cluster-sampling procedure was used to select 30 74 apparently healthy, 6-60-mo-old children from rural and urban areas of N orth West Frontier Province, Pakistan. Plasma retinol, ACT, AGP, and ferrit in measurements and anthropometric measurements were obtained for 2519 chil dren. Results: Median plasma retinol, ACT, AGP, and ferritin concentrations were 0.86 mu mol/L, 0.39 gn, 1.14 gn, and 5.5 mug/L respectively. There were no significant (P > 0.05) differences in retinol, ACT, or AGP by sex or age. S ome 797 children (32%) had retinol concentrations <0.7 <mu>mol/L and 87 (4% ) had retinol concentrations <0.35 <mu>mol/L; 274 children (11%) had elevat ed ACT (>0.6 g/L) and 1141 (45%) had elevated AGP (>1.2 g/L). Retinol conce ntration correlated with ACT (r = -0.141), AGP (r = -0.138), and ferritin ( r = -0.09) tall P < 0.001), but stepwise multiple regression indicated that these 3 variables made a minimal although quantifiable contribution to the variance of retinol (ACT, r(2) = 0.02; all 3 variables, r(2) = 0.03). Conclusions: The transient depression in plasma retinol produced by subclin ical infection increased the number of at-risk children by 10% (76 of 797) and 56% (49 of 87) for plasma retinol concentrations <0.7 and <0.35 <mu>mol /L, respectively. In addition, dietary inadequacy may be responsible for re tinol concentrations being approximate to 16% lower in Pakistani children t han in children in the United Kingdom, where dietary vitamin A is adequate.