Serum retinol, the acute phase response, and the apparent misclassification of vitamin A status in the third National Health and Nutrition Examination Survey

Abstract

Background: Serum retinol decreases transiently during the acute phase response and can thus result in misclassification of vitamin A status.

Objective: Our objective was to determine the prevalence of acute phase response activation in a representative sample of the US population, identify the factors associated with this activation, and determine whether persons with an active acute phase response have lower serum retinol concentrations.

Design: Data from the third National Health and Nutrition Examination Survey (NHANES III) were analyzed. A serum C-reactive protein (CRP) concentration >/=10 mg/L indicated an active acute phase response.

Results: Mean serum retinol was lowest in subjects aged <10 y and increased with age. Concentrations were higher in males than in females aged 20-59 y. The prevalence of a CRP concentration >/=10 mg/L was lowest in subjects aged <20 y (</=4%) and increased with age to a maximum of nearly 15%. An elevated CRP concentration was 2.4-fold greater in females than in males aged 20-59 y. Serum retinol was lower in subjects with elevated CRP concentrations.

Conclusions: Serum retinol increases with age and males have higher mean values than do females aged 20-59 y. The prevalence of a CRP concentration >/=10 mg/L also increases with age, is 2-fold greater in females than in males aged 20-69 y, and is associated with common inflammatory conditions. Thus, inflammation appeared to contribute to the misclassification of vitamin A status in the NHANES III population, and serum CRP is useful in identifying subjects who may be misclassified.