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

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

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.

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.

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.

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.