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

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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 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.