Evaluation of vitamin A status during an acute illness

We examined the effect of an acute infectious episode on serum retinol and on the Relative Dose Response (RDR) test in a group of 1-3 year old children in rural Bangladesh. Sixty children were followed for 3 months after receiving supplementation with high dose vitamin A (200,000 IU). Using plasma retinol and the RDR test, vitamin A status was assessed at 3 weeks and 3 months after supplementation. Thirteen of the 60 (22%) children were acutely ill at the time of the initial assessment. Three children had pneumonia with fever; three had bloody diarrhea with fever; six had diarrhea, 4 with and 2 without fever; one had only fever. Those subjects who were ill at the time of the assessment had significantly lower plasma retinol (mean 18.3μg/dl vs. 25.1μg/dl; p+0.0029) and significantly higher RDR test results (23.7 vs. 11.8; p=0.0004) compared to those children who were healthy. Additionally, in the 13 children who were ill at the time of the initial assessment, plasma retinol levels measured 3 months later became normal compared to the initial low level (26.6μg/dl vs. 18.4μg/dl; p=0.0254). These data indicate that during an acute illness low plasma retinol levels or a positive RDR test are not necessarily a reflection of decreased vitamin A stores. The decreased bioavailability of vitamin A during an acute infectious event is probably associated with decreased circulating levels of the transport proteins retinol binding protein and transthyretin. In conclusion, the assessment of vitamin A status at the time of an acute illness using plasma retinol or RDR test will provide mis-leading results by underestimating true vitamin A stores.