Age and gender-related reference values for serum dl-alpha-tocopherol and all-trans-retinol levels in Saudi...

We established a reference range for dl-alpha-tocopherol and all-trans-retinol in a Saudi population previously selected for a cross-sectional study evaluating selenium and vitamin status. Concentrations of dl-alpha-tocopherol and all-trans-retinol were 0.999 +/- 0.31 mg/dL (n=994, range 0.11-3.42 mg/dL) and 49.14 +/- 24.15 micro/dL (n=1000, range 11.20-400.85 microg/dL), respectively. The levels of dl-alpha-tocopherol and all-trans-retinol in serum were determined by high-pressure liquid chromatography (HPLC) equipped with a UV detector. We took the influence of age and gender into account. Both had significant effect on the levels of all-trans-retinol in serum, except in the case of dl-alpha-tocopherol, where no gender related effect was found. We used the 5th and 95th percentiles as reference limits. Based on these criteria, it was found that these reference limits differed between genders for all-trans-retinol. Our lower and upper limits for dl-alpha-tocopherol classified by three age groups were very close to the normal range of 0.5-1.6 mg/dL, as found in previous studies. The 5th percentile of all-trans-retinol in both males and females, stratified by age, was close to a level of <20 microg/dL, which could be regarded as a mild vitamin A deficiency according to WHO criteria. But the value corresponding to the 95th percentile was higher than the upper limit of vitamin A's normal range of 70 microg/dL, suggesting a potentially harmful high dietary intake of vitamin A. The reference intervals elaborated here may help in the assessment of the vitamin status and in detecting subjects at risk of developing pathologies associated with either excess intake or deficiency.