Mean serum concentration of vitamin D-binding protein (Gc globulin) is related to the Gc phenotype in women.

cause mild overtreatment, i.e., a reduction in dietary Phe allowances in excess of metabolic tolerance. This is not critical with Phe concentrations at or above the upper limit of normal. Still, neurological outcome has also been demonstrated to be adversely affected by Phe deficiency (14 ). In view of an overestimation by up to 60 mmol/L in the low concentration range and a target range of 40–250 mmol/L in fresh samples, it would appear prudent to aim at Phe concentrations .100 mmol/L for samples measured after delayed preparation from whole blood. In conclusion, the clinical practice of delayed measurement of Phe and Tyr in whole-blood samples mailed to the specialized laboratory leads to slightly increased readings. This is clinically safe, as long as Phe concentrations are kept above 100 mmol/L to prevent Phe deficiency.