Translations:Vitamin B6/43/en

Diagnosis

The assessment of vitamin B₆ status is essential, as the clinical signs and symptoms in less severe cases are not specific. The three biochemical tests most widely used are plasma PLP concentrations, the activation coefficient for the erythrocyte enzyme aspartate aminotransferase, and the urinary excretion of vitamin B₆ degradation products, specifically urinary PA. Of these, plasma PLP is probably the best single measure, because it reflects tissue stores. Plasma PLP of less than 10 nmol/L is indicative of vitamin B₆ deficiency. A PLP concentration greater than 20 nmol/L has been chosen as a level of adequacy for establishing Estimated Average Requirements and Recommended Daily Allowances in the USA. Urinary PA is also an indicator of vitamin B₆ deficiency; levels of less than 3.0 mmol/day is suggestive of vitamin B₆ deficiency. Other methods of measurement, including UV spectrometric, spectrofluorimetric, mass spectrometric, thin-layer and high-performance liquid chromatographic, electrophoretic, electrochemical, and enzymatic, have been developed.