Editing Vitamin B6 (section)

===Diagnosis===
The assessment of vitamin B<sub>6</sub> status is essential, as the clinical signs and symptoms in less severe cases are not specific.<ref>{{cite book|chapter-url=https://books.google.com/books?id=lBlu7UKI3aQC|title=Principles of Nutritional Assessment|vauthors=Gibson RS|publisher=Oxford University Press|year=2005|isbn=978-0-19-517169-3|edition=2nd|location=New York|pages=575–594|chapter=Assessment of vitamin B<sub>6</sub> status|lccn=2004054778|oclc=884490740|access-date=April 20, 2018|archive-date=December 31, 2023|archive-url=https://web.archive.org/web/20231231072056/https://books.google.com/books?id=lBlu7UKI3aQC|url-status=live}}</ref> 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 B<sub>6</sub> 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&nbsp;nmol/L is indicative of vitamin B<sub>6</sub> deficiency.<ref name=Ueland2015>{{cite journal |vauthors=Ueland PM, Ulvik A, Rios-Avila L, Midttun Ø, Gregory JF |title=Direct and Functional Biomarkers of Vitamin B6 Status |journal=Annu Rev Nutr |volume=35 |issue= |pages=33–70 |date=2015 |pmid=25974692 |pmc=5988249 |doi=10.1146/annurev-nutr-071714-034330 |url=}}</ref> A PLP concentration greater than 20&nbsp;nmol/L has been chosen as a level of adequacy for establishing Estimated Average Requirements and Recommended Daily Allowances in the USA.<ref name="DRItext" /> Urinary PA is also an indicator of vitamin B<sub>6</sub> deficiency; levels of less than 3.0&nbsp;mmol/day is suggestive of vitamin B<sub>6</sub> deficiency.<ref name=Ueland2015 /> Other methods of measurement, including [[Ultraviolet–visible spectroscopy|UV spectrometric]], [[Fluorescence spectroscopy|spectrofluorimetric]], [[Mass spectrometry|mass spectrometric]], [[thin-layer chromatography|thin-layer]] and [[High-performance liquid chromatography|high-performance liquid chromatographic]], [[Electrophoresis|electrophoretic]], [[electrochemistry|electrochemical]], and enzymatic, have been developed.<ref name=Ueland2015 /><ref>{{cite journal |vauthors=Ahmad I, Mirza T, Qadeer K, Nazim U, Vaid FH |title=Vitamin B6: deficiency diseases and methods of analysis |journal=Pak J Pharm Sci |volume=26 |issue=5 |pages=1057–69 |date=September 2013 |pmid=24035968 |doi= |url=}}</ref>

The classic clinical symptoms for vitamin B<sub>6</sub> deficiency are rare, even in developing countries. A handful of cases were seen between 1952 and 1953, particularly in the United States, having occurred in a small percentage of infants who were fed a formula lacking in pyridoxine.<ref name="TCN">{{cite book |url=https://books.google.com/books?id=og-0AAAAIAAJ |title=Textbook of Child Neurology |last=Menkes |first=John H. |publisher=Henry Kimpton Publishers |year=1980 |isbn=978-0-8121-0661-9 |edition=2nd |location=Philadelphia |page=486 |lccn=79010975 |oclc=925196268 |access-date=April 20, 2018 |archive-date=December 31, 2023 |archive-url=https://web.archive.org/web/20231231072058/https://books.google.com/books?id=og-0AAAAIAAJ |url-status=live }}</ref>