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Re: Fits, pyridoxine and hyperprolinaemia type II

Currently two types of measurements are used to assess (chemical and functional) vitamin B6 status, which measure directly B6 and its metabolites and activation of vitamin B6 dependent enzymes and associated aminoacids. The load tests are also used to reveal the subtle defects by stressing the B6 metabolic pathway. None of them is ideal and a combination of them is recommended. Additionally there is no concordance between these indices. Transaminase activity in serum and red blood cell (functional index) decreases along with plasma PLP (pyridoxal phosphate, urine B6 and pyridoxic acid (direct chemical index)) within 1 week after removal vitamin B6 from the diet. Electromyelographic abnormalities appear within 3 weeks (1).

Some population groups in modern society have a suboptimal intake with or without excess protein intake, although severe vitamin B6 deficiency is uncommon in man (2). Epileptiform convulsions are a common finding in young vitamin B6 deficient subjects (1). These (sub)clinical deficiencies can be screened routinely by a clinical laboratory even in a small remote village if a simple test like transaminases are used which is easily available on (semi)automated chemistry analysers. Vitamin B6 deficiency in a well nourished child with an autosomal recessively inherited pyrroline-5-carboxylate dehydrogenase deficiency led to childhood fits, because of binding of the proline metabolite, pyrroline-5-carboxylate with vitamin B6 reported by Walker et al (3). It is very interesting to know if the authors had measured the transaminases (and by which method) as some method come with PLP supplement), if not it would be interesting to know their view on this simplistic approach. Their transaminase results if significant will emphasise their usefulness as a cost and clinically effective screening test.

References:

1. Mccormick DB, Green HL. Vitamins. In: Burtis CA, Ashwood ER eds. Tietz text book of clinical chemistry, 3rd ed. Pennsylvania: W.B.Saunders. 1999:1016-18.

2. Bates CJ. Vitamin analysis. Ann Clin Biochem 1997; 34: 599-626.