Clinical Chemistry 46: 1867-1868, 2000;
(Clinical Chemistry. 2000;46:1867-1868.)
© 2000 American Association for Clinical Chemistry, Inc.
Assessment of Vitamin B1 Status
John McLaren Howard
Biolab Medical Unit, 9 Weymouth St., London W1 N 3FF, United Kingdom
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To the Editor:
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The excellent report by Talwar et al. (1) promotes
the measurement of thiamin diphosphate (TDP) for the assessment of
vitamin B1 status. My experience with >30 000
people supports this, but only for the investigation of untreated
patients.
The TDP assay is more precise than the transketolase activation (ETK)
test, and the method described is an important advance for which I
thank the authors. In comparing the two methods, Talwar et al.
(1) found TDP slightly advantageous in the identification of
B1 deficiency. They and most workers using the
ETK test agree that the cutoff point is 25%. I have found it useful to
report results in the range 15–25% as borderline. When this is done,
there is little to choose between TDP and ETK in terms of clinical
usefulness.
Much as I would like to use the more precise TDP assay, there is a
problem that surfaces when one wishes to use the laboratory to follow
repletion with thiamin. It is very rare for the TDP concentration to
remain low after a few days of supplemental B1,
and in many cases, TDP normalizes after a single 100-mg dose. This is
not the case for the ETK test. In some cases, several weeks of daily
supplementation are needed to normalize the results.
I am in the fortunate position of receiving considerable feedback from
the clinicians using our laboratory service and have carefully studied
their findings in relation to the laboratory results. In my experience,
it is the ETK test that parallels the clinical improvement in
supplemented patients.
I support the use of the more precise TDP (HPLC method) in untreated
people, but I caution against its use in following supplementation. For
this, the ETK test, even with its many limitations, remains the method
of choice. A more precise method for measuring this enzyme would be
enormously helpful.
I hope this letter will open some further discussion on the use of
functional tests in nutrient-related clinical chemistry.
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References
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Talwar D, Davidson H, Cooney J, St JO’Reilly D. Vitamin B1 status assessed by direct measurement of thiamin pyrophosphate in erythrocytes or whole blood by HPLC: comparison with erythrocyte transketolase activation test. Clin Chem 2000;46:704-710.[Abstract/Free Full Text]
Assessment of Vitamin B1 Status :Drs. Talwar and St. JO’Reilly respond:
Dinesh Talwara and
Denis St. JO’Reilly
Department of Clinical Biochemistry, Macewen Building, Royal Infirmary, Glasgow G4 0SF, United Kingdom
a Author for correspondence.
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To the Editor:
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Dr. McLaren Howard makes an interesting observation relating to
the biochemical assessment of thiamin status in people supplemented
with the vitamin. In his experience, the indirect measurement of
thiamin status using the transketolase (ETK) activation assay
is clinically more useful than direct measurement of thiamin
diphosphate (TDP) concentrations in red cells in people repleted with
thiamin. Unfortunately, we are unable to comment on his observation
because no relevant data are presented.
Discrepancies between the ETK activation test and clinical signs of
thiamin deficiency have been reported previously, with several studies
reporting no relationship between ETK activation results and thiamin
intake (1)(2)(3)(4)(5). These discrepant findings have raised
questions about the usefulness of the ETK activation test as a sole
indicator of thiamin status.
Because a valid ETK activation response depends on a kinetically normal
enzyme (1)(6), certain disease states may affect
enzyme cofactor binding and hence the TDP activation effect
(6). Because of the potential difficulty in interpretation
of ETK activation effect in some disease states and the limitations of
enzyme activation tests in general, several authors have suggested the
use of more direct measures of thiamin status, such as TDP in whole
blood or plasma (4)(6)(7).
We would agree with Dr. McLaren Howard that further discussion is
required on the merits or otherwise of direct and indirect
measures of thiamin status in patients repleted with thiamin.
Meanwhile, our experience with the HPLC assay suggests that measurement
of TDP in red cells is the single most useful biochemical measurement
for assessing thiamin status in patients who are at risk of thiamin
deficiency.
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References
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Kerr RA, Clague AE, Morris DJ, Price J. The rapid decline in erythrocyte transketolase on cessation of high dose thiamin administration in Korsakoff patients. Alcohol 1986;21:257-262.
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Iber FL, Blass JP, Brin M, Leevy CM. Thiamin in the elderly-relation to alcoholism and to neurological degenerative disease. Am J Clin Nutr 1982;36:1067-1082.[Abstract/Free Full Text]
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Nordentoft M, Timm S, Hasselbalch E, Roesen A, Gammeltoft S, Hemmingsen R. Thiamin pyrophosphate effect and erythrocyte transketolase activity during severe alcohol withdrawal syndrome. Acta Psychiatr Scand 1993;88:80-84.[Web of Science][Medline]
[Order article via Infotrieve]
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Gans DA, Harper AE. Thiamin status of incarcerated and nonincarcerated adolescent males: dietary intake and thiamin pyrophosphate response. Am J Clin Nutr 1991;53:1471-1475.[Abstract/Free Full Text]
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Macias-Matos C, Rodriguez-Ojea A, Chi N, Jimenez S, Zulueta D, Bates CJ. Biochemical evidence of thiamin depletion during the Cuban neuropathy epidemic 1992–1993. Am J Clin Nutr 1996;64:347-353.[Abstract/Free Full Text]
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McLaren DS, Docherty MA, Boyd DA. Plasma thiamin pyrophosphate and erythrocyte transketolase in chronic alcoholism. Am J Clin Nutr 1981;34:1031-1033.[Abstract/Free Full Text]
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Dancy M, Evans G, Gaitonde MK, Maxwell JD. Blood thiamin and thiamin phosphate ester concentrations in alcoholic and non alcoholic liver diseases. Br Med J 1984;289:79-82.
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To the Editor:
References
