Laboratory Studies
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The most rapid, and thus the best diagnostic test for beriberi in urgent situations, is observing a clinical response to administration of intravenous thiamine (few hours duration). [22]
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The most reliable in vitro laboratory tests involve measurement of whole blood or erythrocyte transketolase activity.
An enhancement of enzymatic activity from the in vitro addition of thiamine pyrophosphate (TPP) is referred to as the TPP effect.
An increase in the enzymatic activity of more than 15% strongly supports the diagnosis of thiamine deficiency.
A depressed blood level of thiamine can be seen.
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Elevated measurements of the following substances are characteristically noted because their metabolism depends on enzymes that have thiamine as their cofactors:
Pyruvate
Alpha-ketoglutarate
Lactate
Glycosylate
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Additional investigations that have been proposed as diagnostic tests include the following:
Urinary thiamine
Thiamine metabolites (thiazole or pyrimidine)
Methylglyoxal values
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Recent advances in technology has shown that thiamine concentration can also be determined in whole blood using high-performance liquid chromatography (HPLC). [23]
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Unexplained lactic acidosis that persists after fluid bolus should prompt consideration of beriberi.
Imaging Studies
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The Israeli infants who received the thiamine-deficient formula form the basis for the pediatric MRI descriptions in this condition. These infants had involvement of the frontal lobes and basal ganglia, in addition to the lesions present in the periaqueductal region, thalami, and the mammillary bodies that have been described in adults. The lesions that have been noted were described as symmetric and hyperdense. Brainstem involvement was noted. In small numbers of patients severe frontal damage was noted in long term follow-up with a loss of parenchyma and atrophy of the basal ganglia and thalami in some. [21]
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MR spectroscopy (MRS) reveals a characteristic lactate peak.
Other Tests
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Diffuse slowing of the EEG can be observed.
Procedures
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An intravenous push of thiamine is recommended in a deteriorating patient who has features suggestive of beriberi.
Histologic Findings
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The histologic lesions of wet beriberi have been reported to be due to degeneration of myelin in the muscular sheaths without inflammation.
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Beriberi.
