Thyroid Hormone Levels in Children Receiving Antiepileptic Drugs

We read the publication entitled “Is It Necessary to Measure Thyroid Hormone Levels in Children Receiving Antiepileptic Drugs?” with a great interest.[1] Aziz and ELela concluded that “The thyroid function tests were affected by the use of sodium (Na) valproate and carbamazepine compared to both the control group and the group taking newer anti-epileptic drug (AED) oxcarbazepine and levetiracetam. In addition, there was no effect of levetiracetam on thyroid function test results.”[1] In fact, the effect of drug on thyroid function test or other laboratory can be expected. Based on the laboratory medicine principle, the interference from drug is a common problem that might lead to the erroneous laboratory results. Focusing on patients with epilepsy, Isojärvi et al previously studied the effect of taking carbamazepine, oxcarbazepine, or valproate on thyroid function test.[2] Isojärvi et al found that valproate did not significantly affect thyroid function test.[2] The discordance observations reported by Isojärvi et al from Aziz and ELela is a very interesting issue. In addition to drug inteference, another important concern is on the preanalytical error. Several problems in the preanalytical phase of laboratory investigation can result in erroneous test results and these problems is not uncommon and is observable in the standardized, certified clinical laboratory.[3] In the present report by Aziz and ELela, whether there is an interference from other preanalytical factor in the observed thyroid function test results is an interesting question.

Editor's Note

Unfortunately, authors of the article, entitled “Is It Necessary to Measure Thyroid Hormone Levels in Children Receiving Antiepileptic Drugs?” published in Journal of Pediatric Epilepsy, did not send a response to this “Letter to the Editor.”

• References

• 1 Aziz RAA. ELela MAA. Is it necessary to measure thyroid hormone levels in children receiving antiepileptic drugs? J Pediatr Epilepsy doi:10.1055/s-0038-1648242
• 2 Isojärvi JI, Turkka J, Pakarinen AJ, Kotila M, Rättyä J, Myllylä VV. Thyroid function in men taking carbamazepine, oxcarbazepine, or valproate for epilepsy. Epilepsia 2001; 42 (07) 930-934
• 3 Wiwanitkit V. Types and frequency of preanalytical mistakes in the first Thai ISO 9002:1994 certified clinical laboratory, a 6-month monitoring. BMC Clin Pathol 2001; 1 (01) 5