Background: According to the marketing survey by Taiwan Food and Drug Administration, carbamazepine is one of the most commonly used medicine that caused severe adverse reaction, such as Stevens-Johnson syndrome or Toxic epidermal necrolysis. The rate of carbamazepine induced severe adverse reaction in Asian is higher than Caucasian. This adverse reaction had been proved to be HLA-B 1502 genotype-related, and the prevalence of HLA-B 1502 genotype was higher in Asian. Therefore, Taiwan had included HLA-B 1502 genotype testing in health insurance payment item in 2010.
Objectives: Analyze the HLA-B 1502 genotype testing rate on carbamazepine new user in 2019 and compare the difference between testing verse non-testing group.
Methods: A retrospective case-control study based on a hospital clinical database in a hospital in Taiwan. First, find carbamazepine new user in 2019. Secondly, link new user to genotype testing data. Define those having HLA-B 1502 genotype testing before doctors prescribe carbamazepine as testing group, others as control group. Finally, statistical analysis the differences between two groups with SPSS 18. Finally, find the positive HLA-B 1502 genotype testing rate.
Results: There were 44 carbamazepine new users among 117 in 2019. In those new users, 18 were testing group, testing rate was 40.9% and 26 were control group. There was no significant difference in age, gender between two groups, but difference in the place of medical treatment. The medical treatments in testing group were mostly took place in outpatient and prescribed by Neurologist, while the other group were partly outpatient, partly inpatient and carbamazepine were prescribed by physicians in various departments. No severe adverse effects happened in both group. Furthermore, there were total 24 HLA-B 1502 genotype testing, only 1 showed positive result. Positive rate was 4.2%.
Conclusions: Carbamazepine had launched over 20 years in Taiwan, and be one of the most widely used medicine for seizure in Taiwan. Taiwan included HLA-B 1502 testing in health insurance payment since 2010, but there aren’t any HLA-B 1502 genotype testing survey in real world data. Although many guidelines suggests that physicians should give HLA-B 1502 genotype testing for carbamazepine new user, the testing rate is still low according to this study. This result could be patients refused to do more blood testing, non-neurologists with in-sufficient knowledge to test HLA-B 1502 genotype, not necessary for inpatient to test HLA-B 1502 genotype. Reasons are still need to be proved by further study. Moreover, the positive HLA-B 1502 rate reported in this survey is 4.2%, on the contrary to previous studies 1-5%.
