Carbamazepine is a group of effective and affordable drugs to treat epilepsy, Autism, and Trigeminal Neuralgia. Patients are required to take the medicine for over a long period of time to keep the symptoms in check. The side effect – known as Stevens-Johnson Syndrome, whose symptoms include rash and shedding of skin and lips, feverish, in some cases blind and death – is rare but serious.
Recent studies show that patients of Asian ethnicity has “HLA-B*15:02” allele are high-risk of being allergic to Carbamazepine. Therefore, a screening of the allele would help determine whether to avoid the drug. This is a standard practice per FDA in the USA though is a work-in-progress in Thailand.
Even though the HLA-B*15:02 screening kit are available for sale but they are pricey while also require expensive tools and skilled technique to administer. In addition, some of the kits often yield false positives among SE Asians. Due to these limitations, a team of PSU researchers from Department of Pathology, Faculty of Medicine, including Dr. Kanoot Jaruthamsophon, Dr. Thanya Sri-Po and Associate Professor Dr. Pornprot Limprasert, developed HLA-B*15:02 screening method, with assistance from Assistant Professor Pharmacist Dr. Chonlaphat Sukasem, Head of Pharmacogenomics and Personalized Medicine, Somdech Phra Debaratana Medical Center, Ramathibodi Hospital, and additional sponsorship from the research fund of Faculty of Medicine, PSU. The research aimed to develop a screening kit that would be better-suited for Thailand and aid physicians, patients and hospitals.
Methods and qualifications
The Screening Kit to predict allergy reaction to Carbamazepine is to detect HLA-B*15:02 allele from the DNA. The screening must always be done prior to prescribing the medicine by using patient’s blood sample
The kit requires 2-step methods to confirm the result: Firstly, an allelle-specific PCR technique is employed to increase specific DNA. Negative result clears the patients to use Carbamazepine. Patients with positive results would need to go through second step called direct dot blot hybridization which tests DNA sample on a nylon plate. Colored dots (shown in picture) indicate positive result, which also means the patient has HLA-B*15:02 allele and should be prescribed any type of medicine other than Carbamazepine. The negative result, on the other hand, means the patient is not at risk to use Carbamazepine.
The innovation has been proven to provide highly-accurate prediction. The kit was able to detect HLA-B*15:02 accurately out of 155 DNA samples without yielding any false negatives while also showing positive result in samples that have no HLA-B*15:02. The cost of each kit is no more than 1,000 Baths, which is approved by Department of Medical Science. The innovation can be used in hospital settings to help physicians determine which medicine is appropriate to prescribe and ensure that the treatment is safe and effective. Outstanding features include easy to use, affordable, accurate, utilize common lab tools and most importantly suitable within the context of Thais and other SE Asian populations. The development is scheduled to conclude at the end of 2015.
Pictures: Showing methods and results of the screening (1) allele-specific PCR. Positive result shows 2 stripes while negative result shows one stripe (2) Positive result (in secondary step) shows colored dots
Department of Pathology, Faculty of Medicine, Prince of Songkla University
Source : http://rdo.psu.ac.th/