Effects of a HLA-B*15:02 screening policy on antiepileptic drug use and severe skin reactions.

Abstract

To assess the effects of an active pharmacogenetic screening policy for antiepileptic drug (AED) therapy on everyday clinical practice and clinical outcomes. We extracted data covering all public hospitals and clinics in Hong Kong for patients who were newly commenced on carbamazepine or other AEDs, or were tested for HLA-B*15:02 3 years before policy implementation (prepolicy: September 16, 2005 to September 15, 2008) and 3 years after (postpolicy: September 16, 2008 to September 15, 2011). We compared AED prescriptions and the incidence of SJS/TEN between the 2 periods and analyzed adherence to the policy. A total of 111,242 patients were included and 4,149 were tested for HLA-B*15:02. As a proportion of all new AED prescriptions, carbamazepine declined from 16.2% (10,077/62,056) in the pre-policy period to 2.6% (1,910/74,606) in the post-policy period (p < 0.001) while other AEDs increased. Among patients started on their first-ever AEDs, incidence of Stevens-Johnson syndrome (SJS)/toxic epidermal necrolysis (TEN) induced by carbamazepine reduced from 0.24% (20/8,284) to 0% (0/1,076; p = 0.027), but SJS/TEN induced by phenytoin increased (0.15% [18/11,839] vs 0.26% [33/12,618], p = 0.058), and the overall incidence of AED-induced SJS/TEN remained unchanged (0.09% [42/45,832] vs 0.07% [39/55,326], p = 0.238). Test-prescription practice was adherent to the policy in only 26.4% (1,302/4,929) of relevant patients. The screening policy was associated with prevention of carbamazepine-induced SJS/TEN without reducing the overall burden of AED-induced SJS/TEN, likely because of clinicians preferring AEDs that do not require genetic screening but may also induce SJS/TEN.