Association of carbamazepine-induced severe cutaneous drug reactions and HLA-B*1502 allele status, and dose and treatment duration in paediatric neurology patients in Singapore.

OBJECTIVES: To determine the association between severe cutaneous drug reactions (SCDR), HLA-B*1502 allelism, carbamazepine dose and treatment duration in a Singapore paediatric population. METHOD: Case-control study of SCDR with carbamazepine and HLA-B*1502. We recruited 32 cases, 5 with Steven Johnson Syndrome/Toxic Epidermolytic Necrolysis (SJS/TEN) (2 Chinese, 3 Malay), 6 with hypersensitivity syndrome (HSS) (5 Chinese, 1 Indian), 11 with minor drug reactions (9 Chinese, 2 Malay) and 10 controls (7 Chinese, 2 Malay, 1 Indian). HLA-B*1502 allelism was assayed. HLA-B*1502 status and the type of drug reaction were compared using univariate analysis. The time-span from treatment onset to reaction and the dose-time to reaction association in the 3 groups were analysed. RESULTS: HLA-B*1502 was positive in: 5/5 (SJS/TEN), 0/6 (HSS), 1/11 (minor drug reactions) and 1/10 controls. OR for SJS/TEN in HLA-B*1502-positive patients relative to that in HLA-B*1502-negative patients was estimated by exact logistic regression to be 27.20 (95% CI 2.67 to ∞). Median treatment duration (days) until allergic reactions was 12 (range 11-13), 16 (range 10-37) and 11 (range 0-63) for SJS/TEN, HSS and minor drug reactions, respectively. Median dose at onset of reactions was 6.2 mg/kg/day (range 4.6-7.4), 9.8 mg/kg/day (range 7.7-12.2) and 6.7 mg/kg/day (range 3.6-20.0) for the 3 groups, respectively. CONCLUSIONS: HLA-B*1502 positivity increases the odds of carbamazepine-induced SCDR in Singapore children of Chinese and Malay ethnicity. Adverse drug reactions to carbamazepine occurred within 2 weeks and at low doses.

Rapid prenatal diagnosis of common beta-thalassemia mutations in Southeast Asia using pyrosequencing.

OBJECTIVE: Current methods of prenatal diagnosis to detect beta-thalassemia are Sanger sequencing and reverse dot blot. These methods are time-consuming and can prolong assay turnaround time. We aim to develop a sensitive and rapid method to detect 27 beta-thalassemia mutations using pyrosequencing. METHOD: Pyrosequencing primer pairs and sequencing primers were designed to detect 27 most common beta-thalassemia mutations found in Singapore. Pyrosequencing was performed on 191 DNA samples with known beta-thalassemia mutations isolated from 143 peripheral blood and 48 prenatal samples (seven chorionic villus biopsies, 26 cultured amniocytes, 15 uncultured amniocytes). All mutations were validated with Sanger sequencing. RESULTS: Pyrosequencing identified 210 alleles with beta-thalassemia mutations and 82 alleles without mutations with 100% sensitivity (lower 95% confidence interval [CI], 97.8%) and 100% specificity (lower 95% CI, 94.4%). All pyrosequences were concordant with Sanger-based sequences. Pyrosequencing was able to detect DNA concentrations as low as 2 ng, obviating the need for cell culture in volume-restricted samples. Sample receipt-to-report assay turnaround times were 16 to 18 h (Sanger sequencing) and 4 to 6 h (pyrosequencing). CONCLUSION: Pyrosequencing is a rapid and sensitive method to detect common beta-thalassemia mutations without the need for cell culture, thus reducing the assay turnaround time.