TABLE 3.

Excess risk from interaction between HLA-A*24:02 and HLA-B*38:02 alleles in CBZ-Induced MPE (logistic regression).

HLA-A*24:02	HLA-B*38:02	MPE, n	Controls, n	OR
+	+	5	1	7.29
+	−	26	27	1.40
−	+	13	9	2.11
−	−	96	140	1.0

CBZ, carbamazepine; HLA, human leukocyte antigen; MPE, maculopapular exanthema; OR, odds ratio.With the multiplicative model, the expected joint odds ratio was 2.95 (1.40 × 2.11) and the odds ratio of the multiplicative interaction was 2.47 (7.29/2.95). Under an additive model, the expected joint odds ratio was 2.51 (1.40 + 2.11–1) and the excess risk from interaction was 4.78 (7.29–2.51).