Health economic evaluation of gene replacement therapies: methodological issues and recommendations by Aballéa, S, Thokagevistk, K, Velikanova, R, Simoens, S, Annemans, L, Antonanzas, F, Auquier, P, François, C, Fricke, F-U, Malone, D, Millier, A, Persson, U, Petrou, S, Dabbous, O, Postma, M, Toumi, M