Fig. 1

Study selection process. PRISMA chart modeled after Moher et al. [21]. BH4 = tetrahydrobiopterin; PAH = phenylalanine hydroxylase deficiency; PKU = phenylketonuria
Study selection process. PRISMA chart modeled after Moher et al. [21]. BH4 = tetrahydrobiopterin; PAH = phenylalanine hydroxylase deficiency; PKU = phenylketonuria