HTRA1 and age-related macular degeneration: Moreover, the in/del haplotype was associated with AMD phenotype leading to an increase of HTRA1 protein concentration in plasma samples (Japan, p < 0.001; India, p = 0.001; Australia, p < 0.001) and serum samples (Japan, p < 0.001; India, p = 0.0437; USA, p = 0.0475) (Fig. 3D and Table S3).