Supplementary Material for: Surfactant Protein A Associated with Respiratory Distress Syndrome in Korean Preterm Infants: Evidence of Ethnic Difference

<b><i>Background:</i></b> Insufficiency of the pulmonary surfactant system is the primary cause of respiratory distress syndrome (RDS) in preterm infants. Genetic factors, including specific single-nucleotide polymorphisms in the genetic components of surfactant protein A (SP-A1 and SP-A2), affect protein structure and function, as well as risk of RDS. <b><i>Objective:</i></b> We investigated the association between variations in SP-A genotypes and RDS within the genetically homogeneous Korean population. <b><i>Methods:</i></b> We used TaqMan® real-time polymerase chain reaction technology to assess nine single-nucleotide polymorphisms of SP-A in 261 full-term and 152 preterm infants. Among the preterm infants, 76 infants with RDS were matched with 76 control infants with respect to gestation, use of antenatal steroids and gender. <b><i>Results:</i></b> The SP-A2 1A⁰ variant and the homozygous 1A⁰/1A⁰ genotype were associated with protection from RDS (OR 0.31, 95% CI 0.13–0.78). In addition, the 1A<sup>1</sup> carrier genotype (containing one copy of the 1A<sup>1</sup> variant) was associated with increased risk of RDS (OR 2.42, 95% CI 1.06–5.52). The significance of these results is that the association of patterns with RDS was opposite to the findings of previous research with Finnish and North American study populations. <b><i>Conclusions:</i></b> We have identified associations between specific variants of the SP-A genes and RDS risk in the Korean preterm study population. Our data strongly support SP-A as a candidate gene for susceptibility to RDS, and reveal the dissimilarity of the associated risk/protective genetic variants between different ethnic study populations.