Plasma cytokine concentrations of children with autism spectrum disorder and neurotypical siblings.

• Plasma cytokines were assessed in children with autism and their siblings. • Plasma G-CSF was associated with an increased risk of being diagnosed as an ASD. • The overall cytokine profile of siblings and ASD children was very similar. • There is a need to consider if the controls are siblings of ASD children or not. Several studies of autism spectrum disorder (ASD) have shown cytokine dysregulation in children with ASD, leading to a consideration of the immune theory of the ASD etiopathogenesis and a debate about cytokines as potential biomarkers of ASD. However, the results of these studies are still inconsistent. Overall, studies comparing the cytokine levels of children with ASD and neurotypical siblings achieved relatively different results than studies with control groups of non-siblings. The studies suggest that the immune profile of siblings of individuals with ASD serving as control is more similar to children with ASD than the profile of non-siblings. However, there are still only a few studies with control groups including neurotypical siblings of children with ASD. The aim of our study was to determine whether the concentration of plasma cytokine levels may differentiate children with ASD from their neurotypical siblings. The sample consisted of 40 children with ASD (mean age 7.11 years, SD 2.9) and 21 neurotypical siblings (mean age 7.38, SD 3.3). Levels of 20 cytokines were included into the statistical analysis. A multiple logistic regression model using multiple corrections showed that an increase in log-transformed plasma G-CSF (granulocyte colony stimulating factor) concentration is associated with an increased risk of the child being diagnosed as an ASD case (OR = 4.35, 95% CI 1.77, 10.73). Although the significantly increased concentration of G-CSF suggests a slightly different activity of the immune system of children with ASD, the overall cytokine profile of their siblings appeared to be very similar. [ABSTRACT FROM AUTHOR]