Abstract
BackgroundDespite the global increase in the prevalence of autism spectrum disorders (ASD), relevant research studies are lacking in Brunei Darussalam. Various studies have shown a significant association between a lowered 2D:4D ratio (ratio of second digit/index finger to the fourth digit/ring finger) and ASD, making it one of the potential phenotypic biomarkers for early detection of autism, which is important for early intervention and management.ObjectiveThe objective of this study is to explore the association between 2D:4D ratio and ASD in Brunei Darussalam, as a potential tool to complement early ASD diagnosis.MethodsWe conducted a case–control study comprising 28 ASD and 62 typically developing (TD) children in the case and control group, respectively (age range: 3–11 years old; median age: 6 years old). Median 2D:4D ratios were measured, compared and analysed between the two groups. Logistic regression models were used to explore potential associations between the median 2D:4D ratio and ASD in respective gender, for both left and right hands, independently.ResultsOur study shows that the median 2D:4D ratio of left hand in ASD males is significantly lower than those in TD males, after adjusting for ethnicity and age [Odds Ratio (OR) = 0.57 (95% Confidence Interval (CI): 0.31–0.96); p = 0.044]. For females, there is no association of ASD with the median left hand 2D:4D ratio [OR = 3.09 (95% CI: 0.98–19.86); p = 0.144] or the median right hand 2D:4D ratio [OR = 1.23 (95% CI: 0.42–3.88); p = 0.702]. Our study also shows a significant positive correlation and/or a reduced asymmetry between the average 2D:4D ratio of left hands and right hands in ASD males (Pearson’s correlation (r) = 0.48; 95% CI: 0.076–0.75, p = 0.023).ConclusionsThere is significant association between a lowered median 2D:4D ratio of the left hand (in males only) and ASD diagnosis. Once validated in a larger sample size, a lowered median 2D:4D ratio on the left hand may be a potential tool to complement ASD diagnosis for males in our study population. There is no association between the median 2D:4D ratio (left or right hands) and ASD in females, which could be due to the small female sample size and/or the possibility of different aetiology for ASD in females. Reduced asymmetry between the average 2D:4D ratio of left and right hands observed in ASD males only (not in ASD females) also suggests the importance of considering gender-specific biomarkers for ASD diagnosis.
Highlights
Autism spectrum disorders (ASD) or autism is a manifestation of developmental abnormalities of the brain (Landrigan 2010; Manning-Courtney et al 2003)
The median 2D:4D ratio for the left hand was comparatively lower for the ASD group when compared to that of the typically developing (TD) group (Table 1)
This study shows an association between a lowered 2D:4D ratio of the left hand and ASD diagnosis in ASD males
Summary
Autism spectrum disorders (ASD) or autism is a manifestation of developmental abnormalities of the brain (Landrigan 2010; Manning-Courtney et al 2003). Advanced parental age (maternal and paternal), abnormal gestational age (pre-term or post-term infant), low birth weight of the infant and the mode of delivery of the infant by caesarean section (CS) were among suggested risk factors for ASD (Curran et al 2015; Karimi et al 2017; Parner et al 2012) Both genetic and environmental factors may interact to influence the manifestation of the disorder (Tordjman et al 2014). Once validated in a larger sample size, a lowered median 2D:4D ratio on the left hand may be a potential tool to complement ASD diagnosis for males in our study population. Reduced asymmetry between the average 2D:4D ratio of left and right hands observed in ASD males only (not in ASD females) suggests the importance of considering gender-specific biomarkers for ASD diagnosis
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