The prevalence of autism spectrum disorder continues to increase worldwide, and diagnostic techniques and/or technologies are being developed to identify the disorder using biomarkers. Most biomarkers being studied do not address the differential diagnostic complexities that could arise from autism being caused by a mutation that may cause a different neurodevelopmental disorder (e.g., intellectual disability) in another individual. The purpose of this study was to develop a differential diagnostic method in which the same causative mutation leads to autism in one patient but intellectual disability in the other, thereby validating the feasibility of neonatal nitric oxide as a biomarker for the differential diagnosis of autism. Real-time bio-electroanalytical experiments were conducted using a porphyrinic modified carbon fiber-based nanosensor on induced pluripotent stem cells derived from an autism patient, a patient with intellectual disability, and a healthy individual to compare the levels of nascent nitric oxide among the samples. The choice of disease model cell lines was based on two factors: a) they must have the same causative mutation, but b) they should have different neuropsychiatric diagnoses. The healthy control cell line had to be unrelated to the disease cell lines with no neuropsychiatric diagnosis for any neurodevelopmental or neurodegenerative disorder. Both autistic and intellectual disability patients had a rare de novo mutation (E198K) in the B56δ β-subunit of the protein phosphatase 2 A enzyme. An autistic individual may produce approximately half the amount (6 nM) of nitric oxide produced by an intellectual disability patient (11 nM) but approximately ten times less than that produced by a healthy individual (65 nM). Despite overlapping etiologies and symptomatic similarities between autism and other neurodevelopmental disorders, real-time bio-electrochemical analysis of newly generated nitric oxide produced by induced pluripotent stem cells using carbon fiber-based porphyrinic nanosensors can still serve as a biomarker for the diagnosis and differential diagnosis of autism.
Khan et al. (Sun,) studied this question.