title: Adult Autism Subthreshold Spectrum (AdAS Spectrum): Validation of a questionnaire investigating subthreshold autism spectrum.
abstract: Increasing literature has shown the usefulness of a dimensional approach to autism. The present study aimed to determine the psychometric properties of the Adult Autism Subthreshold Spectrum (AdAS Spectrum), a new questionnaire specifically tailored to assess subthreshold forms of autism spectrum disorder (ASD) in adulthood.
  
  
  
  102 adults endorsing at least one DSM-5 symptom criterion for ASD (ASDc), 143 adults diagnosed with a feeding and eating disorder (FED), and 160 subjects with no mental disorders (CTL), were recruited from 7 Italian University Departments of Psychiatry and administered the following: SCID-5, Autism-Spectrum Quotient (AQ), Ritvo Autism and Asperger Diagnostic Scale 14-item version (RAADS-14), and AdAS Spectrum.
  
  
  
  The AdAS Spectrum demonstrated excellent internal consistency for the total score (Kuder-Richardson's coefficient=.964) as well as for five out of seven domains (all coefficients>.80) and sound test-retest reliability (ICC=.976). The total and domain AdAS Spectrum scores showed a moderate to strong (>.50) positive correlation with one another and with the AQ and RAADS-14 total scores. ASDc subjects reported significantly higher AdAS Spectrum total scores than both FED (p<.001) and CTL (p<.001), and significantly higher scores on the Childhood/adolescence, Verbal communication, Empathy, Inflexibility and adherence to routine, and Restricted interests and rumination domains (all p<.001) than FED, while on all domains compared to CTL. CTL displayed significantly lower total and domain scores than FED (all p<.001). A significant effect of gender emerged for the Hyper- and hyporeactivity to sensory input domain, with women showing higher scores than men (p=.003). A Diagnosis* Gender interaction was also found for the Verbal communication (p=.019) and Empathy (p=.023) domains. When splitting the ASDc in subjects with one symptom criterion (ASD1) and those with a ASD, and the FED in subjects with no ASD symptom criteria (FED0) and those with one ASD symptom criterion (FED1),a gradient of severity in AdAS Spectrum scores from CTL subjects to ASD patients, across FED0, ASD1, FED1was shown.
  
  
  
  The AdAS Spectrum showed excellent internal consistency and test-retest reliability and strong convergent validity with alternative dimensional measures of ASD. The questionnaire performed differently among the three diagnostic groups and enlightened some significant effects of gender in the expression of autistic traits.
authors.affiliation: Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy.
authors.forename: L
authors.initials: L
authors.lastname: Dell'Osso
authors.affiliation: Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy.
authors.forename: C
authors.initials: C
authors.lastname: Gesi
authors.affiliation: Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy.
authors.forename: E
authors.initials: E
authors.lastname: Massimetti
authors.affiliation: Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy.
authors.forename: I M
authors.initials: IM
authors.lastname: Cremone
authors.affiliation: Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Barbuti
authors.affiliation: Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Maccariello
authors.affiliation: Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy.
authors.forename: I
authors.initials: I
authors.lastname: Moroni
authors.affiliation: Department of Clinical and Experimental Sciences, University of Brescia, Brescia, Italy.
authors.forename: S
authors.initials: S
authors.lastname: Barlati
authors.affiliation: Department of Neuroscience, Psychology, Drug Research and Child Health, University of Florence, Florence, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Castellini
authors.affiliation: Department of Psychiatry, University of Naples SUN, Naples, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Luciano
authors.affiliation: Department of Mental Health and Department of Molecular Medicine, University of Siena, Siena, Italy.
authors.forename: L
authors.initials: L
authors.lastname: Bossini
authors.affiliation: Department of Brain and Behavioral Sciences, University of Pavia, Pavia, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Rocchetti
authors.affiliation: Department of Clinical and Molecular Biomedicine, University of Catania, Catania, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Signorelli
authors.affiliation: Department of Clinical and Molecular Biomedicine, University of Catania, Catania, Italy.
authors.forename: E
authors.initials: E
authors.lastname: Aguglia
authors.affiliation: Department of Mental Health and Department of Molecular Medicine, University of Siena, Siena, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Fagiolini
authors.affiliation: Department of Brain and Behavioral Sciences, University of Pavia, Pavia, Italy.
authors.forename: P
authors.initials: P
authors.lastname: Politi
authors.affiliation: Department of Neuroscience, Psychology, Drug Research and Child Health, University of Florence, Florence, Italy.
authors.forename: V
authors.initials: V
authors.lastname: Ricca
authors.affiliation: Department of Clinical and Experimental Sciences, University of Brescia, Brescia, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Vita
authors.affiliation: Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy. Electronic address: claudia.carmassi@unipi.it.
authors.forename: C
authors.initials: C
authors.lastname: Carmassi
authors.affiliation: Department of Psychiatry, University of Naples SUN, Naples, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Maj
mesh_terms: D000293:Adolescent; D000328:Adult; D000067877:Autism Spectrum Disorder / Q000175:diagnosis*; D001321:Autistic Disorder / Q000175:diagnosis*; D016022:Case-Control Studies; D001068:Feeding and Eating Disorders / Q000175:diagnosis; D005260:Female; D006801:Humans; D008297:Male; D062706:Prodromal Symptoms; D011594:Psychometrics; D015203:Reproducibility of Results; D011795:Surveys and Questionnaires; D055815:Young Adult