Validatie-onderzoek van het Nederlands Interview ten behoeve van Diagnostiek Autismespectrumstoornis bij volwassenen (NIDA)

Rationale: Autism spectrum disorder (ASD) in adults is an important clinical entity, for which there are several diagnostic instruments available. Guidelines on diagnosis of adults on ASD cannot give a best available suggestion for diagnostic assessment of an adult with possible autism, because of insufficient evidence for any specific formal assessment tool for ASD in adults.



Objective: The aim of the study is the psychometric evaluation of one of the diagnostic instruments for ASD in Dutch, which is the NIDA (Nederlands Interview ten behoeve van Autismespectrumstoornis bij volwassenen - Netherlands Interview for Diagnostic assessment of Autism spectrum disorder in adults). We will assess the reliability and validity of the NIDA by measuring its interrater reliability, convergent and discriminant validity (sensitivity, specificity) in a Dutch-speaking sample in the Netherlands.



Study design: A cross-sectional validation study design, with multiple groups: ASD, Personality Disorders (PD), and non-clinical comparison group (COM).



Study population: Male adult individuals (age ≥ 18 years) with ASD who were clinically diagnosed by a multidisciplinary team of psychologists and a psychiatrist in the (recent) past, and male adult individuals (age ≥ 18 years) with a PD who were assessed with the Structural Clinical Interview for DSM-IV (SCID-II) or DSM-5 Personality Disorders (SCID-5-PD), and male non-ASD and non-PD adult individuals (age ≥ 18 years; COM). Participants with ASD will be recruited from an expertise centre for autism. Participants with PD will be recruited from an outpatient psychiatric clinic in Rotterdam. COM participants will be recruited by advertisements and flyers. The study requires 90 participants (30 with ASD, 30 with PD and 30 COM). None of the participants will have an intellectual disability.



Procedure: Administering NIDA, ADOS, SCID-5-PD, and SCID-5-CV.



Main study parameters: The main study parameters are the sum and item scores of the 8 questions for current functioning on the NIDA.

We hypothesize that the NIDA is a reliable instrument and that individuals with a clinically diagnosed autistic disorder (AD; DSM-IV) or Asperger’s Disorder (AS; DSM-IV) and/or ASD (DSM-5) report more ASD features (according to the DSM-5) with the NIDA compared to those with a personality disorder (PD) and without AD/AS/ASD (no DSM-IV AD or AS classification and/or no DSM-5 ASD classification) and to those without PD and without AD/AS/ASD.

one moment per participant

To decide if a person can or can not participate in one of the three groups, a questionnaire for general information about primary diagnosis, age, education, marital status etc. and the SCID-5-SPQ (First et al. 2016a), the self-report screening tool for PDs will be assessed. When eligible for one of the three groups according this assessment, each participant will be once interviewed by a psychologist and once interviewed and observed by two other psychologists, all three qualified for diagnostic assessments. The NIDA, ADOS, SCID-5-PD interview and Structured Clinical Interview for DSM-5® Disorders-Clinician Version (SCID-5-CV; First et al. 2016b) will be administered to all participants (n = 90). All interviewers and observers are well trained and educated in at least ASD in adults, and in the NIDA by the study author, in the ADOS by ADOS-specialized trainers, and/or in the SCID by a SCID-specialized trainer. The interviewers and observers will be blind for diagnostic group and will not be permitted to obtain other sources of information to ensure that the final DSM-classification ASD for current functioning will be based only on the result of the NIDA.

To establish the interrater reliability of the NIDA, two psychologists jointly will assess 90 participants (30 with ASD, and 30 with PD without ASD, and 30 COM). One will perform the interview, the second will observe, and both will independently evaluate the participant according to this interview.

To establish convergent validity (sensitivity and specificity) scores on the NIDA and the ADOS will be compared for three groups of participants (ASD > PD without ASD > COM), and scores on the NIDA will be compared to the clinically assessed DSM-IV or DSM 5 ASD diagnosis. The order of NIDA and ADOS will be counterbalanced across participants, and will be administered by the same psychologists: one performs and the second observes. Both psychologists judge separately the social interaction style of the participant by indicating the most prominent style of making contact (i.e., aloof, passive, active-but-odd, over-formal).

To establish discriminant validity we compare the scores on the NIDA between three groups of participants (ASD > PD without ASD > COM). A third psychologist assesses PDs with the SCID-5-PD interview, and DSM-5 disorders with the SCID-5-CV in all three groups.