INCLEN Diagnostic Tool for Autism Spectrum Disorder (INDT-ASD): development and validation.

OBJECTIVE To develop and validate INCLEN Diagnostic Tool for Autism Spectrum Disorder (INDT-ASD). DESIGN Diagnostic test evaluation by cross sectional design. SETTING Four tertiary pediatric neurology centers in Delhi and Thiruvanthapuram, India. METHODS Children aged 2-9 years were enrolled in the study. INDT-ASD and Childhood Autism Rating Scale (CARS) were administered in a randomly decided sequence by trained psychologist, followed by an expert evaluation by DSM-IV TR diagnostic criteria (gold standard). MAIN OUTCOME MEASURES Psychometric parameters of diagnostic accuracy, validity (construct, criterion and convergent) and internal consistency. RESULTS 154 children (110 boys, mean age 64.2 mo) were enrolled. The overall diagnostic accuracy (AUC=0.97, 95% CI 0.93, 0.99; P<0.001) and validity (sensitivity 98%, specificity 95%, positive predictive value 91%, negative predictive value 99%) of INDT-ASD for Autism spectrum disorder were high, taking expert diagnosis using DSM-IV-TR as gold standard. The concordance rate between the INDT-ASD and expert diagnosis for 'ASD group' was 82.52% [Cohen's k=0.89; 95% CI (0.82, 0.97); P=0.001]. The internal consistency of INDT-ASD was 0.96. The convergent validity with CARS (r = 0.73, P= 0.001) and divergent validity with Binet-Kamat Test of intelligence (r = -0.37; P=0.004) were significantly high. INDT-ASD has a 4-factor structure explaining 85.3% of the variance. CONCLUSIONS INDT-ASD has high diagnostic accuracy, adequate content validity, good internal consistency high criterion validity and high to moderate convergent validity and 4-factor construct validity for diagnosis of Autistm spectrum disorder.