Development and psychometric validation of the Brief Intellectual Disability Scale for use in low–health resource, high-burden countries

Abstract

ObjectiveTo develop and validate a concise, parent-completed Brief Intellectual Disability Scale (BIDS) for children in low–disability resource and high–disability care burden countries. Study Design and SettingIn this prospective cross-sectional study of 124 children recruited from a facility for intellectual disability (ID), the newly developed BIDS as the measure for validation as well as for the gold standard and convergent and divergent validities was administered by independent raters. Tests for diagnostic accuracy, reproducibility, and validity were conducted at the item and scale levels. ResultsThe BIDS scores of ≥5 (sensitivity [Sn]=71.43%, specificity [Sp]=80.95%) and ≥11 (Sn=4.29%, Sp=100%), with area under the curve of 0.79, are suggested, respectively, for screening and diagnostic use in Indian populations. The inter-rater reliability (intra-class correlation coefficient [ICC]=0.96) and test–retest reliability at 4 weeks (ICC=0.95) for BIDS are strong. Besides the adequate face and content validities, BIDS demonstrates good internal consistency (Cronbach α=0.80) and item-total correlation. There is moderate convergent validity with Binet–Kamat Test of Intelligence or Gesell's Developmental Schedule (r=−0.66, P=0.001) as well as with adaptive behavior measure of Vineland Social Maturity Scale (r=−0.52, P=0.001) and low divergent validity with the subscales of Attention Deficit Disorder with Hyperactivity: Comprehensive Teacher Rating Scale (r=−0.11, P=0.7; r=0.18, P=0.5; r=0.13, P=0.6; r=0.08, P=0.7). An exploratory factor analysis demonstrated a three-factor structure, explaining 60% of variance. ConclusionThe BIDS shows promise as a psychometrically adequate, yet brief measure for identifying ID in countries with low disability care resources and high disability-related burden.