AbilityScore: Development and Preliminary Psychometric Characterization of a Standardized Composite Index for Quantifying Child Developmental Readiness

Background: Since the late nineteenth century, developmental assessment has relied on a series of siloed instruments rather than a single developmental score. A child assessed with ADOS-2, Vineland and Bayley receives three separate reports on three incompatible scales, leaving families and clinicians without a unified picture of progress.

Objective: To describe the architecture, computation methodology, and preliminary psychometric evidence for AbilityScore, a standardized composite developmental index (0–1000) that quantifies observed functional developmental performance relative to age-normed expectations in multiple validated constructs.

Methods: AbilityScore synthesizes the clinical essence of 25 internationally validated assessments into a single metric, mapping 339 skills across 148 abilities through structured clinical observations. The scoring algorithm uses a Skill Index (60%) and Ability Index (40%) weighted composite with age-gender normalization. Seven domain-specific Readiness Indexes (Speech, Motor, Behaviour, Cognitive, School, Self-Sufficiency, Mainstream) provide multidimensional profiling. Preliminary psychometric evidence comes from operational data from approximately 18.6 million therapy sessions spanning more than 70 centers, 4 Indian states, 16 languages, and 28 diagnostic categories.

Results: Operational data show inter-rater reliability r = 0.91 (p < 0.001), intraclass correlation coefficient ICC = 0.88 (95% CI 0.84–0.91), mean absolute percentage error MAPE = 6.7%, and bias variance ratio ≤ 1.05. These real-world scoring consistency metrics from routine operations across more than 70 centers provide a robust operational foundation for the formal validation study now in planning, but do not substitute for controlled psychometric validation.

Conclusions: AbilityScore is a scientifically structured, WHO ICF-aligned composite index for developmental measurement. Formal concurrent validity testing against Vineland-3, CARS-2, and Bayley-4, along with test-retest reliability studies, are now in planning (BHCL-VAL-2026-001). This monograph documents the instrument in sufficient detail to support the upcoming validation studies, regulatory submissions, and clinical use.