Equating norms between the ALS Cognitive Behavioral Screen (ALS-CBS™) and the Edinburgh Cognitive and Behavioural ALS Screen (ECAS) in non-demented ALS patients

Background: The present study aimed at deriving equating norms to estimate scores on the Edinburgh Cognitive and Behavioural ALS Screen (ECAS) based on those on the ALS Cognitive Behavioral Screen (ALS-CBS™) in an Italian cohort of non-demented ALS patients. Methods: ALS-CBS™ and ECAS scores of 293 ALS patients without frontotemporal dementia were retrospectively retrieved. Concurrent validity of the ALS-CBS™ towards the ECAS was tested by covarying for demographics, disease duration and severity, presence of C9orf72 hexanucleotide repeat expansion and behavioural features. A linear-smoothing equipercentile equating (LSEE) model was employed to derive ALS-CBS™-to-ECAS cross-walks. Gaps in LSEE-based estimation were managed via a linear regression-based equating approach. Equivalence between empirical and derived ECAS scores was tested via a two-one-sided test (TOST) procedure for the dependent sample. Results: The ALS-CBS™ predicted the ECAS (β = 0.75), accounting for the vast majority of its variance (60% out of an R 2 = 0.71). Consistently, a strong, one-to-one linear association between ALS-CBS™ and ECAS scores was detected (r = 0.84; R 2 = 0.73). The LSEE was able to estimate conversions for the full range of the ALS-CBS™, except for raw scores equal to 1 and 6 – for whom a linear equating-based equation was derived. Empirical ECAS scores were equivalent to those derived with both methods. Discussion: Italian practitioners and researchers have been herewith provided with valid, straightforward cross-walks to estimate the ECAS based on ALS-CBS™ scores in non-demented ALS patients. Conversions herewith provided will help avoid cross-sectional/longitudinal inconsistencies in test adoption within research, and possibly clinical, settings.