Existing multiple sclerosis (MS) Patient Reported Outcome (PRO) instruments do not adequately capture ADLs. Previous qualitative research led to the development of the  IADL 30- and CADL 21- item sets.

718 MS patients enrolled in a study using the previously validated MS performance test (MSPT) for digital assessment of neuro-performance and PROs were included in the two-step cross-sectional psychometric evaluation. Step-1: identifying the best items using Rasch Measurement Theory (RMT) methods; targeting; item fit; response thresholds; reliability. In Step-2, the refined IADL and CADL item-sets were analyzed using Classical Test Theory (CTT) methods; data completeness; targeting; scaling assumptions; reliability; convergent validity; and known-groups validity as compared with neuro-performance metrics including the patient disease disability steps (PDDS) of self-report disability and number of relapses in the past year.

The sample comprised 75% women (mean age 49; SD 12); of mild: 54%, moderate: 39% and severe: 7% self-reported (PDDS) disability. Step-1 RMT led to the removal of 9 items. The refined IADL 23- and CADL 19- item sets showed good targeting coverage (86% & 84%), good overall fit, response thresholds for >97% and >93% of items and reliability (0.92 & 0.93). Step-2 CTT supported the RMT findings (i.e., good data completeness, targeting and scaling assumptions and high reliability (0.94 & 0.96). Convergent validity was supported, including correlations between the IADL (0.30 – 0.49) and CADL (0.17 – 0.49) with Neuro-QoL scales. IADL discriminated between PDDS groups (F=45.64, p<0.001) and IADL and CADL between relapses number (F=7.33, p<0.001, F=6.93, p<0.001, respectively).

IADL and CADL are promising, reliable and valid PRO instruments for use; particularly in capturing ADLs relevant in early MS (high-functioning patients). Future work includes establishing sensitivity to clinical change.