Auditory Test of Processing Speed: Preliminary validation of a smartphone-based test of mental speed

Background: The Symbol Digit Modalities Test (SDMT) is a gold-standard measure of cognitive efficiency and processing speed for people with multiple sclerosis (PwMS) but relies on vision and oculomotor function. Objectives: To develop and validate a new processing speed test with minimal memory involvement and no eye function requirements. Methods: We created an Auditory Test of Processing Speed (ATOPS). A total of 122 PwMS, of whom 33 were severely disabled (median Expanded Disability Status Scale 8.0) and 37 healthy volunteers (HVs), were enrolled. We assessed sensitivity to discriminate MS participants from HVs, convergent validity between ATOPS and SDMT, sensitivity to discriminate between cognitively impaired (CI) and cognitively preserved (CP) MS participants, and correlations with MS pathology (overall brain lesion burden). Acceptability was examined with completion rates and participant ratings of ATOPS. Results: ATOPS discriminated PwMS from HVs (d = 0.739–0.856), correlated with SDMT (|r| = 0.528–0.587), discriminated between CI and CP PwMS (d = 0.623–0.776), and correlated with lesion burden (r = 0.332–0.436). All groups indicated high favorability of ATOPS and severely disabled MS patients could be assessed by ATOPS more frequently than by SDMT (100% vs. 72.4% completion). Conclusions: ATOPS is a novel, accessible, and acceptable cognitive processing speed test that may be useful in clinical and/or research settings.