ABBA Letter Alternation: A telehealth inspired measure of executive functioning/inhibitory control.

Objective: To introduce ABBA Letter Alternation (ABBA) as a computerized measure of response inhibition/response alternation developed for telehealth following restrictions of in-person testing due to COVID-19. ABBA consists of two PowerPoint-administered trials: Letter Reading of 25 capital As or Bs individually presented, and Letter Alternation with instructions to say the opposite letter to what is presented. Method: We obtained initial normative ABBA performance from 899 healthy research volunteers participating in the Emory Healthy Brain Study (EHBS) with Montreal Cognitive Assessment (MoCA) scores 24/30 and higher. Cutpoints derived from the EHBS sample were applied to a series of 32 Parkinson disease (PD) patients being evaluated for deep brain stimulation to provide preliminary clinical validation. Trail Making B (TMT B) was also examined in both groups. Results: 775 (86.2%) EHBS participants made 0-1 ABBA Letter Alternation errors, 58 (6.5%) EHBS participants had 2 ABBA alternation errors, and 66 (7.3%) made 3+ errors. Applying these thresholds to PD patients, 22 (68.8%) made 0-1 alternation errors, 3 PD (9.4%) patients made 2 errors, and 7 PD subjects (21.8%) made 3+ errors, which significantly differed in frequency from the EHBS group (χ²=9.8, p=.007). EHBS vs. PD differed on MoCA, a medium effect (p<.00001; η²=.076), and on TMT B (p<.00001; η²=.158), which is considered a large effect. Conclusion: These results provide initial support for ABBA Letter Alternation as a response inhibition/response alternation. Application in larger clinical samples, in both telehealth and face-to-face settings, will be needed to more fully establish ABBA's clinical utility.