The Face-Symbol Test and the Symbol-Digit Test are not reliable surrogates for the Paced Auditory Serial Addition Test in multiple sclerosis

The Paced Auditory Serial Addition Test (PASAT) is the chosen task for cognitive assessment in the multiple sclerosis functional composite (MSFC) and a widely used task in neuropsychological studies of people with multiple sclerosis (MS), but is unpopular with patients. The Face-Symbol Test (FST) and Symbol-Digit Tests (SDT) are alternative methods of cognitive testing in MS, which are easily administered and patient-friendly. In order to evaluate the potential of the FST as a possible surrogate for the PASAT, we directly compared the FST to the PASAT and the SDT in a cohort of 50 MS patients with varying levels of disability. There was significant correlation between SDT and FST scores (Spearman’s rho 0.80, 95% CI 0.66 - 0.88), R2 65%, with moderate inter-test agreement (κ = 0.52). In contrast, SDT and FST scores were less predictive of PASAT scores. We concluded that neither the FST nor SDT are reliable surrogates for the PASAT.