Comparing a Computerized Digit Symbol Test to a Pen-and-Paper Classic.

Background and hypothesis: Processing speed dysfunction is a core feature of psychosis and predictive of conversion in individuals at clinical high risk (CHR) for psychosis. Although traditionally measured with pen-and-paper tasks, computerized digit symbol tasks are needed to meet the increasing demand for remote assessments. Therefore we: (1) assessed the relationship between traditional and computerized processing speed measurements; (2) compared effect sizes of impairment for progressive and persistent subgroups of CHR individuals on these tasks; and (3) explored causes contributing to task performance differences.

Study design: Participants included 92 CHR individuals and 60 healthy controls who completed clinical interviews, the Brief Assessment of Cognition in Schizophrenia Symbol Coding test, the computerized TestMyBrain Digit Symbol Matching Test, a finger-tapping task, and a self-reported motor abilities measure. Correlations, Hedges' g, and linear models were utilized, respectively, to achieve the above aims.

Study results: Task performance was strongly correlated (r = 0.505). A similar degree of impairment was seen between progressive (g = -0.541) and persistent (g = -0.417) groups on the paper version. The computerized task uniquely identified impairment for progressive individuals (g = -477), as the persistent group performed similarly to controls (g = -0.184). Motor abilities were related to the computerized version, but the paper version was more related to symptoms and psychosis risk level.

Conclusions: The paper symbol coding task measures impairment throughout the CHR state, while the computerized version only identifies impairment in those with worsening symptomatology. These results may be reflective of sensitivity differences, an artifact of existing subgroups, or evidence of mechanistic differences.