Dispersion of cognitive performance test scores on the MATRICS Consensus Cognitive Battery: A different perspective

Objective: Persons with schizophrenia exhibit greater neurocognitive test score dispersion. Here, we seek to characterize dispersion on the Neurocognitive Composite subtests of the Measurement of Treatment Research to Improve Cognition in Schizophrena Consensus Cognitive Battery (MCCB) and determine the relative effects of different antipsychotic formulations on dispersion and mean performance. Method: In this post hoc analysis of the DREaM study (NCT02431702), which compared treatment with paliperidone palmitate (PP) long-acting injectable with oral antipsychotic (OAP) treatment over 18 months, dispersion in MCCB neurocognitive subtest performance was calculated for each participant by visit (test occasion). Results: Over 18 months, mean neurocognitive performance improved in a manner consistent with the expected effects of practice in both groups (p < 0.05); this improvement was observed during the first 9 months (PP: p < 0.05, OAP: p < 0.001), followed by stable performance over the second 9 months (PP: p = 0.821, OAP: p = 0.375). Rates of change did not differ between groups (treatment-by-visit interaction: p = 0.548). In contrast, analyses of dispersion focusing on contrasts between baselines and end points of the first and second 9 months revealed different patterns. Over the first 9 months, dispersion in both groups lessened to a similar extent. However, over the second 9 months, dispersion remained stable in the PP group, whereas neurocognitive performance became significantly more variable in the OAP group (p < 0.01). Conclusion: Dispersion of neurocognitive test scores provides a different index of cognitive change than that provided by composite scores. Long-term maintenance of therapeutic levels provided by PP over time may limit (relative to oral AP) the extent to which cognitive performance becomes more variable.