Reliable Change Indices and Standardized Regression Norms for the Hungarian version of the BICAMS questionnaire

Cognitive impairment (CI) is a significant burden for patients with multiple sclerosis (MS). However crucial its assessment is, longitudinal measurement of cognitive performance is susceptible to learning effect, making the results of repeated evaluations difficult to interpret. Reliable change index (RCI) and standardized regression based norms (SRB) are accepted statistical methods to assess the reliability of a difference score between two observations. Thus, our aims were to provide RCIs and SRBs for all three subtests of the Brief International Cognitive Assessment for MS (BICAMS) battery and to measure the prevalence of true cognitive worsening and improvement.

We retrospectively evaluated the first interim analysis data of the longitudinal follow-up or our BICAMS prevalence study-cohort after 1-year. We analyzed the data of 242 MS patients.

We calculated both the RCIs and the SRBs for all three subtests of the BICAMS battery. According to the RCI, 5.4%, 6.9% and 14.6% worsened while 12.3%, 34.3% and 10.6% improved on the SDMT, BVMT-R and CVLT-II respectively. In case of SRB method, 3.8%, 8.3% and 19.7% worsened while 3.8%, 7.6% and 0.0% improved. The κ values revealed a mild-to-moderate agreement (κ=0.391-0.540; p<0.001). In case of the BVMT-R and the CVLT-II assessments the baseline scores influenced this outcome significantly (BVMT-R: OR: 1.068; 90%CI: 1.001-1.138; CVLT-II: OR: 1.096; 90%CI: 1.041-1.153).

Comparing the methods, RCI seems to be better in cases with already established CI, while SRB, the more complex method, seemingly detects change better in cognitively intact patients.