We conducted a cross-sectional study on 80 relapsing-remitting MS (RRMS) patients admitted to a specialized MS clinic between Jun 2021 to Nov 2021 and a control group consisting of age and gender-matched 60 healthy individuals who were admitted during the same period. Inclusion criteria are as follows:
1. Age between 18-50.
2. Clinically definite MS, according to the McDonald criteria(29)
3. Expanded Disability Status Scale (EDSS) ≤ 3.5.
Patients or control were excluded if they had a history of psychiatric disorders, MS relapse, and received corticosteroids or changes to the psychoactive medications within the previous month.
Study assessment
Integrated Visual and Auditory Continuous Performance Test (IVA-CPT): IVA-CPT (30) integrates inattention and impulsivity in visual and auditory modalities with 22 subscales, thus, incorporating four continuous performance tests (CPTs). It has also been used to assess attention and self-control across various neuropsychiatric conditions (18).
The test is designed in a boring way to assess impulsivity and inattention by errors of commission and omission, respectively. The test can be used for all patients above five years old. The Auditory Response Control Quotient (ARCQ) and the Visual Response Control Quotient (VRCQ) are based on equal weights of Prudence (impulsivity and response inhibition), Consistency (reliability of response time and staying on task), and Stamina (sustained attention and effort over time). The Auditory Attention Quotient (AAQ) and Visual Attention Quotient (VAQ) are based on equal rates of Vigilance (inattention), Focus (speed of mental processing), and Speed (reaction time) (31).
This IVA-2 Standard Report requires the test to be administered in accordance with the specified test guidelines under the supervision of a licensed health care professional who is qualified in the use and interpretation of psychological tests. The test is not to be used as a standalone diagnostic instrument. By itself, it does not identify the presence or absence of any clinical diagnosis. The function of the IVA-2 CPT is to aid examiners in making their diagnosis as part of a comprehensive evaluation of clients who present with ADHD-type symptoms. The relevant strengths and weaknesses for each of the Attention and Response Control Global Scales will be reviewed (32).
Hospital Anxiety and Depression scales: To assess anxiety and depression, we used the Persian validated Hospital Anxiety and Depression scales (HADS)(33). It consists of fourteen items that evaluate several aspects. Seven of the items are anxiety-related, and seven are depression-related. Each item on the questionnaire is scored from 0 to 3, which means a person could achieve between 0 and 21 for anxiety or depression. The patients with scores higher than 11 are considered depressed, anxious, or both (34).
Fatigue Severity Scale (FSS): For evaluating fatigue in the patients, we used FSS (35). It can assess daily fatigue in MS patients, consisting of nine items. Three questions are related to the psychosocial activities, three are about exercise, and the rest are more general questions about fatigue (36). FSS scores are the mean (1–7) or the sum of the item scores (9–63), with lower scores indicating less fatigue. Having a Fatigue Severity Scale score of less than 4, between 4 and 5, and more than five is considered mild, moderate, and severe fatigue, respectively(37).
Statistical analysis
Statistical analyses were performed using SPSS version 22.0 (SPSS, Inc., Chicago, IL, USA). To evaluate normal data distributions, Kolmogorov–Smirnov test was used. Chi-square and independent t-test were applied to analyze categorical and numerical data. Group differences (in MS and HCs) for each neuropsychological task were compared using an independent t-test. To control the covariate (confounding variable) statistically, we calculated the adjusted mean in all the study groups using one-way ANCOVA (analysis of covariance). The continuous variables, such as the fatigue score that had a significant relationship with the dependent variable, but no relationship with the independent variable, were considered covariate invariance analysis. In addition, multiple linear regression analysis was performed to explore the association between full-scale attention quotient (FSAQ) and full-scale response control quotient (FSRCQ) with MS characteristics (i.e., duration, Medication, HADS, and FSS). All statistical tests and final regression models were set based on a significant level of less than 0.05.