Information Processing Speed Assessed with Letter Digit Substitution Test in Croatian Sample of Multiple Sclerosis Patients

Abstract

Cognitive impairment is a common complaint in people with multiple sclerosis (pwMS). The study objective was to determine the psychometric properties of the letter digit substitution test (LDST) that measures information processing speed and to investigate the impact of relevant predictors of LDST achievement in pwMS. The design was cross-sectional. The study included 87 pwMS and 154 control subjects. The validity of LDST was examined, and a hierarchical regression model was used to explore relevant predictors of LDST success. The LDST had excellent construct validity, as expressed by differences between pwMS and control subjects. Convergent validity of the LDST was supported by a significant moderate correlation with the expanded disability status scale (EDSS) (ρ = −0.36; p < 0.05) and a significantly strong correlation with the multiple sclerosis impact scale (MSIS-29) physical subscale (r = −0.64; p < 0.01). The LDTS score well differentiated the pwMS considering age, education, EDSS, disease duration, comorbidity, and medication therapy. Using the LDST as a criterion variable in pwMS results showed consistent evidence for the age, education, and EDSS impact on LDST performance. The best cut-off score of ≤35 discriminated the control and MS group. LDST proved to be a valid test for assessing information processing speed in pwMS.

Psychometric Properties of the Pittsburgh Sleep Quality Index (PSQI) in Patients with Multiple Sclerosis: Factor Structure, Reliability, Correlates, and Discrimination

“…It also adds to the knowledge about PSQI in general by testing the models presented in previous reviews [ 24 , 26 ], including a new model of the bifactor structure, as well as exploring the measurement invariance between control subjects and pwMS. It would be recommended for future studies investigating sleep quality in pwMS to manage demographic, socioeconomic status, habits (i.e., smoking), physical activity, fatigue, anxiety, depression, quality of life, as well as cognitive aspects [ 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 ].…”

Working Memory Phenotypes in Early Multiple Sclerosis: Appraisal of Phenotype Frequency, Progression and Test Sensitivity

“…Thus, the 188.89 ms slowing in visual–spatial response time found in this study is reasonably interpreted as abnormal and the consequence of MS disease. Inclusion of other measures of processing speed, such as the newly validated Letter Digit Substitution Test in MS, may help to elucidate these changes [ 70 ]. Finally, the inclusion of VEP and AEP investigations would have allowed determination of whether these changes are related to and/or impact the type of WM subcomponents impacted.…”

Editorial of Special Issue “Multiple Sclerosis: From Diagnostic Biomarkers to Imaging and Clinical Predictors”

“…The manuscript by Jerković et al validated a slightly adapted cognitive processing speed test called the letter digit substitution test (LDST) [ 2 ]. When compared to the current gold standard of the Symbol Digit Modalities Test (SDMT), LDST replaces the symbols with randomized letters of the alphabet and measures the processing speed over 60 s. An example of the LSDT can be directly accessed through the Supplementary Material of their manuscript [ 2 ].…”

“…The manuscript by Jerković et al validated a slightly adapted cognitive processing speed test called the letter digit substitution test (LDST) [ 2 ]. When compared to the current gold standard of the Symbol Digit Modalities Test (SDMT), LDST replaces the symbols with randomized letters of the alphabet and measures the processing speed over 60 s. An example of the LSDT can be directly accessed through the Supplementary Material of their manuscript [ 2 ]. Using LSDT data acquired in 196 healthy controls and 87 MS patents, the Authors determined that 35 points (AUC 0.698 and 95% CI of 0.677–0.718) would represent the optimal diagnostic cut-off point that could differentiate both groups [ 2 ].…”

“…When compared to the current gold standard of the Symbol Digit Modalities Test (SDMT), LDST replaces the symbols with randomized letters of the alphabet and measures the processing speed over 60 s. An example of the LSDT can be directly accessed through the Supplementary Material of their manuscript [ 2 ]. Using LSDT data acquired in 196 healthy controls and 87 MS patents, the Authors determined that 35 points (AUC 0.698 and 95% CI of 0.677–0.718) would represent the optimal diagnostic cut-off point that could differentiate both groups [ 2 ]. The LDST demonstrated concurrent and divergent validity when compared to the previously validated MS impact scale (MSIS-29) and the routinely utilized Expanded Disability Status Scale (EDSS).…”