Influence of recruitment and participation bias in neuropsychological research among MS patients

Abstract

The potential influence of recruitment context in neuropsychological (NP) research is seldom addressed in the literature. Our experience with a previous large-scale study of MS cognitive impairment led us to speculate that referral questions and motivation bias significantly impact conclusions drawn from NP testing. We re-analyzed data from Benedict et al. (2006) and compared the results obtained across three groups of patients: paid research volunteers, clinical patients undergoing evaluation for routine monitoring of cognitive status, and clinical patients referred for diagnostic clarification, determination of disability benefits, and other more complex issues. Research volunteers were significantly younger and less frequently cognitively impaired compared to the clinical groups, greatly affecting prevalence estimates (45.6 to 65.6%). Significant correlations between depression and cognitive impairment were present only among the research volunteers. NP testing significantly predicted vocational outcomes in all groups. These results suggest that greater attention should be paid to the reasons patients agree to participate in NP testing. (JINS, 2008, 14, 494-498.)

Upper and Lower Extremity Motor Function and Cognitive Impairment in Multiple Sclerosis

“…Our study is limited is several ways, not the least of which is the retrospective, cross-sectional design preventing conclusions about cause and effect relationships between cognition and motor decline. We relied on data collected for other purposes from patients volunteering for research but also seeking clinical evaluation (Duquin, Parmenter, & Benedict, 2008), and some of the patients were taking medication that could conceivably impact cognitive function. The sample had a relatively low EDSS, and while the motor tasks were normally distributed, a greater degree of pathology in motor capacity may have resulted in more generalizable, and robust results.…”

The NEO-FFI in Multiple Sclerosis: Internal Consistency, Factorial Validity, and Correspondence Between Self and Informant Reports

“…The factorial validity analyses were not conducive to this approach because of sample size limitations and similarly we were unable to compare subgroups of self-informant agreement because only a subsample of subjects had informant ratings. Method of recruitment was examined as a potential moderator of psychometric properties because recent findings suggest that MS patients recruited through either research, routine clinical care, or clinical referral channels may show different response patterns on neuropsychological tests (Duquin, Parmenter, & Benedict, 2008). Demographic subgroups were defined as follows: men versus women, high school or less versus greater than high school education, and persons younger than the sample average age of 47 years versus those 47 years and older.…”

Subjective fatigue is not associated with cognitive impairment in multiple sclerosis: cross-sectional and longitudinal analysis

“…Finally, depression was assessed using the Beck Depression Index Fast Scale (BDIFS), which has also been found to be valid in the MS population [37]. These tests have well-established reliability and validity in separate retrospective studies [28] and in single cohort prospective research [11,13,38]. MS patients were classified as cognitively normal or cognitively impaired based on the diagnostic criteria iterated for the MACFIMS battery, which defines impairment on a single test as a z score <−1.5, and cognitive impairment as two or more NP test z scores <−1.5 [11].…”