Measurement invariance of neuropsychological tests in diverse older persons.

Neuropsychological assessment is a core component of the diagnostic process for Alzheimer’s disease (AD) and other dementias, and plays a major role in monitoring response to treatment. In the U.S., numbers of older adults of ethnic minority heritage are increasing in absolute terms and as a percentage of the total population. Although the general population over age 65 is projected to increase by 160% over the next 50 years, Hispanic older adults are projected to increase over 600% and African American older adults by 270% (Population Reference Bureau, 2000; U.S. Bureau of the Census and J.C. Day, 1993). As increasingly larger numbers of ethnic minorities seek evaluation and treatment of memory and other cognitive changes, comparability of meaning of neuropsychological test scores across diverse groups becomes particularly relevant. Concern about measurement equivalence or invariance arose in reference to the fairness of college admission tests (Meredith & Teresi, 2006). At issue was whether tests were biased towards the selection of one sub-population at the expense of another; and this led to development of methods to examine measurement equivalence among groups. Valid inferences about individual differences in attributes/abilities of persons from different groups cannot be made unless the attributes relate to observed test results in the same way in the different groups (Borsboom, 2006). This condition, known as measurement equivalence, essentially means that two persons from different groups who have the same true ability will achieve the same test score, and is a prerequisite for unbiased measurement (Meredith & Teresi, 2006; Vandenberg & Lance, 2000). In a factor analytic context, measurement equivalence is discussed under the label of factorial invariance and is evaluated by examining the relations between theoretical (latent) constructs (i.e. memory) and their manifest (observed) indicators (test scores from measures of memory). Psychological measurements are considered comparable when relations between test scores and factors defining latent constructs are equivalent across groups (Reise, Widaman, & Pugh, 1993). Without equivalent measurement, observed scores from diverse groups are expressed in different scales and are not directly comparable (Drasgow & Kanfer, 1985). For example, a score of 15 might be associated with higher ability in one group than in another, and so, would not have the same meaning for individuals from these two groups. Principal component analysis (PCA) was widely used in earlier studies to investigate measurement invariance; for example, to examine of the construct validity of intelligence tests across groups defined by race/ethnicity (e.g. Chastain & Joe, 1987; Kaufman, McLean, & Reynolds, 1991) and language (e.g. Drago, Daum, & Canavan, 1991; Gomez, Piedmont, & Fleming, 1992; Insua, 1983; Laicardi, Frustaci, & Lauriola, 1996; Orsini & Laicardi, 2000). PCA has limitations in evaluating measurement invariance (Borsboom, 2006), and more rigorous methods based on confirmatory factor analysis (CFA) have been recommended more recently for comparing the factor structure of cognitive tests and batteries across diverse groups (e.g. Geary & Whitworth, 1988; Gregoire, 2004; Pedraza, et al., 2005; Widaman & Reise, 1997). In CFA, the factor structure is specified a priori on the basis of previous research and/or theoretical considerations (McArdle, 1996). To test the dimensional equivalence across multiple, independent groups the a priori factor structure is fit to all groups simultaneously. Factor solutions shown to be identical across groups provide strong evidence of common dimensions underlying performance. This study examined the dimensional structure of a neuropsychological test battery designed to measure neuropsychologically relevant domains of cognition in linguistically and demographically diverse older adults. The Spanish and English Neuropsychological Assessment Scales (SENAS) has undergone extensive development as a battery of cognitive tests relevant to diseases of aging (Mungas, Reed, Crane, Haan, & Gonzalez, 2004; Mungas, Reed, Haan, & Gonzalez, 2005; Mungas, Reed, Marshall, & Gonzalez, 2000; Mungas, Reed, Tomaszewski Farias, & DeCarli, 2005). Here the dimensional structure of the SENAS was evaluated in groups of older African Americans, Caucasians, and English- and Spanish-speaking Hispanics. This study represents one component step in the ongoing construct validation of the SENAS and also addresses more general questions about the organization of cognition in older populations.