The individual MoCA domain scores demonstrated high factor loadings with standard neuropsychological measures purported to measure similar cognitive constructs, providing empirical validation for the construct validity of the MoCA domain classifications. These findings lend further support for the use of the MoCA as a brief screen of cognition that reflects similar constructs as those gleaned from a more comprehensive battery. Most notably, the memory domain from the MoCA demonstrated a strong association with standard neuropsychological measures of memory and of the individual MoCA domain scores demonstrated the strongest loading. This is of particular relevance to practitioners working with neurodegenerative disease populations, as individuals demonstrating poor memory performance on the MoCA are likely to also demonstrate memory impairment on more comprehensive neuropsychological testing, validating the utility of the MoCA as a memory screening tool. What remains unclear is whether similar impairment profiles emerge on the MoCA as those on more standard neuropsychological measures (e.g., retrieval vs. encoding deficits), which could further aid in refining differential diagnoses; this reflects an empirical question of interest and target of future study.
A significant advantage of the MoCA over other cognitive screening measures is the breadth of cognitive domain coverage beyond memory, which increases its clinical utility, particularly for detection of individuals presenting with nonamnestic cognitive changes. As shown by the present findings, performance on the MoCA is also sensitive to visuospatial ability and executive functioning, attention, as well as language and that the standard domain organization developed by the authors of the MoCA parallels that which is measured by more comprehensive assessment. One limitation of the present study is the long wait times between the administration of the MoCA and the full neuropsychological battery (e.g., up to 180 days). The time between MoCA and full neuropsychology testing is an organic factor of wait times for a neuropsychological evaluation at the time of data collection. Although there may be some progression of symptoms in the interim, we would expect the progression to manifest similarly within domains, so would likely not have an impact on our results.
Although most measures were clearly associated with a single construct, several measures demonstrated multiple associations. The most evenly distributed was the digit span sequencing score, a measure of verbal working memory that loaded on both the visuospatial/executive component (0.36) and the attention component (0.51), which is consistent with previous literature suggesting that working memory, particularly mental manipulation, requires both attention, as well as executive demands [22] and [23]. The MoCA language score was strongly associated with the attention component, as well as the language component, albeit to a lesser degree. Reviewing the items comprising the MoCA language score finds that 2 of 3 possible points are derived from a repetition task, which requires basic attention to complete and may account for the higher loading on attention. Similarly, the WAIS-IV similarities subtest, which requires verbal abstract reasoning and concept formation, showed a split-loading, associating strongly with the language component but also with the attention component. The switching trial of DKEFS trails was also associated with two components, including the visuospatial/executive component and the attention component, which may be attributable to the executive demands required to switch effectively, as well as the working memory demands required to maintain set.
Although the present study supports the construct validity of the MoCA when compared with more comprehensive neuropsychological measures, it does not evaluate the diagnostic sensitivity and specificity of the domain scores. In previous research, when the diagnostic sensitivity and specificity of the MoCA was compared with a full neuropsychological evaluation, the total MoCA score has been found to have high sensitivity but low specificity [5] and [7], which is to be expected given the broad sampling of cognitive constructs. Although poor specificity precludes use of the MoCA as a diagnostic tool, the high sensitivity reinforces the notion that the MoCA is a valuable screening tool that can be used to guide clinical decision making to help determine when more comprehensive neuropsychological testing would be beneficial.
As suggested in previous research, a score below the cutpoint warrants a full neuropsychological evaluation to better characterize the extent of cognitive impairment and more thoroughly evaluate an individual's cognitive pattern of performance. Because of the high correspondence between MoCA domain scores and standard neuropsychological measures, our results also suggest the MoCA can provide a qualitative understanding of an individual's performance on subdomains, even though the deficit may be highly specific. Furthermore, although our findings are suggestive of the utility of the MoCA to assess the overall cognitive profile of patients and future research may find that the cognitive profiles produced with the MoCA are diagnostically useful, clinical use of scores other than the total score has not been validated. Until such time, the MoCA remains an excellent tool for cognitive screenings, which have their place in many contexts. Comprehensive neuropsychological assessment, however, when and where available remains the preferred method for generating a more refined profile regarding cognitive functioning.