Chapter 7 162 patients with the cohort of the study on the MoCA. Even though it is a missed opportunity from the perspective of the entire study, as presented in this dissertation, it is not necessarily the case for the individual study presented in Chapter 2. By choosing the MMSE, this specific study could be more accurately compared with the results of its sister studies with a different disease as a subject as well as with other publications. It should also be taken into consideration that at that time, the MoCA was not yet in general use and had not been validated in Dutch. In 2012 when the study was designed, the MMSE was still the ‘test to be used’ for rapid cognitive testing. 7.2.2 Methodological reflections of Section B and C: MoCA study population For the study of referred patients to geriatric psychiatry, we wanted to determine the criterion validation of the MoCA for MCI and mild dementia in this population. Although the MoCA has been validated many times, it has not been performed for this specific setting. It also turned out that the many validation studies that had already been conducted for various other settings were not very useful, not only because of the difference in setting, but also because many studies used healthy controls as a control group, that is, not patients but completely symptom-free volunteers. This introduces a case-control bias that can impact the outcome (Davis et al., 2013; Bossuyt et al., 2015), particularly, on the outcome of specificity. By comparing the study group to healthy controls who not only have no disorder under consideration but actually have no (subjective) complaints at all, and thus normally would not be referred for or assessed with a MoCA. Although one may envisage situations when this could occur in practice (e.g. screening the general population or knowing someone’s baseline functioning), the clinical reality is that this population will rarely be screened for cognitive symptoms in daily practice. In clinical practice, the test is more likely to be administered in the following settings: a population at higher risk with or without complaints, that is, screening, and a population with (different types of) complaints as well as (multiple) suspicions, that is, triaging. Therefore, the added value of a test is to be able to distinguish, in a group of patients at higher risk with or without subjective complaints, between those with and without objective cognitive complaints. This is better addressed by a cohort study, or, in other words, by assessing everyone from a certain population (with symptoms). Nevertheless, we, too, included a group of healthy volunteers in our study. This was done not only to show the extent of this effect (case-control bias), but also to better compare our results with other studies that chose this case-control design, similar to the original study of the MoCA (Nasreddine et al., 2005).
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