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Validation of the Brief Assessment of Impaired Cognition and the Brief Assessment of Impaired Cognition Questionnaire for identification of mild cognitive impairment in a memory clinic setting

Objectives The aim of this study was to validate the Brief Assessment of Impaired Cognition (BASIC) and the Brief Assessment of Impaired Cognition Questionnaire (BASIC‐Q) for identification of mild cognitive impairment (MCI) in a memory clinic setting. Methods A total of 163 sociodemographically matched patients (MCI, n = 42, and dementia, n = 121) and 83 control participants were included in the study. Two instruments were validated: (a) BASIC, including the components self‐report, informant report, and two brief cognitive tests, and (b) BASIC‐Q, including the components self‐report, informant report, and orientation. BASIC can be administered in 5 minutes and BASIC‐Q in less than 5 minutes. Results A high discriminative validity for MCI vs control participants was found for both BASIC (sensitivity 0.86, specificity 0.89) and BASIC‐Q (sensitivity 0.88, specificity 0.88). In comparison, the MMSE had low sensitivity (0.61) and moderate specificity (0.72). All components of BASIC and BASIC‐Q contributed significantly to differentiate MCI from control participants. The components of BASIC and BASIC‐Q also contributed significantly to differentiate MCI from dementia, except for self‐report, which was identical in the two groups. Conclusions Both BASIC and BASIC‐Q are brief, valid, and effective instruments for identification of patients with possible MCI in a memory clinic setting. Further cross‐validation of the instruments in a general practice or primary care setting is needed.


| INTRODUCTION
Brief, accurate, and practical case-finding instruments are highly relevant for identification of mild cognitive impairment (MCI) in a clinical setting. MCI is clinically defined as a condition where the person is not cognitively intact, but without dementia, and with preserved basic activities of daily living. Historically, clinical criteria for MCI, focusing on memory impairment, were initially defined by Ronald Petersen, 1,2 but in 2004 a broader conception including both amnestic and nonamnestic MCI-subtypes was introduced 3,4 which has essentially been adopted by subsequent definitions and elaborations of MCI-criteria. [5][6][7] Estimates of the prevalence of MCI from epidemiological studies show considerable variation which may be attributed to differences in methodology and definitions of MCI, 8 but the majority of studies report a prevalence in the range of 12% to 18% in people aged 60 years or older. 9 In clinical samples, the prevalence is even higher.
Thus, in Danish memory clinics approximately 25% of newly referred patients are subsequently assigned a diagnosis of MCI. 10 In a clinical context, both the differentiation between normal ageing and MCI and the differentiation between MCI and mild dementia may be a challenge. Cognitive tests and brief test batteries [11][12][13][14][15] are often used for identification of dementia and MCI but the time needed for test administration (10 minutes or more) may be a disadvantage in a busy clinical setting, test performance may be influenced by sociodemographic variables such as education and age, [16][17][18][19][20][21][22][23] and some test items (such as Serial sevens in The Mini-Mental State Examination, MMSE, 11  whereas the rest performed less favourably. 25 Another systematic review identified more than 40 brief cognitive instruments for identification of amnestic MCI vs controls, of which the MoCA was the most comprehensively investigated. 26 Neuropsychological measures of immediate and delayed memory generally have acceptable accuracy for detection of MCI vs healthy controls, 27 and also seem to be accurate in predicting progression from MCI to dementia. 28 Neuropsychological assessment, however, is relatively time consuming and access to neuropsychological assessment may be limited in clinical practice. Consequently, there is a need for accurate, time-saving and nonconfrontational tools for identification of MCI in a clinical setting. We have previously developed and validated two new brief casefinding instruments in a Danish multicenter study: The Brief Assessment of Impaired Cognition (BASIC), 29 and the Brief Assessment of Impaired Cognition Questionnaire (BASIC-Q). 30 We found BASIC to be highly accurate in classifying dementia (sensitivity 0.98, specificity 0.95), while BASIC-Q, that is primarily intended for use in community settings, was highly accurate in classifying cognitive impairment (including dementia and MCI; sensitivity 0.92, specificity 0.97). Both instruments appear to be relatively unaffected by sociodemographic characteristics. 29,30 The aim of this study was to examine the ability of the BASIC and BASIC-Q to identify MCI in a memory clinic setting.

| METHODS
BASIC and BASIC-Q include identical self-report and informant report components, but BASIC additionally includes two brief cognitive tests: Supermarket Fluency, and Category Cued Memory Test, whereas BASIC-Q instead includes four orientation items (Table 1).
BASIC and BASIC-Q were inspired by existing, validated instruments 31-33 and includes elements from validated questionnaires. 34,35 According to interviews with patients and informants, BASIC and BASIC-Q are perceived as relevant and nonconfrontational. 29 A total BASIC score is obtained by summing the scores of four components into a composite score (range 0-25 points), whereas a total BASIC-Q score is obtained by summing the scores of three components into a composite score (range 0-20 points). If reliable informant report cannot be obtained, a pro-rated score estimate may be used in both instruments. Although BASIC and BASIC-Q are separate instruments intended for use in different settings, they were derived from the same preliminary instrument and were validated simultaneously in the Key points • The self-and informant report components of BASIC and BASIC-Q are equally valid measures of cognitive impairment early in the process of decline, but as dementia sets in, the validity of self-report becomes inferior to informant report, possibly reflecting loss of insight. In contrast, the validity of informant report seems to increase with the progression of cognitive impairment. same setting. In this study, we therefore present results for both instruments regarding identification of MCI.

| Participants
The study was carried out in accordance with the Code of Ethics of

| Procedure
The validation of BASIC and BASIC-Q for identification of MCI is based on further analysis of data from the primary validation of the two instruments, which was a prospective study in which patients were assessed prior to diagnosis. 29 In most cases, diagnosis was established 1 to 3 months later. At each site, the preliminary instrument was administered by trained nurses or physicians. Administration was standardized across memory clinics. Informants concurrently completed a brief informant report questionnaire. Control participants served as their own informants. Age, gender, and postsecondary education (type and approximate length of education exceeding compulsory education), were registered for all participants.

| Data analysis
The significance of group differences on continuous variables was determined using independent samples t-test. The significance of group differences in gender distribution was determined using the Pearson χ 2 test. Effect sizes were calculated as Hedges' g. 47 Effect sizes of 0.2 to 0.5 were considered small, >0.5 to 0.8 were considered moderate and >0.8 were considered large. Discriminative validity was assessed by calculating sensitivity, specificity and likelihood ratios using a clinical diagnosis of MCI as reference standard. The optimal balance between sensitivity and specificity for discrimination between groups was determined by Youden's J. 48 Receiver operating Brief Assessment of Impaired Cognition (BASIC) case-finding instrument and Brief Assessment of Impaired Cognition Questionnaire (BASIC-Q) BASIC Score range BASIC-Q Score range 1. Self-report 1. Self-report    Table 2). Significant differences were also present between the MCI and dementia group on BASIC, BASIC-Q and their components except for self-report where mean scores (3.7) were identical in the two groups.

| Discriminative validity
Using the AUC as a general index of discriminative validity, both BASIC (AUC = 0.95) and BASIC-Q (AUC = 0.94) were accurate in differentiating patients with MCI from control participants. In comparison, the MMSE had an AUC of 0.67 (Figure 2).  Table 3.
A cutoff score of 21/22 on BASIC provided optimal discrimination between the MCI and control group with high sensitivity (0.86) and specificity (0.89). This is in accordance with the score distribution for BASIC, as 81 of 83 control participants scored in the range of 22 to 25, whereas the majority of MCI participants scored below 21 (Figure 1). A roughly similar classification accuracy (sensitivity 0.88, specificity 0.88) was found for BASIC-Q at an optimal cutoff score of 17/18 (Table 3 and Figure S1).
By comparison, the MMSE had poor sensitivity (0.61) but moderate specificity (0.72) at an optimal cutoff score of 28/29, and negligible sensitivity (0.15) but maximum specificity (1.00) at the commonly applied cutoff score of 23/24 (Table 3 and Figure S2).  Table S2). Predictive validity estimates for a range of scores below and above the optimal cutoff at selected base rates of MCI are presented in Table S3. The data regarding the score distribution for MMSE indicate a ceiling effect in the MCI group ( Figure S2), whereas no ceiling effect appears to be present for BASIC (Figure 1) or BASIC-Q ( Figure S1).  35 According to a longitudinal study, both CFI versions were associated with cognitive decline during 4-year follow-up. But self-report appeared more accurate when the respondent was cognitively intact, whereas the accuracy of informant report improved concurrently with cognitive impairment. 35,57 In a Norwegian validation study, both versions of the CFI discriminated between people with dementia and those with either MCI, subjective cognitive impairment, or a reference group. 58 But again, the informant report version of CFI had better discriminatory power than the self-report version in the dementia stage.
Although the classification performance of BASIC and BASIC-Q for MCI is similar, we recommend the longer BASIC in clinical settings, as it provides more detailed information on cognitive functioning than BASIC-Q. Also, BASIC contains a larger proportion of "objective" measures of cognitive functioning compared to BASIC-Q, possibly preserving the validity of BASIC in situations where the patient lacks insight.
In the present sample, the optimal cutoff scores for separation of persons with MCI from control participants was 21/22 for BASIC and 17/18 for BASIC-Q. However, when evaluating the performance of an individual person, optimal group separation is not the focus of interest.
Instead, the probability of MCI vs the probability of being cognitively intact associated with a given performance is more relevant. We therefore present predictive validity estimates for different base rates of MCI (Table S3). In Danish memory, clinics approximately 25% of the patients referred for assessment are assigned an MCI diagnosis. 10 In this setting, both PPV (0.72) and NPV (0.95) seem acceptable.
But in a low base rate setting, for example, a general practice setting, PPV is attenuated (0.30) due to a higher proportion of false positive cases. For instance, in a 5% base rate setting a downwards adjustment of the BASIC cutoff score to 20/21 or even 19/20 may be considered in order to ensure an acceptable PPV. A high NPV is also desirable in a general practice setting, but this requirement appears easily met for BASIC and BASIC-Q as NPV for both instruments is in the 0.98 to 1.00 range depending on cutoff score.
The patients in this study were referred from general practice and undiagnosed at the time of assessment. As BASIC and BASIC-Q had no influence on subsequent clinical diagnosis, the risk of circular evidence was minimal. Among the limitations of the study is the relatively small MCI sample and the fact that we did not have access to neuropsychological assessment results or AD biomarker data as patients were examined at five different sites. Consequently, we were not able to perform independent verification of MCI-diagnoses or conduct a subtyping of MCI-cases based on neuropsychological profiles (eg, amnestic vs nonamnestic MCI) or biomarkers (eg, prodromal vs non-prodromal AD). A further limitation is the fact that data were collected exclusively in a memory clinic setting. Our clinical sample may be representative for persons referred from general practice at their first memory clinic admission, but not for a general practice or primary care setting. Future studies are needed to cross-validate BASIC and BASIC-Q in these settings.

| CONCLUSION
The results of this study indicate that both BASIC and BASIC-Q meet criteria for accurate, time-saving, and easy-to-use tools for identification of MCI in a memory clinic setting. Both instruments appear to be sensitive and specific for identification of MCI among persons referred from general practice for expert diagnostic evaluation. It must be emphasized, though, that neither instrument can substitute expert clinical evaluation. A diagnosis of MCI cannot be based solely on a brief case-finding instrument, but BASIC and BASIC-Q appear to be effective tools for identifying patients for whom further diagnostic assessment should be considered.