The sample comprised of outpatients receiving care at the Psychogeriatric Unit of the CHUS University Hospital (Santiago de Compostela, Spain). This publicly-funded service is covers a population of around 500,000 inhabitants residing in the area surrounding Santiago de Compostela. Patients over 65 years old were referred by general practitioners and other the Mental Health Services to receive specialized care by an multisciplinary team formed of two psychiatrists, a psychologist and a social worker.

Over the above RUDAS validation study, 97 patients who were administered the MMSE and RUDAS on the same day were recruited. Of note, 18 of the 115 subjects included in the original validation study were excluded since MMSE and RUDAS had not been administered at the same outpatient appointment. All the subjects were over 65 years and suffered from a variety of mental disorders, including frequent memory loss complaints. Informed consent was obtained from either the patients or their main carers. Patients with unconfirmed dementia at the initial assessment and those who were clinically unstable were also included.

Only patients with severe physical limitations (such as hemiparesia, severe hearing loss or blindness) were excluded. Participants consented to the test (or their relatives if the patient lacked capacity) and collaborated with the study procedure.

The RUDAS total scores range from 0 to 30, lower scores indicating more impaired cognition. In particular, six cognitive domains are assessed, including memory (up to four items from a grocery list to be recalled, each of which is scored from 0 to 2, hence 8/30), body orientation (up to 5 points over 30 from 8 items, i.e. over 5 correct items are rated 5 instead of 8), visuo-spatial praxis (which consists of drawing a cube, which can be evaluated from 0 to 3/30), motor praxis (by copying a hand exercise initially displayed by the examiner, which is rated up to 2/30), judgement (up to 4 points out of 30 can be given depending on the patient's answer to a question enquiring about how to cross the road, i.e. his/her road safety awareness) and language (namely, verbal fluency, by naming as many animals as possible within 1min, with a maximum of 8/30). Only the word “tea” from the grocery list was changed for “coffee”, which is more common in our region. The RUDAS was validated in a sample of outpatients seen at a Psychogeriatric Unit showing good psychometric properties and being easy to administer to, and well accepted by, interviewee.20,21

The MMSE version sued in this study had been validated in the Galician population22 as part of the diagnoses protocol of the Psychogeriatric Unit, which was an adaptation of the Portuguese validated version.23 This was decided due to the excessive literality of most of the Spanish versions and the bilingualism of Galician population, in which Spanish and the native language, which is rather similar to Portuguese, are equally used. This version ranges from 0 to 30 and it includes the ‘minus 7’ substractions and world spelling.

The RUDAS was administered by two medical students (RRR and JDLM) who were blind to the patient diagnosis. They were trained in the application of the instrument, including the support with written and audiovisual material provided by the authors. An expert clinician (RMA), who was blind to the results of the RUDAS, administered the MMSE as part of the service comprehensive diagnostic protocol which included several clinical interviews with the patient and their caregiver(s), with input from the multidisciplinary team in order to complete the diagnosis and organize the care plan. The assessment of the severity of dementia was measured by the Clinical Dementia Rating Scale (CDR)24 and the Reisberg's Global Deterioration Scale (GDS).25 A diagnosis of dementia was made according to the ICD-10 criteria. With regard to those with undiagnosed dementia at the initial assessment, it should be noted that, consistently with the psychogeriatric unit approach, these patients were followed up as part of the routine care (i.e., no special follow-up was delivered after the study inception).

Receiver operating characteristic (ROC) curve analysis compared the accuracy of the RUDAS and the MMSE regarding the diagnosis of dementia. The optimal cut-off point for the two instruments was determined, and sensitivity, specificity, positive and negative likelihood ratios were calculated at different cut-off points.

The association between the scores on the two instruments, the education level and the scores on the scales of severity of cognitive impairment was investigated using Spearman's correlation coefficient.

In order to test differences between subject groups, non-parametric tests were used such as Chi-square Mann–Whitney test and Wilcoxon's rank sum tested for comparisons between two groups and the Jonckheere–Terpstra test when comparisons involved three or more groups (assuming to have a natural order).

Data were recorded and analyzed using the SPSS v.13.0 statistical package.

The demographic and clinical characteristics of the 97 subjects are summarized in Table 1. There was a preponderance of low education level, and 57.8% had not completed their primary education (less than 6 years of education). Thirty-five subjects (36.1%) were diagnosed with dementia and 10 individuals (10.3%) met criteria for mild cognitive impairment. No difference was found between demented and non-demented patients in education level (z=−0.8, p=0.42) or gender (χ2=0.12, p=0.73). Women had a lower level of education (z=−2.63, p=0.009).

There were no statistical differences in age, gender, education or main diagnosis between the 18 excluded subjects from the validation study and those included in the analysis (data available upon request).

The area under the ROC curve (AUC) for the RUDAS was 0.901 (CI 95% 0.84–0.96), hence similar to the MMSE AUC, which was 0.889 (CI 95% 0.82–0.95) (Fig. 1). The best cut-off point for the RUDAS was 21/22 with 94.3% sensitivity and 72.6% specificity. The best cut-off point for the MMSE was 16/17, thus much lower than the standard 23/24, with 85.7% sensitivity and 77.4% specificity. At the standard cut-off point the specificity of the MMSE was as low as 29% (Table 2).

Figure 1.

ROC curve for the RUDAS and MMSE in 97 subjects.

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Likelihood ratios (LR) at different cut-off points are also presented in Table 2. RUDAS scores less than 22 multiplied the pre-test odds of dementia by 3.4, while higher scores divided the pre-test odds by 5.5 (negative LR 0.18). MMSE scores less than 17 multiplied the pre-test odds of dementia by 3.8, while higher scores divided the pre-test odds by 12.5 (negative LR 0.08). At the published cut-off point for the MMSE (23/24), a positive test multiplied the pre-test odds for dementia by only 1.4, while for RUDAS considering cut-off point at 22/23, positive test multiplies pre-test odds by 2.2.

The RUDAS and MMSE scores correlated significantly (r=0.707, p<0.0001). RUDAS scores were higher than MMSE scores in subjects with a low level of education and the opposite was true in subjects with higher levels of education. Thus, the mean and standard deviation of the difference between RUDAS–MMSE scores in the different educational level groups were: illiterate 5.5±3.6; less than 6 years of education 3.4±4.3; 6–8 years 0.7±3.8; 9–12 years −0.33±2.8 and more than 12–1.0±0.0.

Both RUDAS and MMSE correlated with age, GDS and CDR (Table 3). The MMSE correlated with education level (r=0.402, p<0.0001), but the RUDAS did not (r=0.088, p=0.39).

No significant gender differences were found for the RUDAS (20.65 vs. 19.80, p=0.67) but a trend towards lower mean score in women was observed for the MMSE (19.65 vs. 16.95, p=0.06).

The Jonckheere–Terpstra test was used for comparisons between low educated females (n=49), low educated males (n=7), highly educated females (n=25) and highly educated males (n=16). Significant differences were found for the MMSE (J–T statistic=3.64, p<0.0001), but not for the RUDAS (J–T statistic=0.7, p=0.49). Fig. 2 shows these results as a box-plot graphic.

Figure 2.

Comparison between RUDAS and MMSE results according to gender and education.

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Effects of age, gender and education on the performance of the two screening tools were also evaluated using logistic regression (Table 4).

The rate of false positives was 27.4%, which equates to 17 subjects, of which 11 had borderline dementia (CDR=0.5) and 13 received a score equal to or higher than 2 in the GDS. Within the subgroup of 6 subjects who did not show any sign of dementia (CDR=0), four participants had low or zero scores at the memory item (data that was not consistent with clinical evaluation) and two scored low in praxias. The only subject within this 6-subject subgroup who did not suffer from any mental illness had a RUDAS score of 21.

In comparison with true negatives (subjects correctly classified as no dementia sufferers), false positives were significantly older than (mean age 78.9 vs. 75.6, p=0.022), but there were no statistical differences regarding gender or schooling. False positives scored lower than true negatives in the RUDAS (median 19 vs. 25, p<0.0001) and also in the MMSE (median 17 vs. 21, p=0.0009).

The clinical context and the model of work of our Psychogeriatric Unit, where the subjects for this study were recruited, which includes a comprehensive assessment, provides reliability for the clinical diagnosis of dementia (ICD criteria), the gold standard in this study. Patients received input from the multidisciplinary team (a psychiatrist, a psychologist and a social worker) who arranged the care plans and prolonged the follow-up periods for as long as needed. This procedure reduced the rate of false positives and false negatives, regarding a clinical diagnosis of dementia (which was the gold standard in this study), which is of particular concern in cases with no severe cognitive impairment at first contact (potential false negatives otherwise).

Also, fewer cases of advanced dementia (score on CDR=3) were included in comparison with the similar study of Storey et al. (8.6% vs. 31.8% of all dementias) and the prevalence of potential dementia (CDR=0.5) in the total sample was much higher in our study (23/97=23.7% vs. 6/111=5.4%). Furthermore, our sample had a prevalence of dementia cases of 36.1% (35/97), while the prevalence in the above study was 56.8% (63/111), and therefore, closer to 50%, a level of prevalence at which screening instruments work better.29 In other words, our study made the screening instruments subject to a more challenging test, which interestingly the RUDAS has successfully passed, yielding good to very good psychometric parameters. Indeed, we found a smaller difference in our sample between the median of the scores on the MMSE in demented (13, Q1: 9–Q3: 16) and in non-demented (20, 17–24) patients than in previous studies. This was also observed for the RUDAS (17, 10–19 vs. 23, 21–25).15,16

However, this clinical context may be also a constraint when generalizing our results. Thus, most of the non-demented subjects were psychiatric outpatients. On the one hand, this means that the sample was likely to be representative. On the other hand, our findings may not generalize to the general population, particularly to those patients with cognitive impairment or dementia who only receive primary care. Specifically, participants in this study may have been recruited due to risks or complexities which do not apply to all patients with dementia.

Nevertheless, the Spanish RUDAS confirmed the lack of biases associated with education level or gender, thus behaving as a more adequate test for the screening of dementia in our population. These promising results add new evidence to the usefulness of RUDAS for screening dementia when the risk of socio-cultural biases is high, particularly in people with low education level. Future research in primary care and in the community settings is needed in order to replicate these results and establish the most optimal cut-off point of the RUDAS. Meanwhile, based on our results we would recommend the use of RUDAS over the MMSE for the screening of dementia in people with low levels of education such as the Galician population.