Nu-DESC validation studies in multipurpose hospitalization units, where the incidence of delirium varies between 14.9-18.2 % and the mixed and hyperactive type prevails, demonstrate a moderate detection capacity with a sensitivity of 42-77.1 %> and specificity between 76-98 %> when the threshold is > 2, compared to short-CAM whose sensitivity is 8.6-11.1 %> and specificity is 100 %>. Also, it has optimal operational feasibility as it can be completed in approximately 2 minutes, which promotes the adherence of nursing professionals (approximately 90 %>) to its use in the healthcare practice²⁹.

This measurement tool also responds to the characteristics of this pathology, such as fluctuation or severity of symptoms per type of presentation. This result is consistent with DSM-V criteria, as Kim et al. point out³⁰, identifying significant variations of symptoms in 244 hospitalized psychiatric patients when Nu-DESC scores showed that severe symptoms increased during the afternoon or at night. Patients with hyperactive and mixed type of delirium had higher scores in the disorientation, inappropriate behavior, and inappropriate communication items than patients with unspecified or hypoactive delirium. The difference between these types is a higher average score in psychomotor retardation and more significant fluctuations during the afternoon, while at night, the symptoms of hyperactive type intensified. Patients who had the hypoactive type had the highest average score in the psychomotor retardation item that differs from the unspecified type, whose fluctuations occur mostly during the day³⁰.

Concerning low diagnostic sensitivity, associated with the limited capacity to detect hypoactive delirium, a study was conducted in three hospitalization units with a sample of 405 patients (103 participants were admitted to neurology, 84 to general medicine, 82 to general surgery or orthopedics, and 136 to neurosurgery), 185 of which had delirium (11 % hypoactive type). It showed no statistical differences between the groups regarding age, sex, hospitalization unit, language, and post-operative state. This result indicates increased sensitivity ranging from 42 %> to 67 %> when the threshold is > 1; however, specificity decreased from 98 % to 93 %³¹.

Another exploratory analysis was conducted within a study of 315 patients admitted to an emergency unit for at least 12 hours, where the incidence of delirium was 14.9 %, with a predominance of the hypoactive type (46.8 %). It showed that the evaluation of item 1 (disorientation) combined with two elements of the Mini-Mental State Examination (MMSE) indicates that asking the patient the day of the week and name of the unit where he or she is located increases sensitivity from 66 %> to 77.8 %>. This finding contrasts with the results obtained in the same study, where the disorientation item was not identified in 14 of 16 false positives cases³². Although questions arise about the ability of Nu-DESC to detect all forms of delirium, it is necessary to add the capacity to discriminate between delirium and differential diagnosis; Spendale et al. demonstrated it in a study of 101 patients hospitalized in different units where 79 %> of positive cases had a history of cognitive impairment³³.

Studies conducted in post-operative patients admitted to the ICU, where hypoactive type delirium predominates, show that Nu-DESC is a practical tool for delirium detection and has a sensitivity of 65.5-100 % and specificity of 81.3-86 %. When considering the type of surgical intervention, a trend towards overestimating the incidence of Post-operative Delirium (POD) in patients undergoing non-cardiac or intracranial interventions was identified because of the number of false positives (n = 9) and positive predictive value (57 %>). Abelha et al.³⁴ reported this in a study of 78 patients admitted to the ICU, where Nu-DESC performance was compared with the ICDSC as a gold standard.

When applying the Nu-DESC on days 1 to 4 of the post-operative period in patients undergoing scheduled cardiac surgery, the detection capacity decreases considerably from 65.6 %> (day 1) to 46.9 %o (day 4) when the threshold is > 2. These results are associated with underestimation of hypoactive delirium that, due to its signs, unlike the hyperactive type, does not demand attention. However, it requires more monitoring for identification, accounting for the difference in diagnostic sensitivity between days 1 and 4 because on day one, the scale was applied in the ICU where the nurse-patient relationship was closer than in the general room, where it was applied on day 4.

Although changing care units implies diminution in suggestive sign detection (because of the fluctuating characteristics of delirium and the nurse/patient ratio), a change in the cognitive performance of patients is observed as the number of cases of delirium decreases on day 4 (n= 49), mostly with the hypoactive type (n = 28); the Nu-DESC detected just 50 % (n =14) of those cases. Therefore, the evidence does not support that Nu-DESC detects the symptoms of hypoactive delirium optimally since there is a tendency to recognize the hyperactive type³⁵ mostly.

In adding all the articles reviewed in this area, approximately 1,500 patients were assessed for POD at different times: before surgery (where the Nu-DESC and MMSE were used to assess the pre-operative cognitive function³⁶), ten minutes after extubation to verify ongoing delirium³⁷, upon admission to the PACU, upon discharge from the unit^{(36, 38)}, or up to 14 days after surgery³⁹. Previously, it was necessary to train the nursing staff in topics like delirium and application of the Nu-DESC³⁶. During the assessments, it was demonstrated that the execution time of the Nu-DESC does not take more than two minutes⁴⁰.

When making a detailed comparison with the CAM-ICU, it was found that its discriminatory characteristics are not better than this standard diagnostic criterion; therefore, it should not be replaced, despite low staff adherence due to difficulties in its application. However, the Nu-DESC showed a moderate agreement, according to the kappa coefficient (0.514)⁴¹. At the same time, the results obtained by the Nu-DESC were compared or complemented with other scales such as the Richmond Agitation and Sedation Scale (RASS), the Post-Anesthetic Recovery Score (PARS), the Neelon and Champagne Confusion Scale (NEECHAM), the Canadian Neurological Scale (CNS), the Bispectral Index (BIS), the Glasgow Coma Scale, (GCS) and the Ramsey Scale, showing high reliability in the Nu-DESC to detect POD^42-44.

POD was evaluated by the Nu-DESC in patients between 16⁴⁵ and over 80 years old, finding that the most affected patients were older adults (> 65), especially those over 80³⁹ who had ASA 3 or 4 in the pre-surgical period, while younger patients (with ASA 1 or 2) developed delirium in a smaller amount. Age influenced the incidence of delirium, which was between 4.3 % (45) and 12.3 %>³⁹ in post-operative patients, who also had a more extended stay in the PACU (24 % vs. 10 %) and hospitalization unit (7 vs. 4 days) compared to those who did not develop POD⁴⁶. Studies also showed that the Nu-DESC is highly effective in detecting hyperactive and mixed types, and moderately effective in the hypoactive type⁴⁷, with higher scores for disorientation and psychomotor retardation⁴³.

Regarding discriminatory capacities, a sensitivity between 69 - 96 % and specificity between 82-100 % were reported (40). Neufeld et al.⁴⁰ and Saller et al.³⁸ found that the > 1 threshold is more sensitive for the Nu-DESC (69 % (vs. 32 %) and 54.5 % (vs. 27 %), respectively). However, significant changes that affect specificity by decreasing it from 92 %> to 80 %> are also described⁴⁰.

One of the recommendations given by Smulter et al.⁴⁷ is to have better reports in clinical records about clinical findings in the PACU because, of all the patients who develop delirium in this unit, only 23 % are diagnosed and 1 % correctly identified and registered. The Nu-DESC also showed improvement in the recognition rate and allowed clinical staff to better record the findings⁴⁶.

Despite the incidence and prevalence of delirium, particularly the hypoactive type, it is poorly recognized in patients who require palliative care or specialized care due to malignant tumor diagnosis. Clinical condition factors and patient's comorbidities, such as fatigue or depression, may make it challenging to recognize cognitive changes associated with delirium⁴⁸.

While multiple detection methods have been developed and validated, such as the Cognitive Rating Scale (CRS), Memorial Delirium Assessment Scale (MDAS), Confusion Assessment Method (CAM), and Delirium Rating Scale-Revised-98 (DRS-R-98), these instruments are very complex to be applied or do not have adequate discriminatory power compared with the Nu-DESC. Although recent studies reported a lower discriminatory power when the threshold is > 2 (63 %)⁴⁸, the original study indicates that the Nu-DESC has greater sensitivity (85.7 %>) when the threshold is > 1. This result corroborates what was mentioned in the categories above and should be considered in subsequent studies³.

Regarding the ability to detect hypoactive delirium (which is also related to our findings and the most underdiagnosed type), questions are raised about measuring the psychomotor delay, which can be linked or not as a symptom of delirium detected by health care personnel or caregivers. Many patients receive pharmacological treatment for symptom management, casting doubts about its application time, changing the outcome of the Nu-DESC⁴⁹, and increasing the number of false positives or false negatives as reported by Gaudreau et al.³ (who associated severe analgesia as a factor that makes it difficult to establish a correct diagnosis). Besides, the findings of Hosie et al.⁵⁰ indicate an overestimation of the incidence of delirium by the Nu-DESC since only 19 % of the evaluations were carried out on patients in the "stable" or "deteriorating" palliative care phases and terminal phase, following the DSM-V criteria.

Articles in languages different from Spanish, English, or Portuguese were not included, neither the category of delirium in oncology patients.

The literature reports the importance of early and routine detection of delirium in clinical practice. So, nurses need to know easy-to-use tools like the Nu-DESC scale, which is applicable in different hospital areas, to create a culture of prevention, detection, and management of delirium.