Delirium in Old Age

August 2005 Update

Chapter 2: The instrumentation of delirium

Caution about “psychometrics” of scales at last emerging

Bhat and Rockwood have cautioned against the assumption that the inter- rater reliability of delirium rating scales can be assumed to be as good as that shown in original published studies of these scales (2005) They point out that delirium research is carried out in a wide range of settings, with a wide range of raters, and make the obvious point that reliability should be re-evaluated when the setting in which the scales used his different from that in which she was developed. However they do not go so far as to say that it should be re-evaluated every time it is used, and it appears that they are confident that inter- rater reliability is not also significantly affected by the raters themselves.

Instruments

The CAM itself has been validated in emergency rooms (Monette, Galbaud du, Fung et al (2001). It is now available in Portuguese (Fabbri, Moreira, Garrido et al (2001). Gonzalez and colleagues in Barcelona have translated the CAM into Spanish but could not resist changing it in order to "improve its psychometric properties" (2004). These included inter-rater reliability, concurrent validation and convergent validity,. Using small samples, they were able to convince themselves that they had achieved this objective. Their adaptation essentially replaced the CAM with a structured interview and could be regarded as a completely different approach to assessment from the original. The creation of only slightly different versions of the same measure, however, is to be deplored.

Inouye and colleagues (2005) have developed a version of the CAM that can be derived from clinical records. They found that it was less accurate than the clinical assessment, but sufficiently useful to be used in audit and quality improvement programmes when individual patient assessment was not feasible.

A Finnish study of the relationship between the CAM and ICD110/DSM categories has found a lower rate of agreement than previous studies- the best was with DSM-IV Laurila, V, Pitkala et al (2002)

Confusion Assessment Method for the Intensive Care Unit (CAM-ICU)

Ely, Margolin, Francis et al (2001) have validated a modification of the Confusion Assessment Method (CAM) for intensive care units (CAM-ICU). It as been directly compared with its parent by McNicoll, Pisani, Ely et al (2005). The CAM appeared to pick up some subtle cases of delirium there will not identified by the CAM-ICU. However this was particularly true for patients who were still able to talk. It is suggested that, although there was broad agreement between the two versions, the CAM-ICU might be better in patients unable to talk. Bergeron and colleagues have legitimately pointed out that disturbance of consciousness, a feature measured by most DSM-based delirium measures, is not likely to be a particularly helpful sign in intensive care unit delirium (2005). They therefore recommend the use of the CAM-ICU which does not rely upon this sign. Lin and colleagues (2004) reported on its use in 120 patients who were mechanically ventilated. Many were over the age of 65. Senior psychiatrists provided independent assessment of delirium, and they found a high level of criterion validity. There was a significant relationship between delirium and survival. 22.4% of their sample developed delirium, but these were not broken down by presence or absence of predisposing factors. The CAM-ICU score is associated with restraint use (Micek, Anand, Laible et al, (2005)

Intensive Care Delirium Screening Checklist

Roberts, Rickard, Rajbhandari et al (2005) used the Intensive Care Delirium Screening Checklist of Bergeron, Dubois, Dumont et al (2001) in a large Australian prevalence study of delirium in intensive care. This was originally developed in 93 intensive care patients, with a very high sensitivity but lower specificity against independent clinical assessment of delirium by psychiatrists. However they found a much lower incidence rate of 47% than the 83-87% found using the CAM-ICU in American work. They suggest a head-to-head comparison of these methods might be fruitful.

Delirium Rating Scale(DRS)

has been modified by Trzepacz, Mittal, Torres et al (2001) (see correction Anonymous (2001)), partly because of its inability to distinguish hypoactivity and hyperactivity. It appears to be better correlated with successful reporting of delirium in discharge summaries than its predecessor (van Zyl and Davidson (2003).
It is available in Italian and Japanese (Grassi, Caraceni, Beltrami et al (2001)

Comparison of DRS &CAM

In a head-to-head study our group has shown high levels of agreement between the two main delirium assessments used in research- the CAM and DRS (Adamis, Treloar, MacDonald et al (2005). However, they were both administered by the same highly-trained researcher and it remains to be seen whether the CAM performs as well as the DRS when in less experienced hands

Memorial Delirium Assessment Scale

Is available in Japanese (Matsuoka, Miyake, Arakaki et al (2001).

NEECHAM confusion scale

There has been further study of the predictive validity of the NEECHAM confusion scale (NCS) in patients with hip fracture by Johansson, Hamrin, & Larsson (2002). Matsushita, Matsushima, & Maruyama (2004)found it useful in improving recognition of delirium by medical staff. Milisen and colleagues have developed a Flemish version (2005).

Delirium Observation Screening Scale

A new nurse-observation scale for the detection of DSM-IV delirium -the Delirium Observation Screening Scale- has been developed by Schuurmans, Shortridge-Baggett, & Duursma (2003) . It appears to be preferred by nursing staff to the NEECHAM (van Gemert and Schuurmans (2004).

Cognitive Test for Delirium

has been validated against DSM-IV criteria in traumatic brain injury patients in a neurorehabilitation centre Kennedy, Nakase-Thompson, Nick et al (2003)

Delirium Elderly At-Risk DEAR

Freter, Dunbar, MacLeod et al (2005) have described a method of predicting post-operative delirium in elective orthopaedic patients . Using a simple checklist of risk factors (the DEAR: use of hearing aid or poor sight, ADL, MMSE, previous post-operative delirium, and substance misuse) they were able to predict the incidence of delirium in 132 patients undergoing elective orthopaedic surgery to hip or knee. Delirium occurred in 18 of these patients, with the best cut point on the DEAR scale having a sensitivity of 0.61 and a specificity of 0.76. This sounds promising, but may mean that as few as 30 percent of DEAR-positive patients became delirious in the development cohort. It is surprising that no test cohort was reported. Despite the authors optimism, this instrument cannot yet be recommended for everyday clinical use.

Strain of Care for Delirium Index

Milisen, Cremers, Foreman et al (2004) have developed a questionnaire to measure the "strain" of care for delirium, to be used by nursing staff. They freely acknowledge the usual absence of all the aspects of good nursing care necessary to prevent and minimise the consequences of delirium. They are in agreement with the notion that while reducing strain for nursing staff cannot be an end in itself, an intervention which improved outcomes for patients at the expense of increased strain for nurses would be far less valuable than one that had no effect or even reduced it (personal communication)

The Delirium Index

McCusker and colleagues have reported on further development of the Delirium Index (DI: (2004). This is a severity measure based on the Confusion Assessment Method (CAM). They combined the data from 2 concurrent studies. Patients over 65 admitted to acute care hospital were screened using the Short Portable Mental Status Questionnaire (Pfeiffer (1975). Those showing some impairment were then administered the CAM. A subsample of those with no impairment were also selected. Independent assessment using the DI was then carried out. Prior functional and health status data were collected. Inter- rater reliability assessment was carried out on a sample of 26 patients with 39 pairs of ratings. The internal reliability of the DI seems high; the intra-class correlation coefficient was98. The performance of the DI was assessed in patients with and without pre-existing cognitive impairment using the IQ code. Assessments were carried out every few days and then weekly during hospitalisation. Two different measures of fluctuation were derived from the DI and these correlated well with patients’ independent diagnosis of delirium. There was also some correlation between fluctuation in the DI and patients without delirium but with dementia. However they were obliged to remove one item of the DI (perceptual disturbances) after their test of internal reliability. They also found that the DI was positively associated with measures of physical illness in delirium but this did not apply in patients with delirium and dementia. They suggest that aetiological factors in patients with delirium and no preceding dementia might be different from those with dementia. They also reflect on the possibility that the relationship between delirium and mortality is less in patients with pre-existing dementia than without.

Nursing Delirium Screening Scale (Nu-DESC)

Gaudreau, Gagnon, Harel et al (2005b) have introduced a new rating scale: the Nursing Delirium Screening Scale (Nu-DESC). This has been derived from the Confusion Rating Scale (Williams, Ward, & Campbell (1988). They justify this because the confusion rating scale did not work very well with hypoactive patients - the majority of delirious patients, and the new scale include an item on psychomotor retardation. As with the parent instrument, they decided to maximise its sensitivity had the expense of specificity. The instrument takes just one minute to use, and is proposed as something that can be done regularly over long periods of time. During their study, 146 patients were admitted to the unit and screened using Nu-DESC. Fifty-two patients were assessed using the Confusion Assessment Method based on DSMIII-R. The Memorial Delirium Assessment Scale and DSMIV criteria were also applied. All the index assessments were applied independently of the Nu-DESC. Unfortunately, they do not described how they sampled those who ultimately received the validation assessments, and they also included data on seven patients who were assessed twice. The prevalence of CAM positive delirium was 35 percent of admissions to the combined oncology and internal medicine unit. The patient demographics are not described. The Nu-DESC performed very well against the CAM and achieved a positive predictive value of .77 and a negative predictive value of .91. However, the CAM itself is not a perfect predictor of delirium, and the relationship of the Nu-DESC to "gold standard" delirium remains unknown. Nevertheless this instrument does appear to have great promise by virtue of its brevity and accuracy. In the same study the authors compared the Nu-DESC and the CRS with the outcome being time to delirium recognition. Kaplan Meier curves showed a significant advantage of Nu-DESC over the CRS (Gaudreau, Gagnon, Harel et al (2005a).

MMSE

O'Keefe and colleagues have described how using the MMSE at admission and six days later is highly predictive of the diagnosis of incident delirium (2005). A fall of two or more points had a sensitivity of 93% and specificity of 90%t against new delirium on the second occasion, and a rise of three points or more had a sensitivity of 77% and a specificity of 75% against improvement of prevalent delirium by the second occasion. They recommend routine MMSEs in acute and medical care of older people.

Chapter 2 Reference List

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