Psychosomatics 45:426-431, October 2004
© 2004 The Academy of Psychosomatic Medicine
Instrument for Detection of Delirium in General Hospitals: Adaptation of the Confusion Assessment Method
M. González, M.D., Ph.D.,
J. de Pablo, M.D., Ph.D.,
E. Fuente, M.D.,
M. Valdés, M.D., Ph.D.,
J.M. Peri, Ph.D.,
M. Nomdedeu, M.D., and
S. Matrai, M.S.
Received June 16, 2003; revision received Dec. 19, 2003; accepted Jan. 30, 2004. From the IDIBAPS Clinical Institute of Psychiatry and Psychology and the Internal Medicine Department, Hospital Clínic, University of Barcelona, Spain. Address reprint requests to Dr. de Pablo, Sección de Psiquiatría de Enlace del Instituto Clínico de Psiquiatría y Psicología, Hospital Clínico de Barcelona, Villarroel 170, 08036 Barcelona, Spain; jdepablo{at}clinic.ub.es (e-mail).
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ABSTRACT
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Delirium is a common and severe disorder that is often misdiagnosed. The use of screening instruments is advisable for its early detection and treatment. In this study, the authors present an adaptation of the Confusion Assessment Method in order to improve its psychometric properties. One hundred fifty-three elderly inpatients were assessed in a four-phase procedure. Interrater reliability was high (kappa=0.89). Sensitivity was 90%, and specificity was 100%; the value for negative predictive accuracy was 97%, and the value for positive predictive accuracy was 100%. The adaptation has convergent agreement with two other mental status tests, the Mini-Mental Status Examination and the Delirium Rating Scale. Our results suggest that the adaptation of the Confusion Assessment Method is sensitive, specific, reliable, and easy to use by clinicians.
Key Words: hospital treatment • delirium
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INTRODUCTION
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Delirium has been described since the beginning of the medical literature as an acute clinical disorder of attention and cognitive functioning. The prevalence of delirium in hospitalized patients increases with age.1 The rates range from 15% to 50%, depending on the diagnosis at admission.2 It is one of the most common psychiatric syndromes in the hospital setting,3 with an associated mortality rate varying from 10% to 65%.4 In a European multinational investigation with 3,608 patients at six Spanish hospitals, a prevalence rate of 9.1% was obtained.5 The hospital stay for patients with delirium is significantly longer than for those with other psychiatric diagnoses: an average of 17.5 days versus 12 days,6 with higher hospital costs and increased rates of palliative care after discharge. A study carried out in the United States estimated that hospital and nursing costs could reach $17.5 million per day for the whole country.7 Despite its clinical and economic importance, according to available data, delirium is a medical emergency that is not properly recognized in 32% to 67% of cases, and its treatment is usually delayed.8
New diagnostic criteria have been developed to increase reliability and validity in diagnosing delirium,9,10 focusing on the differential diagnosis between delirium and other psychiatric syndromes, such as dementia, depression, and psychosis.
Most of the currently used indices for the detection of delirium were designed specifically for the detection of cognitive impairment, so they are not specific for identifying delirium. Specific indices for the detection of delirium are often too complex for nonpsychiatric clinicians to use, and they take too long to be completed.
A new index, the Confusion Assessment Method, proved to be specific and sensitive for the detection of delirium,11 and it has been validated.12–14 The main objective of the authors was to develop a method of enabling nonpsychiatric clinicians to easily and quickly diagnose delirium in different care settings. The Confusion Assessment Method is based on the operational application of the DSM-III-R diagnostic criteria. It takes about 5 minutes to complete and provides a diagnostic algorithm for delirium based on the presence of the two cardinal features (acute onset, fluctuating course, and inattention) and at least one of the two secondary features (disorganized thinking and altered level of consciousness). Sensitivity values were 100% and 94%, specificity values were 95% and 90%, positive predictive accuracy values were 91% and 94%, and negative predictive accuracy values were 100% and 90%. The Confusion Assessment Method was shown to have high convergent agreement with the Mini-Mental State Examination (MMSE),15 an index for the detection of cognitive alterations.
The aim of the present study was to adapt and validate the Confusion Assessment Method to improve its psychometric properties and provide clinicians with a screening instrument for a more accurate diagnosis of delirium.
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METHOD
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The adaptation and validation of the Confusion Assessment Method were developed in four phases.
Phase 1: Translation and Adaptation
An expert panel that included four psychiatrists, an internal medicine physician, and a clinical psychologist at the Hospital Clínic of Barcelona translated and adapted the Confusion Assessment Method following the original criteria. The adaptation, like the original version, consists of the application of an algorithm based on the essential diagnostic criteria from DSM-IV. The expert panel tested the successively improved versions of the instrument by its blind administration to three series of six patients with and without delirium to estimate its effectiveness and to introduce the necessary changes. Each panel member independently completed a list of remarks on the instrument. In addition, a group that included six physicians of different specialties was given the instrument with short instructions. They administered it to three patients and filled in an evaluation form on the instrument and its administration. With all of these data, the expert panel designed the final version.
Phase 2: Interrater Reliability
The interrater reliability16 was determined by a study with 30 patients over 65 years of age (15 with and 15 without delirium). A psychiatrist expert in the detection of delirium at the consultation-liaison psychiatry ward at the Hospital Clínic of Barcelona selected inpatients over 65 years of age from any of the hospital's wards, excluding psychiatry. From these patients, those with severe aphasia, mechanical ventilation, and linguistic barriers and those who refused to participate or whose participation was refused by the family or the legally responsible person were excluded. The psychiatrist acted as a "gold standard" and determined through clinical interview whether the selected patients presented delirium in accordance with DSM-IV criteria and also by using the patient's medical record and two specific instruments, the validated Spanish versions of the MMSE17 and the Delirium Rating Scale (DRS),18 an index designed to evaluate the severity of delirium symptoms.19 Each patient with delirium was paired with another patient without delirium of the same age. The selected patients were assessed simultaneously and independently by two raters: a general physician and a psychiatrist who administered the Confusion Assessment Method adaptation. They had no previous contact with the patients and had no information on their medical record.
Phase 3: Concurrent Validation: Sensitivity and Specificity
Concurrent validity was determined by establishing the instrument's sensitivity and specificity to detecting delirium against the psychiatrist's evaluation.
Study Group
We established that the study group for this phase had to include 30 patients diagnosed with delirium in order to obtain sufficient power to determine sensitivity and specificity. In a 6-month period, one bed was selected at random every day from all the beds of inpatients of over 65 years of age with a length of stay of over 24 hours, excluding the psychiatry ward. One hundred twenty-three patients were evaluated to obtain the study group of 30 patients with delirium. The 123 patients were divided into two groups, according to the presence or absence of dementia. The diagnosis of dementia was established on the basis of DMS-IV criteria, medical records, MMSE rating, and interviews of relatives.
Procedure
First, either the general physician or the psychiatrist who had shown high interrater reliability in phase 2 evaluated the randomly selected patient with the Confusion Assessment Method adaptation. They were blinded to the patients' medical record and had no previous contact with them. In approximately the next 30 minutes, the "gold standard," blind to the results obtained with the Confusion Assessment Method adaptation, evaluated the presence of delirium in the patient, as in phase 2. We established a short time between the two evaluations to avoid any possible bias due to the fluctuating nature of delirium.
Phase 4: Convergent Validity
Convergent validity was evaluated by assessing the relation between the Confusion Assessment Method adaptation and the MMSE and Delirium Rating Scale scores in the study group of phase 3. On one hand, the four items of the Confusion Assessment Method adaptation evaluating cognitive impairment (see Appendix 1, items B1–B4) were scored to obtain a global rating at the cognitive assessment, with scores ranging from 0 to 4. We calculated the correlation between this global rating obtained by the blinded rater with the Confusion Assessment Method adaptation and the MMSE rating obtained with the "gold standard."
On the other hand, the items in the second part of the Confusion Assessment Method adaptation (see Appendix 1, items 1–4) were also scored, and the final rating (from 0 to 4) was used to calculate the correlation with the Delirium Rating Scale score obtained by the "gold standard." Scoring for the Confusion Assessment Method was solely used for the purpose of calculating the correlations between the instruments.
Statistical Analysis
All information was collected in standardized formats, codified, and introduced twice in the database. The SPSS program for Windows (version 10.0) was used. To establish the interrater reliability, the kappa coefficient ( ) was calculated as the index of concordance exceeding chance for interrater reliability and convergent validity.
The sensitivity and specificity were calculated with standard Bayes theorem formulae. The likelihood ratio for a positive test was defined as follows: sensitivity/(1–specificity).20 To assess convergent validity, Pearson's correlation coefficients were calculated in the case of normal distributions and Spearman's coefficients for distributions that were not normal.
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RESULTS
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Phase 1: Translation and Adaptation
The expert panel detected that nonpsychiatrists do not use the proper clinical criteria for assessment and therefore elaborated a two-part structured interview in order to optimize the collection of clinical data. The first part aims to obtain information on the disorder's onset and course and consists of two open questions to the person caring for the patient. The second part aims to determine the presence of cognitive alterations in the patient and consists of two open questions to evaluate thinking and attention and three items extracted from the Spanish version of the MMSE16 to evaluate consciousness (orientation in space and time) and attention. With the collected information, the clinician answers the following questions and applies the algorithm:
- Does the patient have an acute and fluctuating mental disorder?
- Does the patient have difficulty focusing attention?
- Is the patient's thinking disorganized?
- Is the patient's level of consciousness altered?
In agreement with the original algorithm, the diagnosis requires a positive answer to the first two questions and to the third and/or fourth one.
The expert panel reached agreement on the adaptation's final version (Appendix 1). They agreed that every item of the interview includes relevant symptoms for the application of the algorithm. They also concluded that the adaptation, on the whole, had high face validity.
The algorithm was easily understandable because the raters were able to complete all items for all patients and proved easy to use by clinicians after a short training. The average time for completion was 6.99 min (SD=1.45). In contrast, the evaluation made by the "gold standard" psychiatrist could require as long as 60 minutes.
Phase 2: Interrater Reliability
In this phase, a group of 30 patients (15 with and 15 without delirium; mean age=77.73 years [SD=8.21]). Both the overall interrater reliability (kappa=0.89) and the concordance for each item separately were high. Our results and the values obtained for the original Confusion Assessment Method are shown in Table 1.
Phase 3: Concurrent Validation: Sensitivity and Specificity
In this phase, 123 patients were evaluated to obtain the final group of 30 patients with delirium. The characteristics of the study group are shown in Table 2. The occurrence rate of delirium in the study group was 24%. The Confusion Assessment Method adaptation's sensitivity was 90%, and its specificity was 100%. The positive predictive value was 1.00, and the negative predictive value was 0.97 (Table 3). Every item of the algorithm was evaluated in order to determine sensitivity and specificity separately. The final diagnostic algorithm proved to be the most effective for the detection of delirium (Table 3). Values for sensitivity and specificity were 87% and 100%, respectively, in the dementia group (N=62) versus 93% and 100%, respectively, in the nondementia group (N=61). Characteristics of both groups are shown in Table 4.
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TABLE 2. Characteristics of Patients Included in the Concurrent Validation Study (sensitivity and specificity) of the Confusion Assessment Method
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Phase 4: Convergent Validity
The Pearson's correlation between the Confusion Assessment Method adaptation cognitive items (B1–B4) and the MMSE was r=–0.84 (p<0.01). The Spearman's correlation between the items of the second part of the Confusion Assessment Method adaptation (1–4) and the Delirium Rating Scale was rs=0.78 (p<0.01).
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DISCUSSION
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During the adaptation process of the Confusion Assessment Method, the expert panel realized that nonpsychiatrists do not use the proper clinical criteria for cognitive assessment, which could facilitate false negative cases to appear in their diagnosis made with the Confusion Assessment Method in comparison with those made by psychiatrists. Therefore, our adaptation of the Confusion Assessment Method includes a structured interview procedure to identify delirium. The high values obtained for interrater reliability (kappa=0.89), sensitivity (90%), specificity (100%), and negative predictive accuracy (97%) suggest that our adaptation provides both psychiatrists and nonpsychiatrists with an accurate instrument for identifying delirium.
In our experience, a short training was sufficient for the clinicians to learn the basic clinical criteria in collecting data, and as in the original instrument, the detection of symptoms required a few minutes.
According to our results, the adaptation of the Confusion Assessment Method may be useful for the assessment of delirium in patients at high risk, such as elderly hospitalized patients with a high degree of cognitive impairment. It is important to underline that despite the high number of patients diagnosed with cognitive impairment in the total number of patients evaluated in the concurrent validation phase (50.4%), the Confusion Assessment Method adaptation was able to differentiate between dementia and delirium.
In our study, three false negative ratings were registered with the Confusion Assessment Method adaptation. In the first case, the "gold standard" was able to diagnose delirium because of the presence of sensoperceptive alterations with subacute onset and the worsening of the condition during the night. In the other two cases, the diagnosis of dementia was concurrent with other symptoms suggesting delirium with subacute onset and predominating apathy and psychomotor inhibition. Therefore, our instrument seems to have difficulty detecting delirium in those cases with subacute onset, as well as in patients with no cognitive alterations at the moment of the interview.
The fact that no false positive ratings were obtained in our groups suggests that the positive diagnosis for delirium with the Confusion Assessment Method adaptation is very likely to agree with the positive diagnosis made by the "gold standard."
The fact that the correlation between the Confusion Assessment Method adaptation and the MMSE, an index validated for the assessment of cognitive alterations, was found to be adequate suggests that our adaptation provides a proper cognitive assessment for identifying delirium. Furthermore, the correlation between the Confusion Assessment Method adaptation and the Delirium Rating Scale was also satisfactory.
The limitations of this adaptation and validation study of the Confusion Assessment Method are the age of the group (from which young patients were excluded) and the lack of assessment of other psychiatric disorders, such as schizophrenia or other psychotic conditions, because of the low prevalence in the selected population. By contrast, the high prevalence of depression and dementia in this older population allowed the assessment of the instrument in these two disorders.
In conclusion, the instrument developed in our study provides a more structured procedure of data collection and allows clinicians to properly detect delirium. However, future studies are required to reproduce our results in other study groups.
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ACKNOWLEDGMENTS
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Supported by a grant from the Ministry of Foreign Affairs of Spain to Dr. González.
The authors thank P. Santos, the Consultation-Liaison Psychiatry Department, and the Internal Medicine Department of the Hospital Clínic of Barcelona.
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REFERENCES
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- Folstein MF, Bassett SS, Romanoski AJ, Nestadt G: The epidemiology of delirium in the community: the eastern Baltimore mental survey. Int Psychogeriatr 1991; 3:169–176[CrossRef][Medline]
- Wise MG, Trzepacz PT: Delirium (confusional states), in Textbook of Consultation-Liaison Psychiatry, 1st ed. Edited by Rundell JR, Wise MG. Washington, DC, American Psychiatric Press, 1996, 259–274
- Lipowski ZJ: Delirium in the elderly patient. N Engl J Med 1989; 320:578–582[Medline]
- Inouye SK: The dilemma of delirium: clinical and research controversies regarding diagnosis and evaluation of delirium in hospitalized elderly medical patients. Am J Med 1994; 97:278–288[CrossRef][Medline]
- Valdés M, De Pablo J, Campos R Farre JM, Giron M, Lozano M, Aibar C, Garcia-Camba E, Martinez Calvo A, Carreras S, Stein B, Huyse F, Herzog T, Lobo A: [Multinational European project and multicentre Spanish study of quality improvement of assistance on consultation-liaison psychiatry in general hospital: clinical profile in Spain.] Med Clin (Barc) 2000; 115:690–694 [Spanish][Medline]
- Navinés R, Gómez E, Franco Jg, De Pablo J: Delirium in a consultation liaison psychiatry unit of a general hospital. Actas Esp de Psiquiatr 2001; 29:159–169
- Rizzo JA, Bogardous ST Jr, Leo-Summers L, Williams CS, Acampora D, Inouye SK: Multicomponent targeted intervention to prevent delirium in hospitalized older patients: what is the economic value?. Med Care 2001; 39:740–752[CrossRef][Medline]
- Inouye SK: Delirium in hospitalized older patients: recognition and risk factors. J Geriatr Psychiatry Neurol 1998; 11:118–125
- American Psychiatric Association: Diagnostic and Statistical Manual of Mental Disorders (DSM-IV), 4th ed. Washington, DC, APA, 1994
- World Health Organization: The ICD-10 Classification of Mental and Behavioural Disorders: Diagnostic Criteria for Research. Geneva, WHO, 1993
- Inouye SK, Van Dyck CH, Alessi CA, Balkin S, Siegal AP, Horwitz RL: Clarifying confusion: the Confusion Assessment Method: a new method for detection of delirium. Ann Intern Med 1990; 113:941–948
- Ely EW, Inouye SK, Bernard GR, Gordon S, Francis J, May L, Truman B, Speroff T, Gautam S, Margolin R, Hart RP, Dittus R: Delirium in mechanically ventilated patients: validity and reliability of the Confusion Assessment Method for the Intensive Care Unit (CAM-ICU). JAMA 2001; 286:2703–2710[Abstract/Free Full Text]
- Monett J, Galbaud du Fort G, Fung SH, Massoud F, Moride Y, Arsenault L, Afilalo M: Evaluation of the Confusion Assessment Method (CAM) as screening tool for delirium in the emergency room. Gen Hosp Psychiatry 2001; 23:20–25[CrossRef][Medline]
- Fabbri RM, Moreira MA, Garrido R, Almeida OP: Validity and reliability of the Portuguese version of the Confusion Assessment Method (CAM) for the detection of delirium in the elderly. Arquivos de Neuro-Psiquiatria 2001; 59(2-A):175–179
- Folstein MF, Folstein SE, McHugh PR: "Mini-Mental State": a practical method for grading the cognitive state of patients for the clinician. J Psychiatr Res 1975; 12:189–198[CrossRef][Medline]
- Gordis L: Epidemiology, 2nd ed. Philadelphia, WB Saunders Company, 2000, 75–81
- Lobo A, Saz P, Marcos G, Dia JL, de la Camara C, Ventura T, Morales Asin F, Fernando Pascual L, Montanes JA, Aznar S: [Revalidation and standardization of the mini-exam (first Spanish version of the Mini-Mental Status Examination) in the general geriatric population.] Med Clin (Barc) 1999; 112:767–774 [Spanish][Medline]
- Bulbena A, Corrons C, Amorós G, Martín-Santos R, Anguiano B: Escalas de delirium y orientación: adaptación castellana del Delirium Rating Scale y de la Orientation Scale. Rev Gerontol 1996; 6:245–254
- Trzepacz PT, Baker RW, Greenhouse J: A symptom rating scale for delirium. Psychiatry Res 1988; 23:89–97[CrossRef][Medline]
- Petrie A, Sabin C: Medical Statistics at a Glance. London, Blackwell Science Ltd, 2000, 90–92
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ABSTRACT
INTRODUCTION
