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Clinical Utility and Use of DSM–IV and ICD–10 Criteria and The Memorial Delirium Assessment Scale in Establishing a Diagnosis of Delirium After Cardiac Surgery

Received January 28, 2007; revised February 6, 2007; accepted February 8, 2007. From the Dept. of Old-Age Psychiatry and Psychotic Disorders, Medical University of Lodz, Poland; the Dept. of Cardiac Surgery, University Hospital No. 3, Lodz, Medical University of Lodz, Poland; the Dept. of Cardiology, University Hospital No 3, Lodz, Medical University of Lodz, Poland; the Dept. of Anesthesiology and Intensive Care, 2nd Chair of Pediatrics, Medical University of Lodz, Poland; and the Dept. of Anesthesiology and Intensive Cardiologic Care, University Hospital No 3, Lodz, Medical University of Lodz, Poland. Send correspondence and reprint requests to Jakub Kazmierski, M.D., Department of Old-Age Psychiatry and Psychotic Disorders, Medical University of Lodz, Czechoslowacka 8/10; 92-216 Lodz, Poland. e-mail: kubakaz3{at}wp.pl
© 2008 The Academy of Psychosomatic Medicine

ABSTRACT

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Authors evaluated the sensitivity and specificity of DSM–IV and ICD–10 criteria and the cutoff value of the Memorial Delirium Assessment Scale (MDAS) in diagnosing postoperative delirium in 260 cardiac surgery patients. Incidence of delirium diagnosed on the basis of DSM–IV and ICD–10 criteria, and with the use of the MDAS was 11.5%, 9.2%, and 6.5%, respectively. The DSM–IV criteria for delirium were found to be more inclusive than those of ICD–10. The cutoff point of 10 of the MDAS was optimal in relation to the presence or absence of delirium after cardiac surgery.

INTRODUCTION

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Delirium after cardiac surgery has been extensively described since the 1950s, when the first open-heart surgery was performed.¹ The reported range of incidence of delirium after cardiac surgery is wide (3% to 47%).² The recent results are more consistent, varying from 8% to 14%.^3,4 The reasons for such incompatible outcomes are the retrospective character of numerous studies, different methods and study design, year of publication of the study (the later the publication, the lower the incidence) and, finally, different diagnostic criteria and scales used in the studies. Ordinarily, researchers diagnose postoperative delirium on the basis of DSM–IV, DSM–III-R, and, especially in Europe, ICD–10 criteria, as well as diagnostic scales like the Confusion Assessment Method (CAM) and the Delirium Rating Scale (DRS). Diagnostic accuracy of DSM–IV, DSM–III-R, and ICD–10 criteria for delirium was previously evaluated in a population of elderly, hospitalized patients.⁵ However, the sensitivity, specificity, and "interscale" agreement of different diagnostic systems in estimating the incidence of delirium after cardiac surgery has not been investigated to date. Another important diagnostic instrument used in delirium studies, with the exception of studies on delirium after cardiac surgery, is the Memorial Delirium Assessment Scale (MDAS).⁶ To our knowledge, the accuracy of the MDAS in evaluating the incidence of delirium among patients after cardiac surgery has not been previously assessed.

Method

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After approval had been obtained from the Ethics Committee of the Medical University of Lodz, 296 patients consecutively admitted to the Department of Cardiac Surgery in Lodz for an open-heart procedure between November 2004 and March 2005 were asked to join the study; 260 patients signed an informed, written consent and were enrolled. Preoperative delirium was not observed. After the surgical intervention, DSM–IV and ICD–10 criteria were used to diagnose delirium.^7,8 All the patients were also evaluated with the use of the MDAS (cutoff score: 13).⁶ The assessment was made once, postoperatively, within 2 to 6 days by one of the two psychiatrists (JK, MK). Also, the patients were interviewed in case of any unusual behavioral change reported by the attending staff.

Statistical Analysis
A receiver operating characteristic (ROC) curve was plotted to show the sensitivity and specificity for various scores on the MDAS in comparison with DSM–IV and ICD–10 criteria of delirium. The sensitivity and specificity of DSM–IV and ICD–10 criteria were calculated by use of a programmed formula on an Excel spreadsheet. In order to establish the agreement in classification of patients according to the ICD–10 or DSM–IV criteria, we performed an "interscale" analysis. The Statistica 6.0 (Statsoft; Tulsa, OK, U.S.) and Medcalc (Medcalc; Mariakerke, Belgium) statistical software were used for all calculations.

Results

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Of the 260 patients, 198 (76%) were men. Their mean age was 62 years (standard deviation [SD]: 9.0; range: 25–81). For all participants, the incidence of delirium diagnosed in accordance with DSM–IV, ICD–10 criteria, and the MDAS was 11.5% (95% confidence interval [CI]: 7.6%–15.5%), 9.2% (95% CI: 5.7%–12.8%), and 6.5% (95% CI: 3.5%–9.5%), respectively. The sensitivity and specificity of DSM–IV criteria in estimating the incidence of delirium were 100% (95% CI: 86%–100%) and 98% (95% CI: 95%–99%), respectively. The sensitivity and specificity of the ICD–10 criteria were 80% (95% CI: 63%–91%) and 100% (95% CI: 98%–100%), respectively. The "interscale" agreement ( statistic) was 0.86 (95% CI: 0.77–0.94), with a standard error (SE) of 0.05, which is regarded as a very good agreement between the two. The exact number of patients classified according to both classification systems is shown in Table 1. The specificity and sensitivity for various values of the MDAS in comparison with the ICD–10 and DSM–IV delirium criteria are presented in Figure 1 and Figure 2. Areas under the curves (AUC) were 0.98 (SE: 0.02) for ICD–10 and 0.99 (SE: 0.02) for DSM–IV. In both cases, the cutoff values were established at a level of 10 points on the MDAS.

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TABLE 1. Classification as Delirium (D) or Non-Delirium (ND) Patients According to DSM–IV and ICD–10 Criteria

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FIGURE 1.  ROC Analysis for the MDAS and ICD–10 Criteria for Delirium ROC: receiver operating characteristics; MDAS: Memorial Delirium Assessment Scale; ICD–10: International Classification of Diseases, 10th Edition. The cutoff value was established at >9 points, with sensitivity of 95.8% and specificity of 93.2%. Cutoff values were established at a level of 10 points on the MDAS.

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FIGURE 2.  ROC Analysis for the MDAS and DSM–IV-Based Criteria for Delirium ROC: receiver operating characteristics; MDAS: Memorial Delirium Assessment Scale; DSM–IV: Diagnostic and Statistical Manual of Mental Disorders, 4th Edition. The cutoff value was established at >9 points, with sensitivity of 96.7% and specificity of 95.7%. Cutoff values were established at a level of 10 points on the MDAS.

Discussion

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The results of the current study indicate that there are differences in the incidence of postoperative delirium depending on the measures used by the researcher. Although the "interscale" correlation of 0.86 suggested good agreement between DSM–IV and ICD–10 diagnostic systems, we found that DSM–IV criteria for delirium were more sensitive but less specific than those of ICD–10. Moreover, the MDAS diagnostic score of 10 was established to be optimal in diagnosing delirium among cardiac surgery patients. Two of the patients who did not meet ICD–10 criteria for delirium were not disoriented, and recent memory impairment was not observed. Also, reduced level of consciousness and reduced ability to maintain and shift attention were only slightly expressed. Nonetheless, severe and moderate hallucinations, delusions, disturbed psychomotor activity, and disturbances in the sleep–wake cycle were found; thus, those participants fulfilled DSM–IV criteria and achieved the cutoff score of 13 points in the MDAS.

One of the patients without ICD–10-diagnosed delirium did not reveal recent memory impairment; however, other symptoms of delirium were present. Three other patients who did not meet ICD–10 criteria for delirium did not experience psychomotor or sleep–wake cycle disturbances. The differences between the prevalence of delirium diagnosis based on DSM–IV and ICD–10 diagnostic systems were probably the consequence of the more inclusive character of DSM–IV criteria, a feature that was previously observed by Cole et al.⁵ It is worthwhile to notice, however, that, in this series the differences in the incidence were not only due to patients without psychomotor or sleep–wake cycle disturbances who were diagnosed with delirium according to DSM–IV criteria. There was also another group of patients with only partly expressed change in cognition who were diagnosed with delirium according to DSM–IV, but not ICD–10, criteria. In our study, the MDAS diagnostic cutoff score of 10 produced optimal results in relation to the presence or absence of delirium. Breitbart et al.⁶ reported an optimal diagnostic cutoff value to be 13, whereas Lawlor el al.⁹ suggested an optimum MDAS diagnostic score of 7 in a population of AIDS and cancer patients. However, in the recent MDAS validation study in a psychogeriatric population, the cutoff score of 10 was established to be optimal.¹⁰ In our research, the individuals with delirium symptoms noticed during a psychiatric interview whose score in the MDAS was slightly below 13 had a full-blown, although usually less severely symptomatic delirium. The explanation for this may be the specific nature of the intensive care unit, the cardiac surgery department, and the surgical procedures, themselves. In conclusion, our research revealed that DSM–IV criteria for delirium were more inclusive than those of ICD–10. The cutoff score of 10 on the MDAS is suggested to be optimal in diagnosing delirium in the population of cardiac surgery patients.

REFERENCES

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1. Fox HN, Rizzo ND, Gifford S: Psychological observations of patients undergoing mitral surgery: a study of stress. Am Heart J 1954; 48:645–670[CrossRef][Medline]
2. Van der Mast RC: Postoperative delirium. Dement Geriatr Cogn Disord 1999; 10:401–405[CrossRef][Medline]
3. Bucerius J, Gummert JF, Borger MA, et al: Predictors of delirium after cardiac surgery delirium: effect of beating-heart (off-pump) surgery. J Thorac Cardiovasc Surg 2004; 127:57–64[Abstract/Free Full Text]
4. Kazmierski J, Kowman M, Banach M, et al: Preoperative predictors of delirium after cardiac surgery: a preliminary study. Gen Hosp Psychiatry 2006; 28:536–538[CrossRef][Medline]
5. Cole MG, Dendukuri N, McCusker J, et al: An empirical study of different diagnostic criteria for delirium among elderly medical inpatients. J Neuropsychiatry Clin Neurosci 2003; 15:200–207[Abstract/Free Full Text]
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7. American Psychiatric Association: Diagnostic and Statistical Manual of Mental Disorders, 4th Edition. Washington, DC, American Psychiatric Publishing, 1997
8. International Statistical Classification of Diseases and Health Related Problems, 10th Revision. The World Health Organization, 1993
9. Lawlor PG, Nekolaichuk C, Gargnon B, et al: Clinical utility, factor analysis, and further validation study of the Memorial Delirium Assessment Scale in patients with advanced cancer: assessing delirium in advanced cancer. Cancer 2000; 88:2859–2867[CrossRef][Medline]
10. Matsuoka Y, Miyake Y, Arakaki H, et al: Clinical utility and validation of the Japanese version of the Memorial Delirium Assessment Scale in a psychogeriatric inpatient setting. Gen Hosp Psychiatry 2001; 23:36–40[CrossRef][Medline]

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