Diagnostic Agreement on Delirium Between the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition; International Classification of Diseases, Tenth Revision; Confusion Assessment Method (CAM); and the Five‐Item CAM in Older Adults with Dementia

Abstract

We read with interest the article by Kreisel and colleagues,1 which showed excellent agreement between delirium diagnosed according to the four-item screening algorithm of the Confusion Assessment Method (CAM)2 and the criteria of delirium according to the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV)3 (sensitivity 74%, specificity 100%). Less agreement was found when the CAM was compared with the International Classification of Diseases, Tenth Revision (ICD-10)4 (sensitivity 82%, specificity 91%). By adding an extra requirement (abnormal psychomotor activity) to the CAM algorithm the authors introduced a new five-item “I-CAM” with much more favorable diagnostic and screening properties for detecting delirium according to the ICD-10 (sensitivity 91%, specificity 85%).1 The article inspired us to perform additional analyses on point prevalence data of adults aged 70 and older collected in 1999 to 2000 in acute hospitals in Helsinki, Finland (N = 81). The diagnostic agreement found between the CAM and fully operationalized criteria of delirium according to the DSM-IV and according to the clinical criteria of the ICD-10 was published in 2002.5 Sensitivity of 81% and specificity of 84% were found between the CAM and the DSM-IV, but although sensitivity remained stable (80%), specificity was only 63% when the CAM was compared with the ICD-10.5 No attempt was made to improve the latter inadequate agreement by adding additional items to the CAM. Neither was a comparison performed between the CAM and the formal diagnostic classifications in a subgroup of individuals with prior dementia. According to all available data,5 35 of the 81 individuals were found to have prior dementia. In this subgroup with dementia, the overlapping of delirium according to the CAM and the two formal diagnostic classifications are presented using sensitivity, specificity rates, and positive and negative predictive values of the diagnosis. As shown in Table 1, sensitivity between the CAM and either of the formal classifications was comparable with those that Thomas and colleagues presented,1 but specificity was considerably lower, especially when compared with the ICD-10. By adding an extra item of abnormal psychomotor behavior to the CAM, the sensitivity with the ICD-10 was improved, but only with the trade-off of less specificity. There might be several reasons for the discrepancy found between these two studies. First, although Thomas and colleagues used a neuropsychiatric-geriatric consensus panel (DSM-IV) and a geropsychiatrist with backup of a consensus panel (ICD-10) for their reference standards, the current study used full operationalization of each of the items included in these standards assessed by a geriatrician. Second, although a physician-in-training or a gerontologist assessed the CAM in Thomas and colleagues’ study, the current study used an experienced geriatrician. Finally, although Thomas and colleagues used the research criteria of the ICD-10, the current study used the clinical criteria, which are not identical. Overall, the analysis nevertheless supports the findings of Thomas and colleagues. The agreement between the CAM and the ICD-10 can be improved by adding an extra item, resulting in the I-CAM, but larger studies are needed to confirm the still-inadequate findings of these two small studies. Finally, for the benefit of future delirium research, the next editions of the DSM and the ICD should include an identical set of items for the diagnosis of delirium. Conflict of Interest: There are no financial conflicts of interest or personal conflict of interest relevant to the submitted manuscript for any authors. The original study was supported by La Carita Foundation, Uulo Arhio Foundation, the Academy of Finland (Grant 48613), and the Helsinki University Central Hospital. Author Contributions: Savikko N: Study concept and design, analysis and interpretation of data, preparation of manuscript. Pitkälä KH: Study design, acquisition of subjects and data, preparation of manuscript. Strandberg TE: Study design, interpretation of data, preparation of manuscript. Tilvis RS: Study design, preparation of manuscript. Laurila JV: Study concept and design, acquisition of subjects, acquisition and interpretation of data, preparation of manuscript. Sponsor's Role: There is no sponsor's role in the design, methods, subject recruitment, data collection, analysis, and preparation of this paper.