- Email: [email protected]
Japanese Version of the Delirium Rating Scale, Revised–98 (DRS-R98–J): Reliability and Validity
Japanese Version of the Delirium Rating Scale, Revised–98 (DRS-R98 –J): Reliability and Validity Masashi Kato, M.D., Yasuhiro Kishi, M.D. Toru Okuyama, M.D., Paula T. Trzepacz, M.D. Takashi Hosaka, M.D.
Background: Delirium is a common neuropsychiatric disorder in medical and surgical inpatients of all ages. It is associated with increased long-term mortality, longer length of hospital stay, poor functional recovery, and increased likelihood of nursing home placement. Objective: The aim of this study was to investigate the reliability and the validity of the Japanese translation of the Delirium Rating Scale, Revised–98 (DRS-R–98). Method: Psychiatric-consultation patients were assessed to compare groups of delirium, dementia, and non-delirium. Results: Mean Total and Severity scores significantly distinguished delirium from the other groups. The scale had high interrater reliability and high internal consistency. Mean Severity scores during delirium differed from the posttreatment scores. Stratum-specific likelihood ratios showed that the DRS-R98 –J is a reliable diagnostic tool. Conclusion: This study indicates that the Japanese version of the DRS-R-98 has high reliability and validity, and is a useful tool for assessing delirium among Japanese medically ill populations. (Psychosomatics 2010; 51:425– 431)
D
elirium is a common neuropsychiatric disorder in medical and surgical inpatients of all ages. It is associated with increased long-term mortality, longer length of hospital stay, poor functional recovery, and increased likelihood of nursing home placement.1–6 Delirium can be caused by many possible underlying medical and pharmacological etiologies that need to be elucidated and managed, although they are often underrecognized. Use of a validated instrument to detect and measure delirium severity can enhance more rapid recognition and treatment of delirium. The Delirium Rating Scale (DRS) is one of the most widely used delirium scales worldwide and has many translations, including Japanese.7 However, when used in serial ratings within an episode of delirium, the DRS is often modified to exclude certain items (e.g., onset of episode). Furthermore, the DRS has some limitations for use in phenomenological and treatment research because aspects of motor presentation and cognition are each cap-
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tured in a single item. Intending to address these shortcomings of the DRS, it was substantially revised, as the Delirium Rating Scale, Revised–98 (DRS-R-98).8 The DRS-R-98 also has anchored descriptors for each rated item-level, but it separates diagnostic items from symptom-severity items and has two items for motor presentation and five for cognition. Received December 15, 2008; revised March 3, 2009; accepted March 5, 2009. From the Dept. of Psychiatry and Behavioral Science, Tokai University School of Medicine, Isehara, Japan; the Ministry of Health, Labour and Welfare, Tokyo, Japan; the Dept. of Neuropsychiatry, Keio University School of Medicine, Tokyo, Japan; the Nippon Medical School, Musashikosugi Hospital, Kawasaki, Japan; Nagoya City University, Nagoya, Japan; the Dept. of Neurosciences, Lilly Research Laboratories, Indianapolis, IN; the Univ. of Mississippi Medical School, Jackson, MS; Tufts University School of Medicine, Boston, MA; Indiana University School of Medicine, Indianapolis, IN; and Tokyo Hospital, Tokai University School of Medicine, Tokyo, Japan. Send correspondence and reprint requests to Dr. Yasuhiro Kishi, Dept. of Psychiatry, Nippon Medical School Musashikosugi Hospital, 1-396 Kosugi-machi, Nakahara-ku, Kawasaki 211-8533 Japan. e-mail: [email protected]. © 2010 The Academy of Psychosomatic Medicine
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Japanese Version of the DRS–98 The DRS-R–98 is widely used worldwide, especially in treatment studies, with a dozen language translations and ongoing or completed revalidations of Dutch,9 Spanish,10,11 Korean,12 mainland and Taiwan Chinese,13 and Portuguese (Brazilian)14 versions. This study was designed to establish the psychometric properties of the Japanese translation of the DRS-R–98 (DRS-R98 –J). METHOD Study Population and Procedures A sample of 84 patients were consecutively referred to the psychiatric consultation service of Tokai University Hospital, in Kanagawa, Japan, between April 1, 2004 and March 31, 2005. They were divided into two groups for this study: delirium or non-delirium (including dementia). These diagnostic groups helped to assess the divergent validity of the scale. This study was approved by the Institutional Review Board at Tokai University. After obtaining informed consent from study participants (when they regained mental capacity) or their proxy, one psychiatrist (MK) rated patients with the DRS-R98 –J, while a second psychiatrist (TO) made the DSM-IV–TR psychiatric diagnoses on the basis of the consultation interview and administered the Mini-Mental State Exam (MMSE),15 the Clinical Global Impression–Severity Scale for Delirium (CGI-S–D),16 and the Eastern Cooperative Oncology Group Performance Status (ECOG–PS).17 These scales were blindly assessed by the raters. In order to assess interrater reliability, a third psychiatrist (YK) independently rated a subset of the same subjects (N⫽20) while blinded to diagnosis and scores of the other rater. The raters in this study were already fully trained on the scale and quite experienced in its use. Therefore, we decided that only a small subsample was needed to reevaluate the consistency across raters. To assess the DRSR98 –J’s ability to measure change in severity over time, the delirium patients were compared between pre- and post-treatment; 13 patients’ initial DRS-R98 –J severity scores, the MMSE, and the CGI-S–D were compared with scores after treatment when they no longer met standards for delirium by DSM-IV criteria. Rating Scales Delirium Rating Scale, Revised–98 (DRS-R-98) The DRS-R-98 is a 16-item, clinician-rated scale, with anchored item-descriptions corresponding to both 426
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symptoms and temporal aspects of delirium.8 The Severity scale has 13 items, each rated from 0 to 3, where the sum has a maximum of 39 points, and where higher scores indicate greater severity of delirium. Three additional items (rated from 0 to either 2 or 3) capture temporal course and attribution to an underlying etiology, and, when added to the sum of the 13 symptom-items, produce the DRS-R-98 Total score, which ranges from 0 to 46. The original validation study suggested cutoff scores for differential diagnosis of around 17–18 points on the Total scale and around 15 for the Severity scale.8 However, milder forms of delirium can occur with scores ⱖ11.8 An experienced consultation–liaison psychiatrist (YK) had translated the DRS-R-98 into Japanese with the author’s permission and produced forward- and backtranslations to create the Japanese version of the DRSR-98 (DRS-R98 –J),18 which is the version used in this study. Mini-Mental State Exam (MMSE) The MMSE15 is a widely used reliable and valid means of assessing generalized cognitive dysfunction as it occurs in delirium or dementia, and it has been validated in Japanese subjects.19 MMSE scores range from 0 to 30, where a cutoff score of ⱕ23 indicates significant cognitive impairment. This scale helped to evaluate convergent validity, given that cognition is an important component of delirium. The Eastern Cooperative Oncology Group Performance Status (ECOG PS) Patients’ daily-living ability performance status was assessed with the Eastern Cooperative Oncology Group Performance Status (ECOG PS).17 The ECOG PS scale is a one-item scale, and it ranges from 0 to 4, with higher scores indicating more difficulty with activities of daily living. Although constructed for use in oncology patients, it has been applied to broader medically ill patient populations to assess the severity of their physical condition. The Clinical Global Impression Severity Scale for Delirium (CGI-S–D) Overall severity of delirium was also assessed with the CGI-S–D scale,16 which captures global severity on the basis of the clinician’s experience with delirium patients in general. The CGI-S–D is scored as a single overall impression of illness severity on a Likert-type scale ranging from 1 to 7, Psychosomatics 51:5, September-October 2010
Kato et al. where 1 is normal or not ill at all, and 7 is extremely ill. This scale provided a source of convergent validity.
TABLE 1.
Demographic and Rating Scale Scores Between the Delirium and Non-Delirium Group
Statistical Analysis Data were analyzed using SPSS 12.0-J software. For comparison of parametric data in two groups, appropriate two-sample t-tests were performed, depending on whether variances were equal or unequal by Levene’s test. The chi-square test was used to compare categorical data. When sample sizes were prohibitively small, we used Fisher’s exact test. The internal consistency or homogeneity coefficient for the DRS-R98 –J was calculated with Cronbach’s ␣. Concurrent validity was calculated with Pearson correlations between scales. Interrater reliability was measured by intraclass correlation coefficient (ICC) for pairs of the independent raters. Cutoff scores for the DRS-R-98 –J were determined by using receiver-operator characteristic (ROC) analyses to determine acceptable levels of sensitivity and specificity when comparing the delirium group with all non-delirium subjects. The SSLRs (stratum-specific likelihood ratios) were also calculated. The SSLR is an expression of the odds (odds ⫽ probability/1-minus-probability) that a positive test result will be obtained in an actual case. When the pretest odds of the target condition is known, the SSLR can be used to calculate the posttest odds of the condition actually being present, given a positive test. To calculate the SSLR, we used the following website (http://www.ebpcenter.com/). In general, an SSLR over 10 makes the target disorder highly probable, whereas one smaller than 0.1 usually rules it out.20,21 Those between 5 and 10 or between 0.1 and 0.2 are often very informative. Those between 0.5 and 2 would be of little assistance in the diagnosis.20,21 RESULTS Of the 84 patients, 3 refused to participate in the study, leaving 81 who were categorized into either the delirium (N⫽48) or non-delirium group (N⫽33). The non-delirium group’s psychiatric diagnoses were the following: dementia: 8; adjustment disorder: 7; sleep disorder: 6; schizophrenia: 4; major depression: 2; anxiety disorder: 1; somatoform disorder: 1; and no psychiatric diagnosis: 4. The most frequent primary underlying physical conditions were cancer (N⫽60; 74.1%), infectious diseases (N⫽3; 3.7%), neurological diseases (N⫽3; 3.7%), heart disease (N⫽3; 3.7%), and injuries (N⫽3; 3.7%); 3 of the 8 dementia patients also had another psychiatric diagnosis, such as anxiety disorder. Psychosomatics 51:5, September-October 2010
Age, years Sex, male, N (%) DRS-R-98–J: Total DRS-R-98–J: Severity MMSE ECOG PS CGI-S-D
Delirium (Nⴝ48)
Non-Delirium (Nⴝ33)
Dementia (Nⴝ8)
68.5 (14.0) 35 (72.9)
57.7 (14.0)** 21 (63.6)
56.1 (14.8)* 4 (50.0)
24.6 (6.8)
7.0 (4.9)**
12.1 (5.8)**
20.1 (6.7) 16.1 (7.1) 2.8 (1.1) 5.5 (0.7)
5.5 (4.2)** 24.6 (4.0)** 1.7 (1.4)** 1.0 (0.0)**
10.2 (5.5)** 20.3 (4.2) 2.0 (1.7) 1.0 (0.0)**
The dementia subgroup is a subset of the non-delirium group. Data are expressed as mean (standard deviation) except for where otherwise indicated. ** p⬍0.01 vs. Delirium; * p⬍0.05 vs. Delirium.
Table 1 shows the demographic and rating-scale scores for the delirium, non-delirium, and dementia groups (the dementia group is a subset of the nondelirium group). The delirium patients were significantly older than the nondelirium and had numerically more men. The delirium group had significantly worse mean scores on the DRS-R98 –J Total and Severity and the CGI-S–D scales than the non-delirium group and the dementia subgroup. Although MMSE and ECOG PS scores were most impaired in the delirium group, they were only significantly different from the non-delirium group, and not the dementia subgroup. Figure 1 shows boxplot distributions of scores comparing across groups classified by the DSM-IV–TR psychiatric diagnoses (median and quartiles) for DRS-R–98 total and severity, MMSE and ECOG PS. The delirium group was significantly more impaired than the non-delirium group on all scales, and the dementia group on DRSR98 –J scales, although the overlap with the dementia group was least on the DRS-R98 –J scales. There was a strong correlation between the DRS-R98 –J and the MMSE, indicating a reasonable concurrentvalidity relationship between severity of symptoms as measured by the DRS-R-98 –J and level of cognitive impairment as measured by the MMSE, even though the DRS-R-98 –J measures symptoms more broadly than the cognition component (DRS-R-98 –J Total: r ⫽ – 0.814; p⬍0.001; and DRS-R-98 –J Severity: r ⫽ – 0.840; p⬍0.001). The DRS-R-98 –J strongly correlated with the CGI-S–D (DRS-R-98 –J Total: r⫽0.788; p⬍0.001) and DRS-R-98 –J Severity: r⫽0.799; p⬍0.001), also supporting concurrent validity. http://psy.psychiatryonline.org
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Japanese Version of the DRS–98
FIGURE 1.
Boxplots of DRS-R98 –J Total and Severity Scores, MMSE, and ECOGPS Scores for the Delirium and Non-Delirium Groups and the Dementia Subgroup
TABLE 3.
Internal Consistency of the DRS-R98 –J Severity Scale and Total Scale (Cronbach’s ␣)
␣ Coefficients
DRS-R98-J Total Scores
40 30 20 10
DRS-R98-J Severity Scores
0
Delirium (N=48)
Non-Delirium (N=33)
Dementia (N=8)
40 30 20
Severity Scale
Total Scale
1. Sleep–wake cycle disturbance 2. Perceptual disturbances and hallucinations 3. Delusions 4. Lability of affect 5. Language 6. Thought-process abnormalities 7. Motor agitation 8. Motor retardation 9. Orientation 10. Attention 11. Short-term memory 12. Long-term memory 13. Visuospatial ability 14. Temporal onset of symptoms 15. Fluctuation of symptom severity 16. Physical disorder Total Scale Cronbach’s
0.90 0.91 0.90 0.90 0.89 0.88 0.90 0.90 0.89 0.89 0.90 0.89 0.89 — — — 0.90
0.91 0.92 0.91 0.91 0.91 0.90 0.91 0.92 0.91 0.91 0.91 0.91 0.91 0.91 0.91 0.91 0.92
Coefficients for items correspond to scale’s ␣ if this item is deleted.
*
10 0
Delirium (N=48)
TABLE 2.
Non-Delirium (N=33)
Dementia (N=8)
Pre- and Post-Treatment Scores in a Delirium Subgroup (Nⴝ13)
Scale
Pre-Treatment
Post-Treatment
DRS-R98–J Severity* MMSE* CGI-S–D*
19.3 (5.7) 18.2 (5.2) 5.3 (0.6)
5.4 (3.0) 23.3 (3.3) 1.4 (0.5)
Values are mean (standard deviation). DRS-R98 –J: Delirium Rating Scale, 1998 Revision–Japanese version; MMSE: Mini-Mental State Exam; CGI-S–D: Clinical Global Impression Scale for Delirium. * p⬍0.001.
A group of 13 delirium patients were reassessed after treatment, when they no longer met DSM-IV–TR criteria for delirium. Mean scores for DRS-R-98 –J Severity scores, MMSE, and CGI-S–D (Table 2) were all significantly improved in the non-delirium state (p⬍0.001), and essentially in the normal range. Internal consistency was high, with Cronbach’s ␣ coefficient for the DRS-R98 –J Total at 0.92 and DRS-R98 –J 428
DRS-R-98–J Items
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Severity at 0.90. The ␣ coefficient, corrected for the effect of removing each item from the scale, ranged from 0.90 to 0.92 for the DRS-R98 –J Total and 0.89 to 0.91 for the Severity scale (Table 3). The ICC between the two independent raters was very high for the DRS-R-98 –J Total: 0.99, and the DRS-R98 –J Severity: 0.99. ROC analyses were performed for DRS-R-98 –J scores, comparing delirium to non-delirium and dementia groups. Table 4 shows sensitivity and specificity for ROC analysis at various cutoff scores for the DRS-R-98 –J Total and Severity scales. Compared with the nondelirium group, the best cutoff score for the DRS-R-98 –J Total scale was 14.5, resulting in 98% sensitivity and 94% specificity, and for the DRS-R-98 –J Severity scale was 10.0, resulting in 98% sensitivity and 91% specificity. ROC analyses comparing delirium versus dementia, found that the best cutoff score for the DRS-R98 –J Total scale was 14.5, with 98% sensitivity and 75% specificity, and for the DRS-R-98 –J Severity scale was 11.5, resulting in 92% sensitivity and 75% specificity. Table 5 shows the SSLR of the DRS-R-98 –J Total scale for delirium. Scores of the DRS-R-98 –J Total scale between 12 and 15 would be of little assistance in delirium diagnosis. Psychosomatics 51:5, September-October 2010
Kato et al.
TABLE 4.
Sensitivity and Specificity of the DRS-R98 –J Total and Severity Scales, Based on Receiver Operating Characteristics (ROC) Analysis; Delirium vs. NonDelirium Groups, and Dementia Subgroup
Delirium vs. Non-Delirium Cutoff Score
Sensitivity (%)
Specificity (%)
10.5 13.5 14.5 15.5 16.5 20.5 21.5 5.5 8.5 10.0 11.5 13.5 17.5 20.5
100 98 98 94 88 69 65 100 98 98 92 83 60 44
82 91 94 94 94 97 100 70 85 91 94 94 97 100
Cutoff Score
Sensitivity (%)
Specificity (%)
10.5 12.5 14.5 15.5 18.5 20.5 21.5 5.3 8.0 10.0 11.5 13.5 17.5 20.5
100 98 98 94 82 69 65 100 98 98 92 83 60 44
50 63 75 75 75 88 100 13 50 63 75 75 88 100
Total Score
Severity Score
Delirium vs. Dementia
Total Score
Severity Score
TABLE 5.
Stratum-Specific Likelihood Ratios (SSLRs) of the DRS-R98 –J Total Scale for Delirium, Comparing Delirium and Non-Delirium Groups
Scores
Delirium
Non-Delirium
SSLR
95% Confidence Interval
0–11 12–15 16–20 ⱖ21
1 2 12 33
29 2 1 1
0.02 0.69 8.25 22.69
0.00–0.12 0.13–3.75 1.60–42.33 4.69–109.64
DISCUSSION This study indicates that the Japanese version of the DRSR-98 has high reliability and validity, and is a useful tool for assessing delirium among Japanese medically-ill popPsychosomatics 51:5, September-October 2010
ulations. DRS-R98 –J items have a high level of internal consistency, interrater reliability between two psychiatrists, concurrent validity with the MMSE and CGI-S-D delirium severity, and ability to detect change over time. The DRS-R-98 was developed primarily as an instrument for assessing the severity of delirium symptoms in serial ratings, in addition to use as a diagnostic tool, and this aim is supported by our results in Japanese patients. The DRS-R98 –J significantly differentiated between hospitalized patients with and without delirium, including those with dementia, using a total scale cutoff score of 14.5. This cutoff score is identical to the Colombian adaptation of the Spanish version (cutoff score is 14)11 and the Chinese version (cutoff scores is 15.5).13 However, the cutoff score of 14.5 on the DRS-R98 –J Total scale was lower than that in the original study (17.75),8 the Portuguese version (20.0),22 and the Korean study (21.5),12 possibly because of the greater severity of dementia in those studies that drive the cutoff score higher for differential diagnosis purposes.22 Patients with dementia in this study had only mild severity, as based on the mean MMSE of 20.3. Our delirium patients had somewhat lower mean DRS-R-98 scores than the original or Portuguese study.8,22 Our non-delirium group might also have lower psychiatric severity than other studies, given that we included four patients without Axis I psychiatric disorder and six patients with sleep disorder as a primary psychiatric illness; however, the DRS-R-98 score in our non-delirium group was close to the original DRS-R-98 report for schizophrenia (7.7), depression (7.0), and other groups (8.9). However, the mean total scale score in our non-delirium group, excluding the dementia patients, was 5.3, lower than in the original study. Cross-cultural differences in expression or rating of symptoms may also partially explain the groups’ scores being lower. Several clinical epidemiologists have recently criticized the use of the fixed cutoff thresholds, and have advocated multilevel or stratum-specific likelihood ratios (SSLRs).21 The SSLR approach has several advantages.21,23 It nicely incorporates the differences in pretest probabilities between populations and illustrates in clearer terms what we should do in the diagnostic processes of an individual or a group of individuals. A useful nomogram proposed by Fagan facilitates the translation of SSLRs into predicted probabilities.21,23,24 Furthermore, in the case of a continuous scale such as the DRS-R-98, SSLR retains more information than that given by a single cutoff and sensitivity and specificity approach. For example, given a patient whose pretest probability of delirium is 50% (clinhttp://psy.psychiatryonline.org
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Japanese Version of the DRS–98 ically uncertain), and he or she scores a total DRS-R98 –J score of 21, this provides an approximately 96% posttest probability. On the other hand, given another patient, whose pretest probability of delirium is 50% (clinically uncertain), and he or she scores a total DRS-R98 –J score of 11, this provides an approximately 1% posttest probability. This study showed that only 4.9% of the study participants had noninformative SSLRs (i.e., 4 out of the 81 patients had scores between 13 and 16), suggesting that this scale is a very useful clinical diagnostic tool. For example, given a patient whose pretest probability of delirium is 40% (clinically uncertain) and he or she scores a total DRS-R-98 –J score of 14 (around the cutoff score based on the ROC), this provides an approximately 32% posttest probability, which would not provide benefit in terms of changing the pre- and posttest diagnosis (i.e., differential diagnoses are difficult, and further observational clinical work should be necessary). It is important to acknowledge the methodological limitations of the study. First, over 70% of the underlying physical conditions of the study participants had cancer. Thus, the findings may not be applicable to all
medical and surgical patients. Several studies, however, show that the DRS-R-98 is proven to be valid in various medical and surgical conditions.8 –13 Second, the sample size of dementia was small (N⫽8) in this study. Furthermore, standardized psychiatric scales and structured clinical interviews were not used in the non-delirium patients. Further studies, with larger dementia sample sizes might be necessary to reassess the dementia and delirium groups. It would also be useful in assessing delirium superimposed on dementia. CONCLUSION The Japanese version of the DRS-R-98, the DRS-R-98 –J, appears to be a valid and reliable measure of delirium, not only assessing its severity but also its diagnosis. This scale can be used clinically to monitor the course of illness when administered serially. Its sufficient breadth of phenomenology offers research applications, as well. This work was presented as a poster at the Annual Meeting of the Academy of Psychosomatic Medicine, November 2005, Santa Ana Pueblo, NM.
References 1. Pitkala KH, Laurila JV, Strandberg TE, et al: Prognostic significance of delirium in frail older people. Dement Geriatr Cogn Disord 2005; 19:158 –163 2. Marcantonio ER, Flacker JM, Michaels M, et al: Delirium is independently associated with poor functional recovery after hip fracture. J Am Geriatr Soc 2000; 48:618 – 624 3. Inouye SK, Rushing JT, Foreman MD, et al: Does delirium contribute to poor hospital outcomes? a three-site epidemiologic study. J Gen Intern Med 1998; 13:234 –242 4. Francis J, Martin D, Kapoor WN: A prospective study of delirium in hospitalized elderly. JAMA 1990; 263:1097–1101 5. Schor JD, Levkoff SE, Lipsitz LA, et al: Risk factors for delirium in hospitalized elderly. JAMA 1992; 267:827– 831 6. Kishi Y, Iwasaki Y, Takezawa K, et al: Delirium in critical-careunit patients admitted through an emergency room. Gen Hosp Psychiatry 1995; 17:371–379 7. Trzepacz PT, Baker RW, Greenhouse J: A symptom rating scale for delirium. Psychiatry Res 1988; 23:89 –97 8. Trzepacz PT, Mittal D, Torres R, et al: Validation of the Delirium Rating Scale, Revised 98: comparison with the Delirium Rating Scale and the Cognitive Test for Delirium. J Neuropsychiatry Clin Neurosci 2001; 13:229 –242 9. de Rooij SE, van Munster BC, Korevaar JC, et al: Delirium subtype identification and the validation of the Delirium Rating Scale, Revised–98 (Dutch version) in hospitalized elderly patients. Int J Geriatr Psychiatry 2006; 21:876 – 882 10. Fonseca F, Bulbena A, Navarrete R, et al: Spanish version of the Delirium Rating Scale, Revised–98: reliability and validity. J Psychosom Res 2005; 59:147–151
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11. Franco JG, Mejia MA, Ochoa SB, et al: [Delirium Rating Scale, Revised–98 (DRS-R-98): Colombian Adaptation of the Spanish Version]. Actas Esp Psiquiatr 2007; 35:170 –175 12. Lim KO, Kim SY, Lee YH, et al: A validation study for the Korean Version of the Delirium Rating Scale, Revised–98 (KDRS-98). J Korean Neuropsychiatr Assoc 2006; 45:518 –526 13. Huang MC, Lee CH, Lai YC, et al: Chinese Version of the Delirium Rating Scale, Revised–98: reliability and validity. Compr Psychiatry 2009; 50:81– 85 14. de Negreiros DP, da Silva Meleiro AM, Furlanetto LM, et al: Trzepacz part Portuguese Version of the Delirium Rating Scale, Revised–98: reliability and validity. Int J Geriatr Psychiatry 2008; 23:472– 477 15. 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 16. Guy W: ECDEU Assessment Manual for Psychopharmacology. Rockville, MD, U.S. Dept. of Health and Human Services, 1976. Report number: Publ No ADM 76 –338 17. Oken MM, Creech RH, Tormey DC, et al: Toxicity and response criteria of the Eastern Cooperative Oncology Group. Am J Clin Oncol 1982; 5:649 – 655 18. Trzepacz P, Kishi Y, Hosaka T, et al: Japanese Version of the Delirium Rating Scale, Revised–98. Seishinigaku 2001; 43:1365–1371 (in Japanese) 19. Mori E, Mitani Y, Yamadori A: The validity of Japanese Version of Mini-Mental State Exam in patients with nervous disorder. Shinkei Shinri 1985; 1:2–10 20. Jaeschke R, Guyatt GH, Sackett DL: Users’ Guides to the Med-
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Kato et al. ical Literature, III: how to use an article about a diagnostic test, B: what are the results, and will they help me in caring for my patients? The Evidence-Based Medicine Working Group. JAMA 1994; 271:703–707 21. Furukawa TA, Goldberg DP, Rabe-Hesketh S, et al: Stratumspecific likelihood ratios of two versions of the General Health Questionnaire. Psychol Med 2001; 31:519 –529 22. Negreiros DP, Meleiro AM, Furlanetto LM, et al: Portuguese
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Version of the Delirium Rating Scale, Revised–98: reliability and validity. Int J Geriatr Psychiatry 2008; 23:472– 477 23. Furukawa TA, Andrews G, Goldberg DP: Stratum-specific likelihood ratios of the General Health Questionnaire in the community: help-seeking and physical comorbidity affect the test characteristics. Psychol Med 2002; 32:743–748 24. Fagan TJ: Nomogram for Bayes’ theorem (letter). N Engl J Med 1975; 293:257
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Background: Delirium is a common neuropsychiatric disorder in medical and surgical inpatients of all ages. It is associated with increased long-term mortality, longer length of hospital stay, poor functional recovery, and increased likelihood of nursing home placement. Objective: The aim of this study was to investigate the reliability and the validity of the Japanese translation of the Delirium Rating Scale, Revised–98 (DRS-R–98). Method: Psychiatric-consultation patients were assessed to compare groups of delirium, dementia, and non-delirium. Results: Mean Total and Severity scores significantly distinguished delirium from the other groups. The scale had high interrater reliability and high internal consistency. Mean Severity scores during delirium differed from the posttreatment scores. Stratum-specific likelihood ratios showed that the DRS-R98 –J is a reliable diagnostic tool. Conclusion: This study indicates that the Japanese version of the DRS-R-98 has high reliability and validity, and is a useful tool for assessing delirium among Japanese medically ill populations. (Psychosomatics 2010; 51:425– 431)
D
elirium is a common neuropsychiatric disorder in medical and surgical inpatients of all ages. It is associated with increased long-term mortality, longer length of hospital stay, poor functional recovery, and increased likelihood of nursing home placement.1–6 Delirium can be caused by many possible underlying medical and pharmacological etiologies that need to be elucidated and managed, although they are often underrecognized. Use of a validated instrument to detect and measure delirium severity can enhance more rapid recognition and treatment of delirium. The Delirium Rating Scale (DRS) is one of the most widely used delirium scales worldwide and has many translations, including Japanese.7 However, when used in serial ratings within an episode of delirium, the DRS is often modified to exclude certain items (e.g., onset of episode). Furthermore, the DRS has some limitations for use in phenomenological and treatment research because aspects of motor presentation and cognition are each cap-
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tured in a single item. Intending to address these shortcomings of the DRS, it was substantially revised, as the Delirium Rating Scale, Revised–98 (DRS-R-98).8 The DRS-R-98 also has anchored descriptors for each rated item-level, but it separates diagnostic items from symptom-severity items and has two items for motor presentation and five for cognition. Received December 15, 2008; revised March 3, 2009; accepted March 5, 2009. From the Dept. of Psychiatry and Behavioral Science, Tokai University School of Medicine, Isehara, Japan; the Ministry of Health, Labour and Welfare, Tokyo, Japan; the Dept. of Neuropsychiatry, Keio University School of Medicine, Tokyo, Japan; the Nippon Medical School, Musashikosugi Hospital, Kawasaki, Japan; Nagoya City University, Nagoya, Japan; the Dept. of Neurosciences, Lilly Research Laboratories, Indianapolis, IN; the Univ. of Mississippi Medical School, Jackson, MS; Tufts University School of Medicine, Boston, MA; Indiana University School of Medicine, Indianapolis, IN; and Tokyo Hospital, Tokai University School of Medicine, Tokyo, Japan. Send correspondence and reprint requests to Dr. Yasuhiro Kishi, Dept. of Psychiatry, Nippon Medical School Musashikosugi Hospital, 1-396 Kosugi-machi, Nakahara-ku, Kawasaki 211-8533 Japan. e-mail: [email protected]. © 2010 The Academy of Psychosomatic Medicine
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Japanese Version of the DRS–98 The DRS-R–98 is widely used worldwide, especially in treatment studies, with a dozen language translations and ongoing or completed revalidations of Dutch,9 Spanish,10,11 Korean,12 mainland and Taiwan Chinese,13 and Portuguese (Brazilian)14 versions. This study was designed to establish the psychometric properties of the Japanese translation of the DRS-R–98 (DRS-R98 –J). METHOD Study Population and Procedures A sample of 84 patients were consecutively referred to the psychiatric consultation service of Tokai University Hospital, in Kanagawa, Japan, between April 1, 2004 and March 31, 2005. They were divided into two groups for this study: delirium or non-delirium (including dementia). These diagnostic groups helped to assess the divergent validity of the scale. This study was approved by the Institutional Review Board at Tokai University. After obtaining informed consent from study participants (when they regained mental capacity) or their proxy, one psychiatrist (MK) rated patients with the DRS-R98 –J, while a second psychiatrist (TO) made the DSM-IV–TR psychiatric diagnoses on the basis of the consultation interview and administered the Mini-Mental State Exam (MMSE),15 the Clinical Global Impression–Severity Scale for Delirium (CGI-S–D),16 and the Eastern Cooperative Oncology Group Performance Status (ECOG–PS).17 These scales were blindly assessed by the raters. In order to assess interrater reliability, a third psychiatrist (YK) independently rated a subset of the same subjects (N⫽20) while blinded to diagnosis and scores of the other rater. The raters in this study were already fully trained on the scale and quite experienced in its use. Therefore, we decided that only a small subsample was needed to reevaluate the consistency across raters. To assess the DRSR98 –J’s ability to measure change in severity over time, the delirium patients were compared between pre- and post-treatment; 13 patients’ initial DRS-R98 –J severity scores, the MMSE, and the CGI-S–D were compared with scores after treatment when they no longer met standards for delirium by DSM-IV criteria. Rating Scales Delirium Rating Scale, Revised–98 (DRS-R-98) The DRS-R-98 is a 16-item, clinician-rated scale, with anchored item-descriptions corresponding to both 426
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symptoms and temporal aspects of delirium.8 The Severity scale has 13 items, each rated from 0 to 3, where the sum has a maximum of 39 points, and where higher scores indicate greater severity of delirium. Three additional items (rated from 0 to either 2 or 3) capture temporal course and attribution to an underlying etiology, and, when added to the sum of the 13 symptom-items, produce the DRS-R-98 Total score, which ranges from 0 to 46. The original validation study suggested cutoff scores for differential diagnosis of around 17–18 points on the Total scale and around 15 for the Severity scale.8 However, milder forms of delirium can occur with scores ⱖ11.8 An experienced consultation–liaison psychiatrist (YK) had translated the DRS-R-98 into Japanese with the author’s permission and produced forward- and backtranslations to create the Japanese version of the DRSR-98 (DRS-R98 –J),18 which is the version used in this study. Mini-Mental State Exam (MMSE) The MMSE15 is a widely used reliable and valid means of assessing generalized cognitive dysfunction as it occurs in delirium or dementia, and it has been validated in Japanese subjects.19 MMSE scores range from 0 to 30, where a cutoff score of ⱕ23 indicates significant cognitive impairment. This scale helped to evaluate convergent validity, given that cognition is an important component of delirium. The Eastern Cooperative Oncology Group Performance Status (ECOG PS) Patients’ daily-living ability performance status was assessed with the Eastern Cooperative Oncology Group Performance Status (ECOG PS).17 The ECOG PS scale is a one-item scale, and it ranges from 0 to 4, with higher scores indicating more difficulty with activities of daily living. Although constructed for use in oncology patients, it has been applied to broader medically ill patient populations to assess the severity of their physical condition. The Clinical Global Impression Severity Scale for Delirium (CGI-S–D) Overall severity of delirium was also assessed with the CGI-S–D scale,16 which captures global severity on the basis of the clinician’s experience with delirium patients in general. The CGI-S–D is scored as a single overall impression of illness severity on a Likert-type scale ranging from 1 to 7, Psychosomatics 51:5, September-October 2010
Kato et al. where 1 is normal or not ill at all, and 7 is extremely ill. This scale provided a source of convergent validity.
TABLE 1.
Demographic and Rating Scale Scores Between the Delirium and Non-Delirium Group
Statistical Analysis Data were analyzed using SPSS 12.0-J software. For comparison of parametric data in two groups, appropriate two-sample t-tests were performed, depending on whether variances were equal or unequal by Levene’s test. The chi-square test was used to compare categorical data. When sample sizes were prohibitively small, we used Fisher’s exact test. The internal consistency or homogeneity coefficient for the DRS-R98 –J was calculated with Cronbach’s ␣. Concurrent validity was calculated with Pearson correlations between scales. Interrater reliability was measured by intraclass correlation coefficient (ICC) for pairs of the independent raters. Cutoff scores for the DRS-R-98 –J were determined by using receiver-operator characteristic (ROC) analyses to determine acceptable levels of sensitivity and specificity when comparing the delirium group with all non-delirium subjects. The SSLRs (stratum-specific likelihood ratios) were also calculated. The SSLR is an expression of the odds (odds ⫽ probability/1-minus-probability) that a positive test result will be obtained in an actual case. When the pretest odds of the target condition is known, the SSLR can be used to calculate the posttest odds of the condition actually being present, given a positive test. To calculate the SSLR, we used the following website (http://www.ebpcenter.com/). In general, an SSLR over 10 makes the target disorder highly probable, whereas one smaller than 0.1 usually rules it out.20,21 Those between 5 and 10 or between 0.1 and 0.2 are often very informative. Those between 0.5 and 2 would be of little assistance in the diagnosis.20,21 RESULTS Of the 84 patients, 3 refused to participate in the study, leaving 81 who were categorized into either the delirium (N⫽48) or non-delirium group (N⫽33). The non-delirium group’s psychiatric diagnoses were the following: dementia: 8; adjustment disorder: 7; sleep disorder: 6; schizophrenia: 4; major depression: 2; anxiety disorder: 1; somatoform disorder: 1; and no psychiatric diagnosis: 4. The most frequent primary underlying physical conditions were cancer (N⫽60; 74.1%), infectious diseases (N⫽3; 3.7%), neurological diseases (N⫽3; 3.7%), heart disease (N⫽3; 3.7%), and injuries (N⫽3; 3.7%); 3 of the 8 dementia patients also had another psychiatric diagnosis, such as anxiety disorder. Psychosomatics 51:5, September-October 2010
Age, years Sex, male, N (%) DRS-R-98–J: Total DRS-R-98–J: Severity MMSE ECOG PS CGI-S-D
Delirium (Nⴝ48)
Non-Delirium (Nⴝ33)
Dementia (Nⴝ8)
68.5 (14.0) 35 (72.9)
57.7 (14.0)** 21 (63.6)
56.1 (14.8)* 4 (50.0)
24.6 (6.8)
7.0 (4.9)**
12.1 (5.8)**
20.1 (6.7) 16.1 (7.1) 2.8 (1.1) 5.5 (0.7)
5.5 (4.2)** 24.6 (4.0)** 1.7 (1.4)** 1.0 (0.0)**
10.2 (5.5)** 20.3 (4.2) 2.0 (1.7) 1.0 (0.0)**
The dementia subgroup is a subset of the non-delirium group. Data are expressed as mean (standard deviation) except for where otherwise indicated. ** p⬍0.01 vs. Delirium; * p⬍0.05 vs. Delirium.
Table 1 shows the demographic and rating-scale scores for the delirium, non-delirium, and dementia groups (the dementia group is a subset of the nondelirium group). The delirium patients were significantly older than the nondelirium and had numerically more men. The delirium group had significantly worse mean scores on the DRS-R98 –J Total and Severity and the CGI-S–D scales than the non-delirium group and the dementia subgroup. Although MMSE and ECOG PS scores were most impaired in the delirium group, they were only significantly different from the non-delirium group, and not the dementia subgroup. Figure 1 shows boxplot distributions of scores comparing across groups classified by the DSM-IV–TR psychiatric diagnoses (median and quartiles) for DRS-R–98 total and severity, MMSE and ECOG PS. The delirium group was significantly more impaired than the non-delirium group on all scales, and the dementia group on DRSR98 –J scales, although the overlap with the dementia group was least on the DRS-R98 –J scales. There was a strong correlation between the DRS-R98 –J and the MMSE, indicating a reasonable concurrentvalidity relationship between severity of symptoms as measured by the DRS-R-98 –J and level of cognitive impairment as measured by the MMSE, even though the DRS-R-98 –J measures symptoms more broadly than the cognition component (DRS-R-98 –J Total: r ⫽ – 0.814; p⬍0.001; and DRS-R-98 –J Severity: r ⫽ – 0.840; p⬍0.001). The DRS-R-98 –J strongly correlated with the CGI-S–D (DRS-R-98 –J Total: r⫽0.788; p⬍0.001) and DRS-R-98 –J Severity: r⫽0.799; p⬍0.001), also supporting concurrent validity. http://psy.psychiatryonline.org
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Japanese Version of the DRS–98
FIGURE 1.
Boxplots of DRS-R98 –J Total and Severity Scores, MMSE, and ECOGPS Scores for the Delirium and Non-Delirium Groups and the Dementia Subgroup
TABLE 3.
Internal Consistency of the DRS-R98 –J Severity Scale and Total Scale (Cronbach’s ␣)
␣ Coefficients
DRS-R98-J Total Scores
40 30 20 10
DRS-R98-J Severity Scores
0
Delirium (N=48)
Non-Delirium (N=33)
Dementia (N=8)
40 30 20
Severity Scale
Total Scale
1. Sleep–wake cycle disturbance 2. Perceptual disturbances and hallucinations 3. Delusions 4. Lability of affect 5. Language 6. Thought-process abnormalities 7. Motor agitation 8. Motor retardation 9. Orientation 10. Attention 11. Short-term memory 12. Long-term memory 13. Visuospatial ability 14. Temporal onset of symptoms 15. Fluctuation of symptom severity 16. Physical disorder Total Scale Cronbach’s
0.90 0.91 0.90 0.90 0.89 0.88 0.90 0.90 0.89 0.89 0.90 0.89 0.89 — — — 0.90
0.91 0.92 0.91 0.91 0.91 0.90 0.91 0.92 0.91 0.91 0.91 0.91 0.91 0.91 0.91 0.91 0.92
Coefficients for items correspond to scale’s ␣ if this item is deleted.
*
10 0
Delirium (N=48)
TABLE 2.
Non-Delirium (N=33)
Dementia (N=8)
Pre- and Post-Treatment Scores in a Delirium Subgroup (Nⴝ13)
Scale
Pre-Treatment
Post-Treatment
DRS-R98–J Severity* MMSE* CGI-S–D*
19.3 (5.7) 18.2 (5.2) 5.3 (0.6)
5.4 (3.0) 23.3 (3.3) 1.4 (0.5)
Values are mean (standard deviation). DRS-R98 –J: Delirium Rating Scale, 1998 Revision–Japanese version; MMSE: Mini-Mental State Exam; CGI-S–D: Clinical Global Impression Scale for Delirium. * p⬍0.001.
A group of 13 delirium patients were reassessed after treatment, when they no longer met DSM-IV–TR criteria for delirium. Mean scores for DRS-R-98 –J Severity scores, MMSE, and CGI-S–D (Table 2) were all significantly improved in the non-delirium state (p⬍0.001), and essentially in the normal range. Internal consistency was high, with Cronbach’s ␣ coefficient for the DRS-R98 –J Total at 0.92 and DRS-R98 –J 428
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Severity at 0.90. The ␣ coefficient, corrected for the effect of removing each item from the scale, ranged from 0.90 to 0.92 for the DRS-R98 –J Total and 0.89 to 0.91 for the Severity scale (Table 3). The ICC between the two independent raters was very high for the DRS-R-98 –J Total: 0.99, and the DRS-R98 –J Severity: 0.99. ROC analyses were performed for DRS-R-98 –J scores, comparing delirium to non-delirium and dementia groups. Table 4 shows sensitivity and specificity for ROC analysis at various cutoff scores for the DRS-R-98 –J Total and Severity scales. Compared with the nondelirium group, the best cutoff score for the DRS-R-98 –J Total scale was 14.5, resulting in 98% sensitivity and 94% specificity, and for the DRS-R-98 –J Severity scale was 10.0, resulting in 98% sensitivity and 91% specificity. ROC analyses comparing delirium versus dementia, found that the best cutoff score for the DRS-R98 –J Total scale was 14.5, with 98% sensitivity and 75% specificity, and for the DRS-R-98 –J Severity scale was 11.5, resulting in 92% sensitivity and 75% specificity. Table 5 shows the SSLR of the DRS-R-98 –J Total scale for delirium. Scores of the DRS-R-98 –J Total scale between 12 and 15 would be of little assistance in delirium diagnosis. Psychosomatics 51:5, September-October 2010
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TABLE 4.
Sensitivity and Specificity of the DRS-R98 –J Total and Severity Scales, Based on Receiver Operating Characteristics (ROC) Analysis; Delirium vs. NonDelirium Groups, and Dementia Subgroup
Delirium vs. Non-Delirium Cutoff Score
Sensitivity (%)
Specificity (%)
10.5 13.5 14.5 15.5 16.5 20.5 21.5 5.5 8.5 10.0 11.5 13.5 17.5 20.5
100 98 98 94 88 69 65 100 98 98 92 83 60 44
82 91 94 94 94 97 100 70 85 91 94 94 97 100
Cutoff Score
Sensitivity (%)
Specificity (%)
10.5 12.5 14.5 15.5 18.5 20.5 21.5 5.3 8.0 10.0 11.5 13.5 17.5 20.5
100 98 98 94 82 69 65 100 98 98 92 83 60 44
50 63 75 75 75 88 100 13 50 63 75 75 88 100
Total Score
Severity Score
Delirium vs. Dementia
Total Score
Severity Score
TABLE 5.
Stratum-Specific Likelihood Ratios (SSLRs) of the DRS-R98 –J Total Scale for Delirium, Comparing Delirium and Non-Delirium Groups
Scores
Delirium
Non-Delirium
SSLR
95% Confidence Interval
0–11 12–15 16–20 ⱖ21
1 2 12 33
29 2 1 1
0.02 0.69 8.25 22.69
0.00–0.12 0.13–3.75 1.60–42.33 4.69–109.64
DISCUSSION This study indicates that the Japanese version of the DRSR-98 has high reliability and validity, and is a useful tool for assessing delirium among Japanese medically-ill popPsychosomatics 51:5, September-October 2010
ulations. DRS-R98 –J items have a high level of internal consistency, interrater reliability between two psychiatrists, concurrent validity with the MMSE and CGI-S-D delirium severity, and ability to detect change over time. The DRS-R-98 was developed primarily as an instrument for assessing the severity of delirium symptoms in serial ratings, in addition to use as a diagnostic tool, and this aim is supported by our results in Japanese patients. The DRS-R98 –J significantly differentiated between hospitalized patients with and without delirium, including those with dementia, using a total scale cutoff score of 14.5. This cutoff score is identical to the Colombian adaptation of the Spanish version (cutoff score is 14)11 and the Chinese version (cutoff scores is 15.5).13 However, the cutoff score of 14.5 on the DRS-R98 –J Total scale was lower than that in the original study (17.75),8 the Portuguese version (20.0),22 and the Korean study (21.5),12 possibly because of the greater severity of dementia in those studies that drive the cutoff score higher for differential diagnosis purposes.22 Patients with dementia in this study had only mild severity, as based on the mean MMSE of 20.3. Our delirium patients had somewhat lower mean DRS-R-98 scores than the original or Portuguese study.8,22 Our non-delirium group might also have lower psychiatric severity than other studies, given that we included four patients without Axis I psychiatric disorder and six patients with sleep disorder as a primary psychiatric illness; however, the DRS-R-98 score in our non-delirium group was close to the original DRS-R-98 report for schizophrenia (7.7), depression (7.0), and other groups (8.9). However, the mean total scale score in our non-delirium group, excluding the dementia patients, was 5.3, lower than in the original study. Cross-cultural differences in expression or rating of symptoms may also partially explain the groups’ scores being lower. Several clinical epidemiologists have recently criticized the use of the fixed cutoff thresholds, and have advocated multilevel or stratum-specific likelihood ratios (SSLRs).21 The SSLR approach has several advantages.21,23 It nicely incorporates the differences in pretest probabilities between populations and illustrates in clearer terms what we should do in the diagnostic processes of an individual or a group of individuals. A useful nomogram proposed by Fagan facilitates the translation of SSLRs into predicted probabilities.21,23,24 Furthermore, in the case of a continuous scale such as the DRS-R-98, SSLR retains more information than that given by a single cutoff and sensitivity and specificity approach. For example, given a patient whose pretest probability of delirium is 50% (clinhttp://psy.psychiatryonline.org
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Japanese Version of the DRS–98 ically uncertain), and he or she scores a total DRS-R98 –J score of 21, this provides an approximately 96% posttest probability. On the other hand, given another patient, whose pretest probability of delirium is 50% (clinically uncertain), and he or she scores a total DRS-R98 –J score of 11, this provides an approximately 1% posttest probability. This study showed that only 4.9% of the study participants had noninformative SSLRs (i.e., 4 out of the 81 patients had scores between 13 and 16), suggesting that this scale is a very useful clinical diagnostic tool. For example, given a patient whose pretest probability of delirium is 40% (clinically uncertain) and he or she scores a total DRS-R-98 –J score of 14 (around the cutoff score based on the ROC), this provides an approximately 32% posttest probability, which would not provide benefit in terms of changing the pre- and posttest diagnosis (i.e., differential diagnoses are difficult, and further observational clinical work should be necessary). It is important to acknowledge the methodological limitations of the study. First, over 70% of the underlying physical conditions of the study participants had cancer. Thus, the findings may not be applicable to all
medical and surgical patients. Several studies, however, show that the DRS-R-98 is proven to be valid in various medical and surgical conditions.8 –13 Second, the sample size of dementia was small (N⫽8) in this study. Furthermore, standardized psychiatric scales and structured clinical interviews were not used in the non-delirium patients. Further studies, with larger dementia sample sizes might be necessary to reassess the dementia and delirium groups. It would also be useful in assessing delirium superimposed on dementia. CONCLUSION The Japanese version of the DRS-R-98, the DRS-R-98 –J, appears to be a valid and reliable measure of delirium, not only assessing its severity but also its diagnosis. This scale can be used clinically to monitor the course of illness when administered serially. Its sufficient breadth of phenomenology offers research applications, as well. This work was presented as a poster at the Annual Meeting of the Academy of Psychosomatic Medicine, November 2005, Santa Ana Pueblo, NM.
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Kato et al. ical Literature, III: how to use an article about a diagnostic test, B: what are the results, and will they help me in caring for my patients? The Evidence-Based Medicine Working Group. JAMA 1994; 271:703–707 21. Furukawa TA, Goldberg DP, Rabe-Hesketh S, et al: Stratumspecific likelihood ratios of two versions of the General Health Questionnaire. Psychol Med 2001; 31:519 –529 22. Negreiros DP, Meleiro AM, Furlanetto LM, et al: Portuguese
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Version of the Delirium Rating Scale, Revised–98: reliability and validity. Int J Geriatr Psychiatry 2008; 23:472– 477 23. Furukawa TA, Andrews G, Goldberg DP: Stratum-specific likelihood ratios of the General Health Questionnaire in the community: help-seeking and physical comorbidity affect the test characteristics. Psychol Med 2002; 32:743–748 24. Fagan TJ: Nomogram for Bayes’ theorem (letter). N Engl J Med 1975; 293:257
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