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The use of the Digit Span Test in screening for cognitive impairment in acute medical inpatients

Published online by Cambridge University Press:  17 May 2011

Jess L. M. Leung ,
Gary T. H. Lee ,
Y. H. Lam ,
Ray C. C. Chan  and
Jimmy Y. M. Wu
Jess L. M. Leung*
Affiliation:
Department of Psychiatry, United Christian Hospital, Kwun Tong, Kowloon, Hong Kong
Gary T. H. Lee
Affiliation:
Department of Psychiatry, United Christian Hospital, Kwun Tong, Kowloon, Hong Kong
Y. H. Lam
Affiliation:
Department of Medicine and Geriatrics, United Christian Hospital, Kwun Tong, Kowloon, Hong Kong
Ray C. C. Chan
Affiliation:
Department of Medicine and Geriatrics, United Christian Hospital, Kwun Tong, Kowloon, Hong Kong
Jimmy Y. M. Wu
Affiliation:
Department of Geriatrics and Rehabilitation, Haven of Hope Hospital, Tseung Kwan O, New Territories, Hong Kong
*
Correspondence should be addressed to: Dr. Jess L.M. Leung, Department of Psychiatry, United Christian Hospital, Kwun Tong, Kowloon, Hong Kong. Phone: +852 97713732; Fax: +852 35135505. Email: leunglmjess@gmail.com.
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Abstract

Background: There is no valid instrument currently in use at acute-care hospitals in Hong Kong to aid the detection of cognitive impairment. The objectives of this study were to (1) validate the Digit Span Test (DST) in the identification and differentiation of dementia and delirium; and (2) determine the prevalence of major cognitive impairment in elderly people in an acute medical unit.

Methods:During the study period from January to February 2010, 144 patients aged 75 years or more who had had unplanned medical admissions were assessed by nurses, using the Digit Span Forwards (DSF) and the Digit Span Backwards (DSB) tests. The DST scores were compared with the psychiatrists’ DSM-IV-based diagnoses. Receiver Operating Characteristics curve (ROC) was used in conjunction with sensitivity and specificity measures to assess the performance of DST.

Results: The prevalence rates of dementia alone, delirium alone and delirium superimposed on dementia were 21.5%, 9% and 9% respectively. The prior case-note documentation rate was 13.2% for dementia and 2.8% for delirium. Regarding the detection of major cognitive impairment, the ROC curve of DSB showed a sensitivity of 0.77 and specificity of 0.78 at the optimal cutoff of <3. A significant association between scores on the DST and the Cantonese version of the Mini-Mental State Examination (CMMSE) was found in this study (p < 0.05 for DSF, p = 0.00 for DSB).

Conclusions: Dementia and delirium were prevalent, yet under-recognized, in acute medical geriatric inpatients. The DSB is an effective tool in identifying patients with major cognitive impairment.

Keywords

dementiadeliriumgeriatricattention deficit
Type
Research Article
Information
International Psychogeriatrics , Volume 23 , Issue 10 , December 2011 , pp. 1569 - 1574
Copyright
Copyright © International Psychogeriatric Association 2011

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