The Digit Span Test is a very short test that evaluates a person's cognitive status. It is frequently used in hospitals and physicians' offices in order for a clinician to quickly evaluate whether a patient's cognitive abilities are normal.
The Digit Span Test initially was part of Wechsler's Intelligence Scale which was designed to measure a person's intelligence quotient (IQ).
How Is the Digit Span Test Administered?
The Digit Span Test consists of telling the person that you are going to give him a short test. The person is then told to listen carefully because you will say a series of numbers and ask him to repeat them back to you in the same order you say them.
The first series is three numbers, such as "3, 9, 2." Each number is said in a monotone voice, one second apart. The person repeats those numbers back to you.
The next step is to speak a series of four numbers, such as, "4, 7, 3, 1." Again, the individual repeats those back to you.
Continue in the same manner by increasing the series of numbers to five and asking the person to repeat the numbers back to you. Some test versions stop after a series of 5 numbers and other versions continue increasing the series of numbers by one each time and ask the person to repeat them back to you until the answers are incorrect.
Variations on the Digit Span Test
This test can be varied by asking the person to repeat the numbers backwards, that is, by starting with the last number you said and going backwards to the first number you said. This is called the Digit Span Test Backwards.
The Digit Span Test can also be given visually by displaying a series of numbers and then asking the person taking the test to verbally state the numbers and then to write them down in the correct order. This is referred to as the Visual Digit Span Test and can be administered either forward or backward.
What Does the Digit Span Test Measure?
What Score Indicates Impaired Cognition?
Sources vary about the cutoff for a normal score. One suggests that if a person is unable to repeat seven numbers forwards and five numbers backwards, dementia is likely present. Another states that the inability to repeat five numbers forwards indicates delirium. There appears to be a range of scores, but the inability to accurately repeat less than five numbers seems indicative of a concern.
Is the Digit Span Test Effective in Identifying Dementia?
In an article published in the International Journal of Alzheimer's Disease, the Digit Span Test demonstrated the ability to successfully identify someone with cognitive impairment and the researchers concluded it should be part of a battery of tests used to detect mild cognitive impairment.
A second study conducted in Thailand found that the Digit Span Test was effective in identifying mild cognitive decline, while the verbal fluency test did not demonstrate that ability.
Detecting mild cognitive decline is important for early detection and treatment of dementia.
Does the Digit Span Test Also Screen for Delirium?
The test can be used as a screen for both delirium and dementia. One study found that it was also able to also identify the combination of delirium and dementia, a condition called delirium superimposed on dementia.
What Are the Pros and Cons of the Digit Span Test?
This test is free, and it requires less than five minutes to administer. The administrator does not require extensive training, and it appears to be effective in identifying cognitive problems in multiple cultures and languages.
The test is a screening tool and it may be difficult to distinguish between delirium and dementia in patients where their history is not known.
Is the Digit Span Test Recommended?
The Digit Span Test should be combined with other tests to develop an accurate picture of the person's cognitive abilities, but when used as a quick screening, it may assist in identifying cognitive concerns.
International Journal of Alzheimer's Disease Volume 2012. Clinical Study: Lack of Correlation of WAIS Digit Span with Clox 1 and the Dementia Rating Scale in MCI. http://www.hindawi.com/journals/ijad/2012/829743/
International Psychogeriatrics. 2011 Dec;23(10):1569-74. The use of the Digit Span Test in screening for cognitive impairment in acute medical inpatients. http://www.ncbi.nlm.nih.gov/pubmed/21729426
Journal of the Medical Association of Thailand. 2010 Feb;93(2):224-30. Digit span and verbal fluency tests in patients with mild cognitive impairment and normal subjects in Thai-community. http://www.ncbi.nlm.nih.gov/pubmed/20302005
The Mereck Manual for Healthcare Providers. Delirium. Accessed June 25, 2013. http://www.merckmanuals.com/professional/neurologic_disorders/delirium_and_dementia/delirium.html
Society of Hospital Medicine. Clinical Toolbox for Geriatric Care. Digit Span Test. http://www.hospitalmedicine.org/geriresource/toolbox/pdfs/digit_span_test.pdf