Double Letter Cancellation Test (DLCT)

Purpose

The Double Letter Cancellation Test (DLCT) is used to evaluate the presence and severity of visual scanningDuring this intervention the person with USN is encouraged to conduct voluntary eye movements toward the neglected visual field (usually the left side) by performing a task in that hemispace. The treatment often includes a visual target that the patient uses as an anchor to direct voluntary gaze control while scanning.
deficits, and is used to evaluate unilateral spatial neglect (USN) in the near extrapersonal space (Diller, Ben-Yishay, Gertsman, Goodkin, Gordon, & Weinberg, 1974).

In-Depth Review

Purpose of the measure

The Double Letter Cancellation Test (DLCT) is used to evaluate the presence and severity of visual scanningDuring this intervention the person with USN is encouraged to conduct voluntary eye movements toward the neglected visual field (usually the left side) by performing a task in that hemispace. The treatment often includes a visual target that the patient uses as an anchor to direct voluntary gaze control while scanning.
deficits, and is used to evaluate unilateral spatial neglect (USN) in the near extrapersonal space (Diller, Ben-Yishay, Gertsman, Goodkin, Gordon, & Weinberg, 1974).

Available versions

The DLCT was published by Diller et al. in 1974.

Features of the measure

Items:
There are no actual items for the DLCT.

The patient is asked to look at an 8.5″x11″ sheet of paper containing 6 lines with 52 letters per line. Together, the stimuli letters C and E are presented 105 times. The patient is instructed to put a mark through all the letters C and E. The time taken to complete the test is recorded.

This test may be more challenging than cancellation of shapes or colours, since it requires the discrimination of 2 letters (C and E) from the rows of letters. The letters are arranged in structured rows and thus require less organizational skills than when the forms are randomly scattered on the page. This enables the therapist to examine more closely the issue of attention without the confounding factor of visual organization.

To begin the DLCT, the therapist places the test sheet at the patient’s midline and secures it with tape, and points to the trial line, asking the patient to mark the Cs and Es. If the patient is unable to perform the trial, further instruction is given. If the trial is correctly performed, the therapist will then proceed to give instructions as follows: “Look at the letters on this page. Put one line through each C and E. Ready, begin here”. The therapist points to the first letter in the first row and begins timing the patient.

Scoring:
The score is calculated by subtracting the number of omissions (Cs and Es that were not crossed out) from the possible perfect score of 105. Higher scores indicate better performance. The timing and total number of errors should be noted. According to Diller et al. (1974) 13 control subjects had a median error of 1 with a performance time of 100 seconds. Errors on the right with those on the left side of the page should be compared. Randomly scattered errors indicate poor sustained attention. Errors concentrated on one half of the page (either left or right) indicate USN. Commissions are rarely seen and are therefore not included in the analyses.

The patient’s general approach to the task should be observed (i.e. does the patient work from left to right or move randomly over the page; is their response time slowed; does the patient selectively choose the correct response or frequently mark non-target letters).

Normative data has been published by sex and age, based on the results from 241 patients with lesions of the right hemisphere (Gordon, Ruckdeschel-Hibbard, Egelko, Diller, Simmens, & Langer, 1984).

Time:
Less than 5 minutes.

Training:
None typically reported.

Subscales:
None.

Equipment:

• 11x 8.5-inch page of paper containing 6 lines with 52 letters per line and the stimulus letters C and E presented 105 times.
• Pencil
• Stopwatch

Alternative Forms of the DLCT

• Number version of the DLCT (Wade, Wood, & Hewer, 1988).p>A test similar to the DLCT has been created using numbers instead of letters. The patient is asked to cancel all the 1s and 4s from the rows of numbers. Normative data for this form of the DLCT was gathered from 51 elderly individuals (Wade et al., 1988).
• Letter cancellation subtest of the Behavioural Inattention Test (Wilson, Cockburn, & Halligan, 1987).
  The patient is presented with a sheet of paper with five lines of letters (34 per line). The patient is instructed to put a mark through all the letters E and R. The maximum score is 40 (20 left, 20 right).

Client suitability

Can be used with:

Patients with strokeAlso called a “brain attack” and happens when brain cells die because of inadequate blood flow. 20% of cases are a hemorrhage in the brain caused by a rupture or leakage from a blood vessel. 80% of cases are also know as a “schemic stroke”, or the formation of a blood clot in a vessel supplying blood to the brain..

• Patients must be able to hold a pencil to complete the test (the presence of apraxia may impair this ability).
• Patients must be able to recognize letters of the alphabet to complete the test.

Should not be used with:

• The DLCT requires language skills sufficient to identify letters. Therefore the DLCT may not be appropriate for patients with receptive aphasiaAphasia is an acquired disorder caused by an injury to the brain and affects a person’s ability to communicate. It is most often the result of stroke or head injury.
  An individual with aphasia may experience difficulty expressing themselves when speaking, difficulty understanding the speech of others, and difficulty reading and writing. Sadly, aphasia can mask a person’s intelligence and ability to communicate feelings, thoughts and emotions. (The Aphasia Institute, Canada).
• The DLCT may not be appropriate for patients with poor vision as the letters may appear too small.
• The DLCT cannot be used to differentiate between sensory neglect and motor neglect because it requires both visual search and manual exploration (Ladavas, 1994).
• The DLCT cannot be completed by proxy.

In what languages is the measure available?

The DLCT has been used with English and French-speak patients.

A Hebrew version of the DLCT has been used in some studies as part of the Behavioral Inattention Test (e.g. Friedman & Nachman-Katz, 2004).

Summary

What does the tool measure?	Unilateral Spatial Neglect (USN) in the near extrapersonal space.
What types of clients can the tool be used for?	Patients with strokeAlso called a “brain attack” and happens when brain cells die because of inadequate blood flow. 20% of cases are a hemorrhage in the brain caused by a rupture or leakage from a blood vessel. 80% of cases are also know as a “schemic stroke”, or the formation of a blood clot in a vessel supplying blood to the brain..
Is this a screeningTesting for disease in people without symptoms. or assessment tool?	ScreeningTesting for disease in people without symptoms. .
Time to administer	Less than 5 minutes.
Versions	None.
Other Languages	The DLCT has been used with English and French-speak patients. A Hebrew version of the DLCT has been used in some studies as part of the Behavioural Inattention Test.
Measurement Properties
ReliabilityReliability can be defined in a variety of ways. It is generally understood to be the extent to which a measure is stable or consistent and produces similar results when administered repeatedly. A more technical definition of reliability is that it is the proportion of “true” variation in scores derived from a particular measure. The total variation in any given score may be thought of as consisting of true variation (the variation of interest) and error variation (which includes random error as well as systematic error). True variation is that variation which actually reflects differences in the construct under study, e.g., the actual severity of neurological impairment. Random error refers to “noise” in the scores due to chance factors, e.g., a loud noise distracts a patient thus affecting his performance, which, in turn, affects the score. Systematic error refers to bias that influences scores in a specific direction in a fairly consistent way, e.g., one neurologist in a group tends to rate all patients as being more disabled than do other neurologists in the group. There are many variations on the measurement of reliability including alternate-forms, internal consistency , inter-rater agreement , intra-rater agreement , and test-retest .	Internal consistencyA method of measuring reliability . Internal consistency reflects the extent to which items of a test measure various aspects of the same characteristic and nothing else. Internal consistency coefficients can take on values from 0 to 1. Higher values represent higher levels of internal consistency.: No studies have examined the internal consistencyA method of measuring reliability . Internal consistency reflects the extent to which items of a test measure various aspects of the same characteristic and nothing else. Internal consistency coefficients can take on values from 0 to 1. Higher values represent higher levels of internal consistency. of the DLCT. Test-retest: One study has examined the test-retest reliabilityA way of estimating the reliability of a scale in which individuals are administered the same scale on two different occasions and then the two scores are assessed for consistency. This method of evaluating reliability is appropriate only if the phenomenon that the scale measures is known to be stable over the interval between assessments. If the phenomenon being measured fluctuates substantially over time, then the test-retest paradigm may significantly underestimate reliability. In using test-retest reliability, the investigator needs to take into account the possibility of practice effects, which can artificially inflate the estimate of reliability (National Multiple Sclerosis Society). of the DLCT and reported adequate test-retest.
ValidityThe degree to which an assessment measures what it is supposed to measure.	Construct: Adequate correlationThe extent to which two or more variables are associated with one another. A correlation can be positive (as one variable increases, the other also increases – for example height and weight typically represent a positive correlation) or negative (as one variable increases, the other decreases – for example as the cost of gasoline goes higher, the number of miles driven decreases. There are a wide variety of methods for measuring correlation including: intraclass correlation coefficients (ICC), the Pearson product-moment correlation coefficient, and the Spearman rank-order correlation. with mean CT-scan damage.
Does the tool detect change in patients?	Not applicable.
Acceptability	The DLCT should be used as a screeningTesting for disease in people without symptoms. tool rather than for clinical diagnosis of USN. Apraxia must be ruled out as this may affect the validityThe degree to which an assessment measures what it is supposed to measure. of test results. – This test cannot be completed by proxy. The DLCT is known to be a more taxing measure of USN than the Single Letter Cancellation Test. Patients must be able to hold a pencil. The DLCT requires language skills sufficient to identify letters, and therefore may not be suitable for patients with receptive aphasiaAphasia is an acquired disorder caused by an injury to the brain and affects a person’s ability to communicate. It is most often the result of stroke or head injury. An individual with aphasia may experience difficulty expressing themselves when speaking, difficulty understanding the speech of others, and difficulty reading and writing. Sadly, aphasia can mask a person’s intelligence and ability to communicate feelings, thoughts and emotions. (The Aphasia Institute, Canada). Patients with poor vision may not be able to complete the DLCT as the letters may appear too small. The DLCT cannot be used to differentiate between sensory neglect and motor neglect.
Feasibility	The DLCT requires no specialized training to administer and only minimal equipment is required (a pencil, a stopwatch, and the test paper). The test is simple to score and interpret. No suggested cutoff score for the presence of USN is provided for the DLCT, however normative data has been published (see Gordon, Ruckdeschel-Hibbard, Egelko, Diller, Simmens, & Langer, 1984). The test is placed at the patient’s midline and is secured with tape. The time it takes for the patient to complete the test is recorded.
How to obtain the tool?	Please click here to see a copy of the DLCT.

Psychometric Properties

Overview

In general, cancellation tests are believed to have greater test-retest reliabilityA way of estimating the reliability of a scale in which individuals are administered the same scale on two different occasions and then the two scores are assessed for consistency. This method of evaluating reliability is appropriate only if the phenomenon that the scale measures is known to be stable over the interval between assessments. If the phenomenon being measured fluctuates substantially over time, then the test-retest paradigm may significantly underestimate reliability. In using test-retest reliability, the investigator needs to take into account the possibility of practice effects, which can artificially inflate the estimate of reliability (National Multiple Sclerosis Society).
than line bisection tests and are often more sensitive for detecting USN than line bisection tests (Marsh & Kersel, 1993; Azouvi et al., 2002). The DLCT has been reported to have adequate psychometric properties, including some evidence of reliabilityReliability can be defined in a variety of ways. It is generally understood to be the extent to which a measure is stable or consistent and produces similar results when administered repeatedly. A more technical definition of reliability is that it is the proportion of "true" variation in scores derived from a particular measure. The total variation in any given score may be thought of as consisting of true variation (the variation of interest) and error variation (which includes random error as well as systematic error). True variation is that variation which actually reflects differences in the construct under study, e.g., the actual severity of neurological impairment. Random error refers to "noise" in the scores due to chance factors, e.g., a loud noise distracts a patient thus affecting his performance, which, in turn, affects the score. Systematic error refers to bias that influences scores in a specific direction in a fairly consistent way, e.g., one neurologist in a group tends to rate all patients as being more disabled than do other neurologists in the group. There are many variations on the measurement of reliability including alternate-forms, internal consistency , inter-rater agreement , intra-rater agreement , and test-retest .
and validityThe degree to which an assessment measures what it is supposed to measure.
, in identifying USN in the near extrapersonal space (Menon & Korner-Bitensky, 2004). For the purposes of this review, we conducted a literature search to identify all relevant publications on the psychometric properties of the DLCT.

Reliability

Internal consistencyA method of measuring reliability . Internal consistency reflects the extent to which items of a test measure various aspects of the same characteristic and nothing else. Internal consistency coefficients can take on values from 0 to 1. Higher values represent higher levels of internal consistency.:
No evidence.

Test-retest.:
Gordon et al. (1984) examined the test-retest reliabilityA way of estimating the reliability of a scale in which individuals are administered the same scale on two different occasions and then the two scores are assessed for consistency. This method of evaluating reliability is appropriate only if the phenomenon that the scale measures is known to be stable over the interval between assessments. If the phenomenon being measured fluctuates substantially over time, then the test-retest paradigm may significantly underestimate reliability. In using test-retest reliability, the investigator needs to take into account the possibility of practice effects, which can artificially inflate the estimate of reliability (National Multiple Sclerosis Society).
of the DLCT using a group of 31 subjects and found adequate test-retest (r = 0.62).

Validity

Construct:
Egelko et al. (1988) found that the DLCT correlated adequately with mean CT-scan damage (r = -0.35).

Note: This correlationThe extent to which two or more variables are associated with one another. A correlation can be positive (as one variable increases, the other also increases – for example height and weight typically represent a positive correlation) or negative (as one variable increases, the other decreases – for example as the cost of gasoline goes higher, the number of miles driven decreases. There are a wide variety of methods for measuring correlation including: intraclass correlation coefficients (ICC), the Pearson product-moment correlation coefficient, and the Spearman rank-order correlation.
is negative because a high score on the DLCT indicates better performance, whereas a high CT-scan score indicates more brain damage.

Criterion:
No evidence.

Responsiveness

No evidence.

References

• Azouvi, P., Samuel, C., Louis-Dreyfus, A., et al. (2002). Sensitivity of clinical and behavioural tests of spatial neglect after right hemisphere stroke. J Neurol Neurosurg Psychiatry, 73, 160 -166.
• Diller, L., Ben-Yishay, Y., Gerstman, L. J., Goodin, R., Gordon, W., Weinberg, J. (1974). Studies in scanning behavior in hemiplegia. Rehabilitation Monograph No. 50, Studies in cognition and rehabilitation in hemiplegia. New York: New York University Medical Center, Institute of Rehabilitation Medicine.
• Egelko, S., Gordon, W. A., Hibbard, M. R., Diller, L., Lieberman, A., Holliday, R., Ragnarsson, K., Shaver, M. S., Orazem, J. (1988). Relationship among CT scans, neurological exam, and neuropsychological test performance in right-brain-damaged stroke patients. J Clin Exp Neuropsychol, 10, 539-564.
• Friedmann, N., Nachman-Katz, I. (2004). Developmental neglect dyslexia in a hebrew-reading child. Cortex, 40(2), 301-313.
• Gordon, W. A., Ruckdeschel-Hibbard, M., Egelko, S., Diller, L., Simmens, S., Langer, K., Sano, M., Orazem, J., Weinberg, J. (1984). Single Letter Cancellation Test in Evaluation of the Deficits Associated with Right Brain Damage: Normative Data on the Institute of Rehabilitation Medicine Test Battery. pp1-7, New York: New York University Medical Center.
• Ladavas, E. (1994). The role of visual attention in neglect: A dissociation between perceptual and directional motor neglect. Neuropsychological Rehabilitation, 4, 155-159.
• Marsh, N. V., Kersel, D. A. (1993). Screening tests for visual neglect following stroke. Neuropsychological Rehabilitation, 3, 245-257.
• Menon, A., Korner-Bitensky, N. (2004). Evaluating unilateral spatial neglect post stroke: Working your way through the maze of assessment choices. Topics in Stroke Rehabilitation, 11(3), 41-66.
• Wade, D. T., Wood, V. A., Hewer, R. L. (1988). Recovery of cognitive function soon after stroke: A study of visual neglect, attention span and verbal recall. Journal of Neurology, Neurosurgery ,and Psychiatry, 51, 10-13.
• Wilson, B., Cockburn, J., Halligan, P. (1987). Development of a behavioural test of visuospatial neglect. Archives of Physical Medicine and Rehabilitation, 68, 98-102.

See the measure

How to obtain the DLCT?

The DLCT can be purchased as part of the Behavioral Inattention Test from Harcourt Assessment by clicking on the following link: http://www.harcourt-uk.com/product.aspx?skey=2906
Click here to view a copy of the DLCT as it appears in the Behavioral Inattention Test.