Sunnybrook Neglect Assessment Procedure (SNAP)

Purpose

The Sunnybrook Neglect Assessment Procedure (SNAP) is a test battery to screen for neglect in patients with acute 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. (Black et al., 2016).

In-Depth Review

Purpose of the measure

The Sunnybrook Neglect Assessment Procedure (SNAP) is a test battery for bedside screeningTesting for disease in people without symptoms.
of neglect. It is designed to assess neglect in patients with acute 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. and to monitor recovery of neglect at later stages of 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. recovery.

Available versions

There is one version of the SNAP.

Features of the measure

Items:
The SNAP is comprised of five paper-and-pencil items that are familiar measures of neglect. The items are administered to the patient in the following order:

1. Spontaneous drawing of clock and daisy
2. Line cancellation task
3. Line bisection task
4. Copying of clock and daisy
5. Shape cancellation

Description of tasks:
A1. Drawing task
The patient is asked to draw a clock face and a daisy on a blank piece of paper.

B. Line Cancellation Task
The patient is instructed to cross out all lines on a page.

C. Line Bisection Task
The patient is instructed to draw a mark on a line in order to bisect the line in half. This task is completed using 15cm and 20cm lines.

A2. Copying Tasks
The patient is asked to copy a picture of a clock and a daisy.
Note: The assessor does not identify that the pictures are a clock and a daisy.

D. Shape Cancellation Task
The patient is required to circle all the targets on a page.
Note: This is a timed task. The patient is given a different color pencil after every tenth target is circled, to determine the search pattern.

Scoring and score interpretation:
The scoring of the different SNAP subtests is based on omissions made on the contralateral side of the brain lesion. Left-side omissions are scored in patients in right hemisphere 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. and right-side omissions are scored in left hemisphere 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..

A. Copying and drawing tasks
Drawings with a significant omission of details on the contralateral side are scored as having neglect.

B. Line Cancellation
Each omitted line on the contralateral side of the page is scored as neglect.

C. Line Bisection
The score for this task is based on the mean percent deviation of the patient’s mark from the true midpoint. Percent deviation and average deviation is calculated for the four lines of the task, according to the formula stipulated in the SNAP manual.

D.Shape cancellation task
All targets omitted on the contralateral side of the page are counted.

Total score interpretation:

Scores are calculated using the SNAP scoring manual. The patient is awarded a score for each subtest, resulting in a total score out of 100.

Leibovitch et al. (2012) recommended classifying severity of neglect according to performance on the SNAP as follows:

SNAP Score	Classification of Performance
0-5	Normal Performance
6-40	Mild Neglect
41-100	Severe Neglect

Please see the SNAP Administration and Scoring Manual for more details on scoring (Black et al., 2016).

What to consider before beginning:
SNAP test items should always be placed in the individual’s midline.

Time:
Time taken to administer the assessment has not been specified. Time will vary according to the patient’s attention and severity of neglect.

Training:
Training requirements have not been specified.

Subscales:
None.

Equipment:

• SNAP assessment package
• Two blank sheets of paper
• Coloured pens/pencils
• Stopwatch

Alternative forms of the SNAP

The original version of the Sunnybrook Neglect Assessment contained additional drawing tasks, a paragraph reading task, a writing task and additional visual search tasks. The four items that comprise the SNAP were deemed to be complementary and not redundant, so the additional items were eliminated (Leibovitch et al., 2012).

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..

Should not be used with:

• Not specified.

In what languages is the measure available?

English.

Summary

What does the tool measure?	Hemispatial neglect
What types of clients can the tool be used for?	Patients in the acute phase of 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. recovery.
What ICF domain is measured?	Impairment.
Is this a screeningTesting for disease in people without symptoms. or assessment tool?	ScreeningTesting for disease in people without symptoms. .
Time to administer	Not specified.
Versions	There is one version of the SNAP.
Languages	English.
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.: One study reported moderate to excellent correlations between subtests and the total score. Test-retest: No studies have reported on 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). among 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.. Intra-rater/inter-rater: One study reported adequate to excellent correlations for subtests and the total score.
ValidityThe degree to which an assessment measures what it is supposed to measure.	Criterion: Concurrent: No studies have reported on concurrent validityTo validate a new measure, the results of the measure are compared to the results of the gold standard obtained at approximately the same point in time (concurrently), so they both reflect the same construct. This approach is useful in situations when a new or untested tool is potentially more efficient, easier to administer, more practical, or safer than another more established method and is being proposed as an alternative instrument. See also “gold standard.” of the SNAP among 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.. Predictive: One study reported that the SNAP significantly predicted neglect (present/absent) on the visual search board (VSB) visual search task. Construct: – One study reported a moderate 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. among SNAP subtests. – Two studies have conducted factor analysis and found that all subtests loaded on one factor that accounted for 69-72% of the variance. Convergent/Discriminant: – One study reported adequate correlations with the visual search board (VSB) visual search task. – One study reported a significant 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. between neglect measured by the SNAP and parietal damage. – One study reported an excellent 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. between the SNAP and a measure of generalized attentional capacity (digit span forward minus digit span backward). Known groups: One study reported significant differences in performance on the SNAP according to side of lesion.
Floor/Ceiling Effects	No studies have reported on floor/ceiling effects among 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..
SensitivitySensitivity refers to the probability that a diagnostic technique will detect a particular disease or condition when it does indeed exist in a patient (National Multiple Sclerosis Society). See also “Specificity.” / SpecificitySpecificity refers to the probability that a diagnostic technique will indicate a negative test result when the condition is absent (true negative).	– One study reported 68% sensitivitySensitivity refers to the probability that a diagnostic technique will detect a particular disease or condition when it does indeed exist in a patient (National Multiple Sclerosis Society). See also “Specificity.” and 76% specificitySpecificity refers to the probability that a diagnostic technique will indicate a negative test result when the condition is absent (true negative). . – Two studies reported that the shape cancellation task was the most sensitive subtest; a third study reported that the line bisection task was the most sensitive subtest. – One study reported that the drawing/copying subtests showed highest specificitySpecificity refers to the probability that a diagnostic technique will indicate a negative test result when the condition is absent (true negative). .
Does the tool detect change in patients?	The tool does not detect or measure change but it can be used to monitor change in neglect over time.
Acceptability	The SNAP is simple to administer and can be used at the individual’s bedside.
Feasibility	The SNAP is portable, quick to administer and requires minimal equipment.
How to obtain the tool?	The SNAP administration and scoring manual and test booklet can be accessed here

Psychometric Properties

Overview

A literature search was conducted to identify all relevant publications on the psychometric properties of the Sunnybrook Neglect Assessment Procedure (SNAP) for use 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.. Five articles were reviewed.

Floor/Ceiling Effects

Leibovitch et al (2012) examined psychometric properties of the SNAP in a sample of 224 patients with acute 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. and 100 elderly individuals. Results from the population of elderly individuals without 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. showed no omissions of details on the drawing/copying subtests and no omissions on the line cancellation subtest.

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.:
Leibovitch et al (2012) examined 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 SNAP in a sample of 224 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 with acute 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., using Cronbach’s coefficient alpha. All subtests showed an excellent 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 the total neglect score (alpha = 0.84, p < 0.001) and correlations between subtests were moderate (alpha < 0.07, p < 0.0005). This indicates that subtests are measuring the same construct but are not redundant.

Test-retest:
There are no studies of 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 SNAP among 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..

Intra-rater/inter-rater:
Leibovitch et al (2012) examined intra-rater and inter-rater reliabilityA method of measuring reliability . Inter-rater reliability determines the extent to which two or more raters obtain the same result when using the same instrument to measure a concept.
in a sample of 12 patients with acute 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. and 12 elderly individuals. Intra-rater reliabilityThis is a type of reliability assessment in which the same assessment is completed by the same rater on two or more occasions. These different ratings are then compared, generally by means of correlation. Since the same individual is completing both assessments, the rater's subsequent ratings are contaminated by knowledge of earlier ratings.
was measured with 1 rater and inter-rater reliabilityA method of measuring reliability . Inter-rater reliability determines the extent to which two or more raters obtain the same result when using the same instrument to measure a concept.
was measured between 2 raters. 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 .
was measured using Kappa statistics for drawing/copying tasks and interclass 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.
coefficients for other scores. The authors reported adequate to excellent correlations for subtests and the total score (r = 0.73-0.99, p < 0.001); specific statistics were not provided.

Validity

Content:
Development of the SNAP is not reported.

Criterion:
Concurrent:
No studies have reported on concurrent validityTo validate a new measure, the results of the measure are compared to the results of the gold standard obtained at approximately the same point in time (concurrently), so they both reflect the same construct. This approach is useful in situations when a new or untested tool is potentially more efficient, easier to administer, more practical, or safer than another more established method and is being proposed as an alternative instrument. See also “gold standard.”
of the SNAP among 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..

Predictive:
Leibovitch et al (2012) examined predictive validityA form of criterion validity that examines a measure’s ability to predict some subsequent event. Example: can the Berg Balance Scale predict falls over the following 6 weeks? The criterion standard in this example would be whether the patient fell over the next 6 weeks.
of the SNAP by comparison with the visual search board (VSB) visual search task (Kimura, 1986) in a sample of 224 patients with acute 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., using logistic regression. Comparison of test results showed that the SNAP significantly predicted neglect (present/absent) on the VSB.

Construct:
Black et al. (1995) examined construct validityReflects the ability of an instrument to measure an abstract concept, or construct. For some attributes, no gold standard exists. In the absence of a gold standard , construct validation occurs, where theories about the attribute of interest are formed, and then the extent to which the measure under investigation provides results that are consistent with these theories are assessed.
of the SNAP in a sample of 294 patients with acute 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.. SNAP subtest scores correlated significantly (r = 0.4-0.6, p = 0,0001). Initial factor analysis showed that all four tests contributed to a single factor which accounted for 72% of the information contained in the four subtests.

Leibovitch et al. (2012) examined construct validityReflects the ability of an instrument to measure an abstract concept, or construct. For some attributes, no gold standard exists. In the absence of a gold standard , construct validation occurs, where theories about the attribute of interest are formed, and then the extent to which the measure under investigation provides results that are consistent with these theories are assessed.
of the SNAP in a sample of 224 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 with acute 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., using factor analysis of subtest scores. Results revealed all subtests loaded equally on one factor that accounted for 69.4% of the total variance (eigenvalue = 2.8). Further factor analysis according to side of brain injury similarly showed that, among patients with right hemisphere damage, all four subtests loaded equally on one factor that accounted for 69% of the total variance. Results of patients with left hemisphere damage revealed two factors accounting for 62% of the total variance: the first factor comprised three subtests (drawing/copying, line cancellation and shape cancellation) and accounted for 37% of total variance; the second factor (line bisection) accounted for 25% of the total variance.

Convergent/Discriminant:
Leibovitch et al. (2012) examined convergent validityA type of validity that is determined by hypothesizing and examining the overlap between two or more tests that presumably measure the same construct. In other words, convergent validity is used to evaluate the degree to which two or more measures that theoretically should be related to each other are, in fact, observed to be related to each other.
of the SNAP by comparison with the visual search board (VSB) visual search task (Kimura, 1986) in a sample of 224 patients with acute 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., using Receiver Operating Characteristic analysis. Results showed adequate validityThe degree to which an assessment measures what it is supposed to measure.
(area under curve = 0.78).

Leibovitch et al. (1998) examined convergent validityA type of validity that is determined by hypothesizing and examining the overlap between two or more tests that presumably measure the same construct. In other words, convergent validity is used to evaluate the degree to which two or more measures that theoretically should be related to each other are, in fact, observed to be related to each other.
of the SNAP by comparison with location and severity of brain damage on CT and SPECT scans in a sample of 120 patients with acute/subacute 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., using regression analysis. Results showed that damage to the parietal and anterior cingulate cortex was a significant predictor of neglect using CT data (p<0.05), whereas regional blood flow in the parietal cortex was the best predictor of neglect using SPECT data (p<0.05).

Eskes et al. (2003) examined convergent validityA type of validity that is determined by hypothesizing and examining the overlap between two or more tests that presumably measure the same construct. In other words, convergent validity is used to evaluate the degree to which two or more measures that theoretically should be related to each other are, in fact, observed to be related to each other.
of the SNAP by comparison with a measure of generalized attentional capacity (digit span forward minus digit span backward) in a sample of 9 patients with acute to chronic 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., using Spearman 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.
coefficient. Results showed an excellent 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.
between measures (r=0.85, p<0.02).

Known groups:
Black et al. (1995) administered the SNAP to 294 patients with acute 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.. Comparison of incidence of neglect between patients with right hemisphere damage vs. patients with left hemisphere damage was 54% vs. 31% (respectively). Performance on SNAP subtests differed significantly between groups: Shape cancellation: 74% vs. 54% (respectively); Line bisection: 61% vs. 35 % (respectively); Line cancellation: 26% vs. 7% (respectively); and Drawing: 25% vs. 3% (respectively).

Responsiveness

SensitivitySensitivity refers to the probability that a diagnostic technique will detect a particular disease or condition when it does indeed exist in a patient (National Multiple Sclerosis Society). See also “Specificity.”
/specificity:
Black et al. (1990) used a modified version of the SNAP in a sample of 41 patients with acute 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. (n=21 with right hemisphere damage). The tool comprised the standard SNAP subtests as well as two additional tasks (designs cancellation, visual search). Results showed that the line bisection task was the most sensitive subtest, with neglect observed in 76% and 30% of individuals with right and left hemisphere damage respectively. While the line bisection subtest was most likely to detect mild impairment, the line drawing and line cancellation subtests indicated more severe impairment.

Black et al (1995) administered the SNAP to 294 patients with acute 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.. Comparison of incidence of neglect between patients with right hemisphere damage vs. left hemisphere damage was 54% vs. 31% (respectively). Results indicate that the shape cancellation subtest was the most sensitive subtest, with neglect observed in 74% and 54% of individuals with right and left hemisphere damage respectively. The line bisection subtest revealed neglect in 61% and 35% of individuals with right and left hemisphere damage respectively.

Leibovitch et al. (2012) evaluated sensitivitySensitivity refers to the probability that a diagnostic technique will detect a particular disease or condition when it does indeed exist in a patient (National Multiple Sclerosis Society). See also “Specificity.”
and specificitySpecificity refers to the probability that a diagnostic technique will indicate a negative test result when the condition is absent (true negative).
of the SNAP in a sample of 224 patients with acute 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., using the visual search board (VSB) visual search task (Kimura, 1986) to confirm neglect. Overall, the SNAP showed 68% sensitivitySensitivity refers to the probability that a diagnostic technique will detect a particular disease or condition when it does indeed exist in a patient (National Multiple Sclerosis Society). See also “Specificity.”
and 76% specificitySpecificity refers to the probability that a diagnostic technique will indicate a negative test result when the condition is absent (true negative).
. The shape cancellation task showed highest sensitivitySensitivity refers to the probability that a diagnostic technique will detect a particular disease or condition when it does indeed exist in a patient (National Multiple Sclerosis Society). See also “Specificity.”
(70% sensitivitySensitivity refers to the probability that a diagnostic technique will detect a particular disease or condition when it does indeed exist in a patient (National Multiple Sclerosis Society). See also “Specificity.”
); the drawing/copying tasks showed highest specificitySpecificity refers to the probability that a diagnostic technique will indicate a negative test result when the condition is absent (true negative).
(99% specificitySpecificity refers to the probability that a diagnostic technique will indicate a negative test result when the condition is absent (true negative).
).

References

• Black, S.E., Vu, B., Martin, D., & Szalai, J.P. (1990). Evaluation of a bedside battery for hemispatial neglect in acute stroke [Abstract]. Journal of Clinical and Experimental Neuropsychology, 12, 109.
• Black, S., Ebert, P. L., Leibovitch, F., Szalai, J. P., & Blair, N. (1995). Recovery in hemispatial neglect [Abstract]. Neurology, 45(suppl 4), A178.
• Black, S. E., Leibovitch, F. S., Ebert, P. L., & L., B. K. (2016). SNAP : Sunnybrook Neglect Assessment Procedure Administration and Scoring Manual.
• Eskes, G.A., Butler, B., McDonald, A., Harrison, E.R., & Phillips, S.J. (2003). Limb activation effects in hemispatial neglect. Archives of Physical Medicine and Rehabilitation, 84, 323-8.
• Leibovitch, F.S., Black, S.E., Caldwell, C.B., Ebert, P.L., Ehrlich, L.E., & Szalai, J.P. (1998). Brain-behaviour correlations in hemispatial neglect using CT and SPECT: the Sunnybrook stroke study. Neurology, 50, 901-8.
• Leibovitch, F. S., Vasquez, B. P., Ebert, P. L., Beresford, K. L., & Black, S. E. (2012). A short bedside battery for visuoconstructive hemispatial neglect: Sunnybrook Neglect Assessment Procedure (SNAP). Journal of Clinical and Experimental Neuropsychology, 34(4), 359-68. doi:10.1080/13803395.2011.645016
• Menon-Nair, A., Korner-Bitensky, N., & Ogourtsova, T. (2007). Occupational Therapists’ identification, assessment, and treatment of unilateral spatial neglect during stroke rehabilitation in Canada. Stroke, 38, 2556-62. DOI: 10.1161/STROKEAHA.107.484857

See the measure

How to obtain the SNAP

The SNAP administration and scoring manual and test booklet can be accessed here.