Objective

Judgment of Line Orientation (JOLO) test is widely used in assessing visuospatial deficits in Parkinson's disease (PD). The neuropsychological assessment battery (NAB) offers the Visual Discrimination test, with age and education correction, parallel forms, and co-normed standardization sample for comparisons within and between domains. However, NAB Visual Discrimination has not been validated in PD, and may not measure the same construct as JOLO.

Method

A heterogeneous sample of 47 PD patients completed the JOLO and NAB Visual Discrimination within a broader neuropsychological evaluation. Pearson correlations assessed relationships between JOLO and NAB Visual Discrimination performances.

Results

Raw and demographically corrected scores from JOLO and Visual Discrimination were only weakly correlated. NAB Visual Discrimination subtest was moderately correlated with overall cognitive functioning, whereas the JOLO was not.

Conclusions

Despite apparent virtues, results do not support NAB Visual Discrimination as an alternative to JOLO in assessing visuospatial functioning in PD.

Introduction

Individuals with Parkinson's disease (PD) often exhibit deficits in visuospatial skills that can predict the presence or future development of PD dementia (García-Díaz, Segura, Baggio, & Junqué, 2013; Hughes et al., 2000; Janvin, Aarsland, Larsen, & Hugdahl, 2003). Visuospatial impairment can also help to differentiate idiopathic PD from atypical parkinsonism (Ballard et al., 1999; Noe et al., 2004) and may predict post-operative outcomes of deep brain stimulation surgery (Abboud et al., 2015). Thus far, the Judgment of Line Orientation (JOLO) test (Benton, Varney, & deS Hamsher, 1978) has been one of the most commonly used visuospatial measures and performance is commonly abnormal in PD compared with controls (Goldenberg, Wimmer, Auff, & Schnaberth, 1986). The JOLO is one of the few visuospatial tests recommended by the Movement Disorders Society Task Force for the assessment of mild cognitive impairment and dementia in PD (Litvan et al., 2012).

The JOLO's psychometric properties have been well established (Benton et al., 1978) and performance on this test has been linked to right hemisphere, especially parietal lobe dysfunction in a number of patients with brain injuries (Benton et al., 1978; Irani, 2011). Findings of excellent split-half reliability, ranging from 0.89 to 0.94 (Benton et al., 1978), have led to validation of a shorter version of the original (i.e., 15 vs. 30 items) that reduces fatigue and time burden. The short version of the JOLO has demonstrated comparable internal consistency and validity as the 30-item version of the test (Qualls, Bliwise, & Stringer, 2000; Woodard et al., 1996).

The Visual Discrimination subtest from the neuropsychological assessment battery (NAB) provides a comparable visuospatial task to the JOLO, with the advantage that the NAB provides a comprehensive suite of standardized tests that are co-normed for age and education and has alternate forms to reduce practice effects in test–retest scenarios (White & Stern, 2003). The Visual Discrimination subtest from the NAB is an 18-item task of visuo-perception where the patient must accurately match one of four subtly different geometric shapes to a target shape. However, the extent to which the Visual Discrimination test actually correlates with performance on the traditional JOLO test is unknown. The goal of this study was to assess the magnitude of association between a commonly used measure of visuospatial functioning in PD, the JOLO, and a newer test (Visual Discrimination from the NAB) that provides more comprehensive normative data.

Methods

Participants were adults with PD enrolled in a study examining saccadic eye movements. Diagnosis of idiopathic PD (Hughes, Daniel, Kilford, & Lees, 1992) was conferred by a fellowship-trained movement disorders neurologist; exclusion criteria were uncorrected vision disorders, prior deep brain stimulation, and evidence of comorbid neurological disorder or dementia other than that related to PD (e.g., no evidence of comorbid Alzheimer's dementia), by history or neuropsychological test results. Participants completed the 15-item JOLO and NAB Visual Discrimination in the course of a comprehensive neuropsychological evaluation structured to be consistent with Movement Disorders Society Task Force Level II criteria for diagnosing mild cognitive impairment and dementia in PD (Dubois et al., 2007; Litvan et al., 2012). Administration order of the JOLO and NAB visual discrimination was counterbalanced across participants. Participants provided informed consent, and research was conducted under the auspices of the local human research protection program.

All participants providing valid data on both measures were included in this analysis, regardless of cognitive status. A total of 47 participants were thus included for analysis. Table 1 contains demographic and disease-specific characteristics for the sample.

Table 1.

Demographic, disease-specific, and cognitive data for the patient sample

 Mean (N = 47) SD Range 
Age 65.98 8.87 44–82 
Sex 30 men/17 women  
Education 16.43 2.71 12–24 
Disease duration 7.14 4.69 0.6–23 
Hoehn Yahra 
 Stage 1 6.4%   
 Stage 1.5 10.6%   
 Stage 2 55.3%   
 Stage 2.5 8.5%   
 Stage 3 6.4%   
 Stage 4 4.3%   
 Stage 5 2.1%   
Cognitive status 
 No diagnosis n = 32   
 Mild cognitive impairment n = 14   
 PD dementia n = 1   
NAB visual discrimination (raw) 15.43 2.36 7–18 
NAB visual discrimination (z-score) −0.01 0.96 −2.33 to 1.28 
JOLO (raw) 11.75 2.37 6–15 
JOLO (z-score) 0.31 0.91 −2.05 to 1.08 
 Mean (N = 47) SD Range 
Age 65.98 8.87 44–82 
Sex 30 men/17 women  
Education 16.43 2.71 12–24 
Disease duration 7.14 4.69 0.6–23 
Hoehn Yahra 
 Stage 1 6.4%   
 Stage 1.5 10.6%   
 Stage 2 55.3%   
 Stage 2.5 8.5%   
 Stage 3 6.4%   
 Stage 4 4.3%   
 Stage 5 2.1%   
Cognitive status 
 No diagnosis n = 32   
 Mild cognitive impairment n = 14   
 PD dementia n = 1   
NAB visual discrimination (raw) 15.43 2.36 7–18 
NAB visual discrimination (z-score) −0.01 0.96 −2.33 to 1.28 
JOLO (raw) 11.75 2.37 6–15 
JOLO (z-score) 0.31 0.91 −2.05 to 1.08 

aHoehn Yahr staging for PD, where 1 represents the most mild and 5 represents the most severe disease stage. Patients spend the longest amount of time in HY stage 2 (Hoehn & Yahr, 1998).

Data were assessed for outliers and normative distribution. There were no significant outliers (absolute value of z-score >3); therefore, Pearson correlations were used to examine relationships between raw and standardized score performance on the JOLO and NAB Visual Discrimination tests. Performances on the JOLO were converted to percentiles using the Benton norms (adjusting for age and gender) and then back-converted to z-scores from percentiles. We assessed for potential discrepancy in the magnitude of relationship between raw and standardized scores between the two measures, which would highlight the influence of education correction. For the same reason, correlations among raw scores on each measure and the demographic variables of age, education, and sex were examined. To determine whether performances on these measures were related to an indicator of global cognitive ability, Pearson correlation analyses were conducted between the JOLO, Visual Discrimination, and total score from the Mattis Dementia Rating Scale (DRS-2) (Jurica, Leitten, & Mattis, 2004).

Results

Tables 2 and 3 provide results of correlation analyses. The simple product-moment correlation between raw scores on the JOLO and NAB Visual Discrimination was weak but significant, r = 0.31, p < .05. Post hoc power analysis suggested that a sample size of n = 47 would have detected a veritable, modest correlation of 0.6 between the two measures with power greater than 0.99; thus the current sample was believed to be adequately powered. The correlation between z-scores for JOLO and NAB Visual Discrimination subtests was not significant. Although both measures include age-based correction, age was not significantly correlated with performance in this sample of PD patients. Both measures were modestly correlated with education (JOLO-education: r = 0.32, p < .05; NAB-VISD-education: r = 0.35, p < .05). Partial correlation analysis examined the influence of education correction on the strength of relationship between the JOLO and NAB Visual Discrimination. Controlling for education effects, the absolute magnitude of the relationship between measures actually decreased and was not statistically significant, r = 0.22, p = .15. Finally, NAB Visual Discrimination evinced a modest, statistically significant correlation with DRS-2 total score, whereas JOLO performance did not.

Table 2.

Pearson correlations between Judgment of Line Orientation (JOLO), NAB Visual Discrimination (NAB-VISD), Dementia Rating Scale (DRS-2) raw scores, and standardized (z) scores

 NAB Visual Discrimination (raw) JOLO (raw) NAB Visual Discrimination (z-score) JOLO (z-score) 
JOLO (raw) 0.31*    
NAB Visual Discrimination (z-score) 0.96** 0.3*   
JOLO (z-score) 0.19 0.94** 0.22  
DRS-2 (raw) 0.42** 0.17 0.45** 0.09 
 NAB Visual Discrimination (raw) JOLO (raw) NAB Visual Discrimination (z-score) JOLO (z-score) 
JOLO (raw) 0.31*    
NAB Visual Discrimination (z-score) 0.96** 0.3*   
JOLO (z-score) 0.19 0.94** 0.22  
DRS-2 (raw) 0.42** 0.17 0.45** 0.09 

Notes: *Correlation is significant at the 0.05 level (two-tailed). **Correlation is significant at the 0.01 level (two-tailed).

Table 3.

Pearson correlations between Judgment of Line Orientation (JOLO), NAB Visual Discrimination (NAB-VISD) raw scores, and demographic variables

 Age Education Sex 
JOLO (raw) 0.01 0.32* −0.11 
p-value 0.93 0.03 0.46 
NAB Visual Discrimination (raw) −0.27 0.35* −0.15 
p-value 0.06 0.02 0.32 
 Age Education Sex 
JOLO (raw) 0.01 0.32* −0.11 
p-value 0.93 0.03 0.46 
NAB Visual Discrimination (raw) −0.27 0.35* −0.15 
p-value 0.06 0.02 0.32 

Note: *Correlation is significant at the 0.05 level (two-tailed).

Discussion

Weak bivariate correlations between both raw and demographically corrected scores indicate that NAB Visual Discrimination and JOLO measure different constructs. These results suggest that the JOLO and Visual Discrimination subtests are measuring different cognitive processes in patients with PD. Furthermore, performance on both measures was significantly influenced by education; however, controlling for education effects did not improve the correlation between the two measures.

In this sample of PD patients, JOLO performance was influenced by education level. Our results are consistent with findings from a study by Gullett and colleagues (2013) examining reliability of split-half, two-thirds, and full (30 item) versions of the JOLO in PD patients. Those authors also found association between age and performance. Taken together, these findings highlight the need for age and education-based normative data derived from healthy adults. Despite its potential given the existence of age and education-corrected norms, weak correlation with JOLO suggests that NAB Visual Discrimination subtest may not provide a viable substitute.

Based on these findings, it remains somewhat unclear whether the JOLO or Visual Discrimination subtest is superior in measuring visuospatial functioning in PD patients. However, the JOLO has superior test–retest reliability (r  = 0.90) (Benton et al., 1978) compared with NAB Visual Discrimination (r  = 0.37) (White & Stern, 2003). It should be noted that test–retest reliability data are not available for the 15-item JOLO version, which was administered in this study and is often used in older adult, neurologically compromised patients. In patients with PD, test–retest reliability for the (30-item) JOLO has been estimated to be at least r = 0.73 (Muslimović, Post, Speelman, De Haan, & Schmand, 2009). Although potential practice effects in healthy adults are minimal in both tests, lack of practice effects for the JOLO has been demonstrated in PD (Montse, Pere, Carme, Francesc, & Eduardo, 2001). A recent analysis by Goldman and colleagues also supported the JOLO for assessing visuospatial functioning in PD (Goldman et al., 2015). Given its superior psychometric properties and wide use in PD, the JOLO appears to be the measure of choice for assessing visuospatial functioning in PD. If this is assumed to be true, the significant relationship between Visual Discrimination subtest and DRS-2 total scores in PD patients may suggest that the Visual Discrimination subtest of the NAB simply has poor discriminant validity, and lower scores are indicative of generally poor cognitive functioning, but not specific to visuospatial impairment.

Interpretation of the present findings is limited by lack of additional visuospatial measures within the cognitive battery for comparison of performances. The present sample size also precludes comparisons between groups on other potentially relevant clinical phenomena, such as presence of visual illusions/hallucinations or REM sleep behavior disorder. However, the sample included in this study was adequately powered to avoid Type-I and Type-II errors; more importantly, it was heterogeneous with respect to duration of illness, HY stage, and global cognitive function (DRS-2 score) to reflect the broader population of individuals with PD undergoing neuropsychological examinations and enrolled in clinical trials. Future studies would do well to examine ecological validity of JOLO and other visuospatial tasks in PD with respect to instrumental activities of daily living such as driving, organizing personal items, and performing simple household assembly and repair tasks.

Funding

This work was supported by the Michael J. Fox Foundation.

Conflict of Interest

None declared.

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