Quantifying the Error Associated with Alternative GIS-based Techniques to Measure Access to Health Care Services

The aim of this study was to quantify the error associated with different accessibility methods commonly used by public health researchers. Network distances were calculated from each household to the nearest GP our study area in the UK. Household level network distances were assigned as the gold standard and compared to alternate widely used accessibility methods. Four spatial aggregation units, two centroid types and two distance calculation methods represent commonly used accessibility calculation methods. Spearman's rank coefficients were calculated to show the extent which distance measurements were correlated with the gold standard. We assessed the proportion of households that were incorrectly assigned to GP for each method. The distance method, level of spatial aggregation and centroid type were compared between urban and rural regions. Urban distances were less varied from the gold standard, with smaller errors, compared to rural regions. For urban regions, Euclidean distances are significantly related to network distances. Network distances assigned a larger proportion of households to the correct GP compared to Euclidean distances, for both urban and rural morphologies. Our results, stratified by urban and rural populations, explain why contradicting results have been reported in the literature. The results we present are intended to be used aide-memoire by public health researchers using geographical aggregated data in accessibility research.

Validity of the PULSES profile compared with the Functional Independence Measure for measuring disability in a stroke rehabilitation setting

OBJECTIVES

To test the validity of the PULSES profile for measuring the disability of stroke rehabilitation patients and to compare it with the Functional Independence Measure (FIM); and to determine the ability of the PULSES score to predict discharge home from a stroke rehabilitation setting.

STUDY DESIGN

Retrospective cohort.

SETTING

A tertiary stroke rehabilitation unit.

PATIENTS

One hundred ninety-seven patients admitted consecutively to a stroke rehabilitation unit from September 1992 to April 1995.

METHODS

The PULSES profile was tested for internal consistency. Criterion validity was evaluated by comparing with the FIM. Construct validity was tested using the multimethod-multitrait matrix method and by performing logistic regression to determine if admission PULSES score was predictive of discharge home.

RESULTS

Internal consistency of the PULSES profile was supported with a Cronbach's alpha of .74. There was a high correlation between the PULSES and FIM admission and discharge scores of -.82 and -.88, respectively. The multimethod-multitrait matrix correlations demonstrated good convergent and divergent validity for the correlation of the PULSES profile items and the FIM subcategories. Multivariate logistic regression determined the admission PULSES total score to be an independent variable in the model to predict discharge home.

CONCLUSIONS

The PULSES profile is a valid measure for assessing disability in the stroke rehabilitation setting. The PULSES profile correlates highly with the FIM. The admission PULSES total score is predictive of discharge home from a stroke rehabilitation program.

Attentional deficits in stroke patients: a visual dual task experiment

OBJECTIVE

(1) To compare the performance of subjects who have suffered a single lateralized cortical, ischemic stroke versus controls on measures of attention including a computerized dual visual attentional task to determine if this task is more sensitive for detecting the presence of subtle hemi-inattention compared to traditional attention tasks; (2) to determine if there is evidence of hemi-inattention in persons who completed spontaneous neurological recovery after a cortical, ischemic stroke compared to controls.

SUBJECTS

Thirty-six patients (N = 20 Right Hemisphere and N = 16 Left Hemisphere) who had previously undergone stroke rehabilitation and who were at least 1 year poststroke. All patients were currently living in the community. A control group of 20 subjects was recruited from the community.

RESULTS

There was no difference in performance between the three groups on gross clinical testing for hemi-inattention, or on the traditional letter-cancellation tasks. All subjects also participated in two computer generated tasks: (1) tracking a moving stimulus and (2) detecting briefly appearing targets. On the single task performance the control group performed significantly better than both cerebrovascular accident (CVA) groups (p < .004), but with no trend for hemi-inattention in any individual group. When the two computer tasks were combined, there was a significant difference in performance between the control group and all stroke subjects (p < .02) for target detection. A fatiguing effect over time was also found in the right CVA group on the dual task. Stroke subjects driving at the time of data collection performed better on the dual attentional task compared to stroke subjects not driving (p = .05).

CONCLUSIONS

On single and dual dynamic computerized visual attentional tasks, individuals who have suffered a cortical stroke more than 1 year before testing have significantly impaired attention compared to controls.