Can the Northwick Park Dependency Scale be translated to a Barthel Index?
OBJECTIVE
to develop and test an algorithm for conversion of the Northwick Park Dependency Scale (NPDS) to a Barthel Index.


METHODS
conversion criteria were developed to derive a Barthel Index from NPDS data. The criteria were then applied in two community-based datasets of NPDS and Barthel scores, gathered from carers/patients via postal questionnaires. A retrospective exploratory analysis (dataset A) was followed by prospective confirmatory analysis (dataset B).


METHODS
patients with neurological disabilities, mainly following acquired brain injury: dataset A (n = 225) and dataset B (n = 96).


METHODS
comparison of NPDS-derived Barthel scores with parallel directly rated Barthel scores.


RESULTS
the exploratory analysis identified that one Barthel item ('Stairs') could not be derived from the NPDS items alone, and required minor adaptation of one of the five additional questions that are included to translate the NPDS into an assessment of community care needs (Northwick Park Care Needs Assessment, NPCNA). For the prospective confirmatory analysis, the NPCNA 'Stairs' question was adjusted to support full conversion. Very strong intraclass correlations were observed between the total 'direct' and 'derived' Barthel scores (0.97 (dataset A), 0.95 (dataset B), P<0.001); 95% limits of agreement ranged from -2.52 to 2.56 (dataset A) and -3.29-3.91 (dataset B). Item-by-item agreement (linear-weighted Cohen's kappa coefficients) ranged from 0.68 to 0.85 (dataset A) and 0.59-0.83 (dataset B), which represents 'substantial' to 'almost perfect' agreement.


CONCLUSIONS
this study demonstrates that a Barthel Index can be reliably derived from NPDS and NPCNA data through a conversion algorithm which has now been built into the supporting software package.
Turner-Stokes
Lynne
L
King's College London, School of Medicine, Department of Palliative Care, Policy and Rehabilitation and Regional Rehabilitation Unit, Northwick Park Hospital. lynne.turner-stokes@dial.pipex.com
Williams
Heather
H
Howley
Deirdre
D
Jackson
Diana
D
D000203:Activities of Daily Living; D000465:Algorithms; D001930:Brain Injuries / Q000534:rehabilitation*; D004185:Disability Evaluation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D020380:Needs Assessment; D011446:Prospective Studies; D011594:Psychometrics; D015203:Reproducibility of Results; D012189:Retrospective Studies; D000071939:Stroke Rehabilitation; D006113:United Kingdom