[Use of trajectories for measuring change in medical rehabilitation: a contribution toward comparison of different methods of outcome measurement].
OBJECTIVE
The question of which methods should be used to assess the effects of medical rehabilitation has a long and controversial history. With regard to this background the project "Outcome measurement in medical rehabilitation" aimed at developing a better understanding of the process of change and its assessment. We also looked into possible causes for discrepancies between the results of direct and indirect measures of change. Aims of our study were: (1) to picture trajectories of change in a simple and descriptive way, (2) to compare the resulting solutions, (3) to highlight relations with direct measurement of change and/or global estimation of effects, (4) to compare the predictive value of different measurements of change.


METHODS
We used available data from rehabilitation research which covered direct and indirect measurement of change as well as global measurement of effects and which therefore enabled us to compare different methods of outcome measurements. The well documented record includes data from n=466 patients with chronic back pain. Different trajectories (3 and 5 groups) were defined using their pre/post data.


RESULTS
Depending on limits chosen for positive or negative courses and chosen outcome 20% to almost 40% of the patients showed improvements over the follow-up period. About the same percentages changed for the worse. However, two-thirds of the patients improved at least in one outcome. Compared with those, who did not experience improvements in any outcome, this group indicated better global rehabilitation effects. The different types of trajectories (3 and 5 groups) substantially contribute to the explained variance of catamnestic status at 12 months beyond other predictors as well as beyond initial status. The same applies to the prediction of disability days.


CONCLUSIONS
The description of trajectories of change yields useful results. In contrast to complex statistical methods we were able to identify groups of patients that can easily be described.
Abteilung Qualitätsmanagement und Sozialmedizin (AQMS), Universitätsklinikum Freiburg, Freiburg, Germany. cornelia.meffert@uniklinik-freiburg.de
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Meffert
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Kohlmann
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Raspe
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Gerdes
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Mittag
D001416:Back Pain / Q000175:diagnosis* / Q000453:epidemiology / Q000534:rehabilitation*; D002908:Chronic Disease; D023381:Endpoint Determination / Q000379:methods*; D005260:Female; D005858:Germany / Q000453:epidemiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D017063:Outcome Assessment, Health Care / Q000379:methods*; D010147:Pain Measurement / Q000379:methods* / Q000706:statistics & numerical data*; D015995:Prevalence; D015203:Reproducibility of Results; D012307:Risk Factors; D012680:Sensitivity and Specificity