Classification of patients with whiplash associated disorders (WAD): reliable and valid subgroups based on the Multidimensional Pain Inventory (MPI-S).
BACKGROUND
Classification of patients with chronic whiplash associated disorders (WAD) into homogenous subgroups is an important objective in order to tailor interventions and to control for subgroup differences when evaluating treatment outcome.


OBJECTIVE
The aims of this study were to investigate if it was possible to replicate and describe the three cluster solution and profiles found in other pain groups and describe cluster profiles based on self-reported Multidimensional Pain Inventory-scores for patients with WAD three months after the injury, describe characteristics of the clusters in relation to disability, self-efficacy and coping at the same point in time and to validate the cluster solution by comparing clusters in disability, self-efficacy and coping over time.


METHODS
Ninety-one WAD-patients three months after the accident took part in the study. The measures used were the Multidimensional Pain Inventory-Swedish version (MPI-S), The Self-Efficacy Scale, The Coping Strategies Questionnaire and The Pain Disability Index. Cluster analysis was conducted for the total sample MPI-S subscale scores.


RESULTS
The adaptive copers cluster represented 42% of the sample, dysfunctional 34% of the sample, and interpersonally distressed 24% of the sample. The external validation of cluster solution showed that there were several significant differences between clusters in self-efficacy, disability and coping measures. There was also a significant interaction effect (clusterxtime) in disability (PDI). Patients in dysfunctional cluster reported a decreased disability over time.


CONCLUSIONS
These results support the presence of different subgroups among patients with whiplash associated disorders. This classification can be seen as a complement to a classification based on medical condition.
Söderlund
Anne
A
Department of Public Health and Caring Science/Section of Caring Sciences, Uppsala University, Uppsala Science Park, S-75 183 Uppsala, Sweden. anne.soderlund@pubcare.uu.se
Denison
Eva
E
D000223:Adaptation, Psychological; D000328:Adult; D000704:Analysis of Variance; D016000:Cluster Analysis; D004185:Disability Evaluation; D005260:Female; D006801:Humans; D008297:Male; D010147:Pain Measurement / Q000592:standards*; D011584:Psychology; D015203:Reproducibility of Results; D020377:Self Efficacy; D011795:Surveys and Questionnaires; D014911:Whiplash Injuries / Q000145:classification* / Q000523:psychology*