Reliability and stability of the orthodontic Patient Cooperation Scale

Patient cooperation is recognized as an important factor in the outcome of orthodontic treatment. In order to predict patient cooperation, there have been numerous studies which have examined its correlates in orthodontic treatment. However, few, if any, of these studies have considered the reliability or stability of their patient cooperation measures. Hence, the correlates found or not found are suspect. The present article reports on the internal consistency and stability of the Orthodontic Patient Cooperation Scale (OPCS). Using the responses of practicing orthodontists, a list was generated of ten patient behaviors frequently considered in evaluating a patient's cooperation. Subjects were eighth- and ninth-grade students undergoing orthodontic treatment, who were rated by their own orthodontists after 2 months and 6 months of treatment. The internal consistency for the scale was estimated to be 0.71 (N = 44) at 2 months and 0.80 (N = 45) at 6 months. The correlation between scores at 2 months and at 6 months was 0.58 (N = 44), which may be considered to be a conservative estimate of the long-term stability of the scale. In summary, the OPCS has adequate internal consistency and reasonably stable scores over a 4-month period. As such, it should prove useful in studies looking for predictors of patient cooperation and in studies examining the relationship of patient cooperation and outcome of treatment.