PURPOSE: To construct and validate a prediction instrument for early identification of patients with a high risk of delayed recovery after whiplash injuries (PPS-WAD) in an insurance company setting.
METHODS: Prospective cohort study. On the basis of a historic cohort (n = 130) of patients with a whiplash injury identified in an emergency room (ER, model-building set), we used logistic regression to construct an instrument consisting of two demographic variables (i.e. questions of educational level and work status) and the patient-rated physical and mental status during the acute phase to predict self-reported nonrecovery after 6 months. We evaluated the instrument's ability to predict nonrecovery in a new cohort (n = 204) of patients originating from an insurance company setting (IC, validation set).
RESULTS: The prediction instrument had low reproducibility when the setting was changed from the ER cohort to the IC cohort. The overall percentage of correct predictions of nonrecovery in the ER cohort was 78 % compared with 62 % in the IC cohort. The sensitivity and specificity in relation to nonrecovery were both 78 % in the ER cohort. The sensitivity and specificity in the insurance company setting was lower, 67 and 50 %.
CONCLUSION: Clinical decision rules need validation before they are used in a new setting. An instrument consisting of four questions with an excellent possibility of identifying patients with a high risk of nonrecovery after a whiplash injury in the emergency room was not as useful in an insurance company setting. The importance and type of the risk factors for not recovering probably differ between the settings, as well as the individuals.