تجزیه و تحلیل مقیاس اضطراب در بیماری پارکینسون

Objective Anxiety is a common non-motor symptom in Parkinson's disease (PD). This study analyzed the measurement properties of three frequently used anxiety scales in PD: the Beck Anxiety Inventory (BAI), the Hamilton Anxiety Rating Scale (HARS), and the Hospital Anxiety and Depression Scale—Anxiety subscale (HADS-A). Method The Rasch model was applied to a multicenter international cohort of 342 patients and assessed the following aspects: fit to the Rasch model, unidimensionality, reliability, response category ordering, item local independence, differential item functioning, and scale targeting. Results In their original form, the BAI, HARS, and HADS-A, did not fit the Rasch model. A good fit to the Rasch model was only found after significant modifications, including rescoring some items and deleting those failing to fit the model. For the BAI and HADS-A, these adjustments resulted in unidimensionality. The HARS was not unidimensional and separate analyses were performed for its psychic and somatic subscales. Whereas the somatic anxiety subscale fit the Rasch model, this was achieved for the psychic anxiety subscale after modifications. Conclusion None of the currently used anxiety scales display satisfactory measurement properties for assessing anxiety in PD. The results suggest the need to develop a new disease-specific scale for measuring anxiety in PD.

Parkinson's disease (PD) is a neurodegenerative disorder characterized by motor dysfunction as well as a high prevalence of neuropsychiatric disturbances including depression, anxiety, psychosis and cognitive decline. For clinical and research care, it is critical that valid and reliable scales are available to assess neuropsychiatric symptoms in patients with PD [1]. Anxiety is one of the most prevalent psychiatric symptoms in PD; up to 34% of all PD patients suffer from an anxiety disorder, as defined by DSM-IV-TR criteria [2] and [3]. Several generic anxiety scales have been used as screening and assessment tools in PD patients, but there are no specific tools for use in the PD population. Two well-known and commonly used anxiety scales in the psychiatric and general population, the Beck Anxiety Inventory (BAI) [4], and the Hospital Anxiety and Depression Scale-Anxiety subscale (HADS-A) [5], were recognized as “suggested” scales for screening by a Movement Disorders Society task force evaluating anxiety rating scales for PD patients. The task force classified another anxiety scale, the Hamilton Anxiety Rating Scale (HARS) [6], as a “suggested” scale for measuring the severity of anxiety symptoms. No anxiety scale met the criteria for “recommended”, mainly because of the absence of validation studies in PD samples [3]. Recent validation studies of these anxiety scales in PD patients demonstrated good results for some, but not all, parameters [7], [8], [9], [10] and [11]. All studies but one [7] used a classic test theory (CTT) approach. CTT assumes that each person has a true score, which would be obtained if there were no error in the measurements. A draw-back of CTT, however, is that item and person statistics are sample-dependent, and neither the true score not the measurement error can be determined accurately [12]. Traditionally, CTT studies report on reliability, validity and sensitivity to change (along with acceptability and other parameters), mostly based on correlational and mean-difference analyses. The application of the Rasch measurement model [13], combined with the CTT approach, is currently considered the standard for developing and assessing patient outcome report measures [12]. According to the Rasch model, the probability that a person will give a certain response is a logistic function of the difference between the person's ability and the item parameter [13]. For anxiety scales, the person's ability is the experienced anxiety level and the item parameter represents the level of anxiety assessed by that item. Rasch analysis and CTT provide information on different psychometric aspects of the measure. Thus, both approaches are important to have insight in the qualities of the scale. Most questionnaires developed from a CTT approach use raw sum-scores, which are at the ordinal level. Scales that fit the Rasch model provide results in a linear scale, which allows the use of parametric statistics and the calculation of change scores. Excellent tutorials for Rasch analysis applied to health scales are available [14], [15] and [16]. This study used Rasch analysis to explore and report the measurement properties of three commonly used anxiety scales in PD. The main hypothesis tested in this study is that the BAI, HARS and HADS-A fit the Rasch model and show adequate measurement properties when applied to PD patients. Specifically, the following parameters were analyzed for each scale: fit to the Rasch model, reliability, appropriateness of the response scale, local independence of items, item bias, and scale targeting. In case the scales do not fit the Rasch model, appropriate modifications will be proposed and assessed. A previous study, using the same data set, focused on psychometric properties of the scales under the CTT paradigm [9].