A Rasch-based validation of the Hooper Visual Organization Test in Chinese-speaking children

The aim of this study was to examine the validation of the Hooper Visual Organization Test (HVOT) for use in children by testing for item fit, unidimensionality, item hierarchy, reliability, and screening capacity. A modified scoring system was devised for the HVOT so that children received some credit for being able to describe the function of objects. The HVOT was administered to 630 typically developing school-aged children and 210 children with Down syndrome matched for age and education. Rasch analysis and receiver operating characteristic curve were applied.Rasch analysis of data from typically developing children showed that twelve items were candidates for deletion due to poor fit to the Rasch model, violation of normality and age-related item bias. Removing these items resulted in a shortened version with 18 items that forms a reliable and strong unidimensional, hierarchical scale. The items were well targeted to the ability level of the children tested. Area under the curve for HVOT-18 was 0.84, indicating very good ability to identify visual integration deficit in children with Down syndrome. The 18-item HVOT can be summed to produce an overall index of visual synthetic ability. Subsequent work is needed to validate its use in other childhood disabilities.     

Assessing autonomic symptoms of Parkinson’s disease with the SCOPA‐AUT: a new perspective from Rasch analysis

Background: The Scale for Outcomes in Parkinson’s disease (PD) for Autonomic Symptoms (SCOPA‐AUT) is a specific scale to assess autonomic dysfunction in PD patients. It was developed and validated under the classic test theory approach. This study sought to test whether the SCOPA‐AUT meets item response theory standards for reliability, internal construct validity, response category ordering, and differential item functioning by gender and age group. Method: The Rasch measurement model was applied to a sample of 385 PD patients. Results: Model fit was obtained after the response categories were rescored and item 10‐Incomplete emptying deleted because of redundancy. Person separation index, a reliability measure, was 0.82. All but two items (2‐Sialorrhea and 13‐Nocturia) were free of gender‐ and age‐related bias. The strict tests of unidimensionality were met, indicating the validity of the total sumscore. Scale targeting suggested the need for items representing milder autonomic symptoms. Conclusions: Suggestions for improving the SCOPA‐AUT include a shorter scale with a simpler response scheme and a combination of sexual items for men and women. The resulting SCOPA‐AUT is a reliable scale, with good internal construct validity, providing Rasch transformed results on a linear metric scale.     

A new look at the construct validity of the K6 using Rasch analysis

The Kessler six‐item psychological distress (K6) scale is widely used to screen for mental disorders; however, information is lacking on the rating scale performance or dimensionality structure of the scale. This study used a population based sample (n = 7596) to evaluate the construct validity of the K6 scale using Rasch partial credit analysis. The analysis showed that almost all of the five‐point rating scales in the K6 items were used appropriately to differentiate psychological distress of the study participants. The analysis provided evidence of unidimensionality of the scale, although items 1 (so sad) and 3 (restless or fidgety) might offer a potential second off‐dimensional component. All items appeared to fit the Rasch model's expectation as demonstrated by the acceptable item fit statistics. The study participants demonstrated valid response patterns when answering K6 items, except for some who were younger or had higher psychological distress. This study using Rasch analysis confirms the construct validity of the K6 scale and suggests that the K6 is a useful and valid instrument for assessing psychological distress in the mid‐aged general population. Further research can facilitate better understanding about the unidimensionality of the scale. Copyright © 2014 John Wiley & Sons, Ltd.     

Fatigue and daytime sleepiness scale in myotonic dystrophy type 1

Introduction: Fatigue and excessive daytime sleepiness are frequent complaints in myotonic dystrophy type 1 (DM1) that often overlap. We aimed to construct a combined fatigue and daytime sleepiness rating scale for DM1 using the Rasch measurement model. Methods: Questionnaires, including the Epworth Sleepiness Scale, Fatigue Severity Scale, and Daytime Sleepiness Scale, were completed by 354 patients. Data were subjected to Rasch analyses and tested for required measurement issues such as appropriate response categories, absence of item bias, local independence, and unidimensionality. Results: The initial 22 items did not meet Rasch model expectations. After rescoring and removing misfitting items, the final 12‐item scale showed good model fit and unidimensionality. High internal consistency (person separation index = 0.80) and validity were demonstrated. Conclusions: The Rasch‐built Fatigue and Daytime Sleepiness Scale, developed specifically for DM1 patients, provides interval measures on a single continuum. Its use is suggested for future clinical trials and therapeutic follow‐up. Muscle Nerve, 2013     

Improving fatigue assessment in immune‐mediated neuropathies: the modified Rasch‐built fatigue severity scale

Abstract Fatigue is a major disabling complaint in patients with immune‐mediated neuropathies (IN). The 9‐item fatigue severity scale (FSS) has been used to assess fatigue in these conditions, despite having limitations due to its classic ordinal construct. The aim was to improve fatigue assessment in IN through evaluation of the FSS using a modern clinimetric approach [Rasch unidimensional measurement model (RUMM2020)]. Included were 192 stable patients with Guillain‐Barré syndrome (GBS), chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) or polyneuropathy associated with monoclonal gammopathy of undetermined significance (MGUSP). The obtained FSS data were exposed to RUMM2020 model to investigate whether this scale would meet its expectations. Also, reliability and validity studies were performed. The original FSS did not meet the Rasch model expectations, primarily based on two misfitting items, one of these also showing bias towards the factor ‘walking independent.’ After removing these two items and collapsing the original 7‐point Likert options to 4‐point response categories for the remaining items, we succeeded in constructing a 7‐item Rasch‐built scale that fulfilled all requirements of unidimensionality, linearity, and rating scale model. Good reliability and validity were also obtained for the modified FSS scale. In conclusion, a 7‐item linearly weighted Rasch‐built modified FSS is presented for more proper assessment of fatigue in future studies in patients with immune‐mediated neuropathies.     

Measuring disability across cultures — the psychometric properties of the WHODAS II in older people from seven low‐ and middle‐income countries. The 10/66 Dementia Research Group population‐based survey

We evaluated the psychometric properties of the 12‐item interviewer‐administered screener version of the World Health Organization Disability Assessment Schedule – version II (WHODAS II) among older people living in seven low‐ and middle‐income countries. Principal component analysis (PCA), confirmatory factor analysis (CFA) and Mokken analyses were carried out to test for unidimensionality, hierarchical structure, and measurement invariance across 10/66 Dementia Research Group sites. PCA generated a one‐factor solution in most sites. In CFA, the two‐factor solution generated in Dominican Republic fitted better for all sites other than rural China. The two factors were not easily interpretable, and may have been an artefact of differing item difficulties. Strong internal consistency and high factor loadings for the one‐factor solution supported unidimensionality. Furthermore, the WHODAS II was found to be a ‘strong’ Mokken scale. Measurement invariance was supported by the similarity of factor loadings across sites, and by the high between‐site correlations in item difficulties. The Mokken results strongly support that the WHODAS II 12‐item screener is a unidimensional and hierarchical scale confirming to item response theory (IRT) principles, at least at the monotone homogeneity model level. More work is needed to assess the generalizability of our findings to different populations. Copyright © 2010 John Wiley & Sons, Ltd.     

Evaluation of the structure of Brazilian State-Trait Anxiety Inventory using a Rasch psychometric approach

Objective

This study evaluates the State-Trait Anxiety Inventory (STAI) structure using a Rasch psychometric approach, and a refined and shorter STAI version is proposed.

Methods

A cross-sectional study was performed with 900 inpatients scheduled for elective surgery. Age varied from 18 to 60 years (American Society of Anesthesiologists physical status I-III). Demographic information was collected using a structured questionnaire. The measuring instrument (the STAI) was applied to all patients in the afternoon before the surgery and prior to the patients receiving preoperative sedatives.

Results

Rasch analysis of the state and trait anxiety scales was performed separately. This analysis demonstrated that the original format of state and trait scales fails to show invariance across the trait-state anxiety level, which results in the unstable performance of items. The refined scale was retested in two subsequent random samples of 300 subjects each, and the results were confirmed. The performance was adequate regardless of gender. In the analysis, some items of the state scale (items 3,4,9,10,12,15, and 20) were deleted due to poor fit statistics. The remaining 13 items showed unidimensionality, local independence, and adequate index of internal consistency. Also, the original trait scale displayed several weaknesses. First, the four-point Likert response scale proved to be inadequate, and threshold disorders were found in all 20 items. Also, the original trait scale showed insufficient item-trait interaction and several individual item misfits. Following the rescoring process, and retesting in a second random sample, items were excluded (namely Items 3, 4, 11, 13, 14, 15, 18, and 19). The refined version showed local independence, unidimensionality, and adequate fit statistics.

Discussion

The results indicate that the application of the Rasch model led to the refinement of the classic STAI state and trait scales. In addition, they suggest that these shorter versions have a more suitable psychometric performance and are free of threshold disorders and differential item functioning problems.     

Rasch analysis of the Developmental Test of Visual-Motor Integration in children with intellectual disabilities

The purpose of this study was to examine the measurement properties of the Developmental Test of Visual-Motor Integration (VMI) in children with intellectual disabilities (ID) ages 4–12 years using the dichotomous Rasch model. The VMI was administered individually to 454 children with ID. Rasch analysis was applied to investigate unidimensionality, item fit to the model, differential item functioning (DIF), and item targeting. Discriminative validity was obtained by receiver operating characteristic (ROC) curve analysis. Items were eliminated if the task was too easy or too difficult, or showed misfit to the Rasch model. The remaining items fitted the unidimensional construct the test was intended to measure and were free of DIF. The Rasch reduced version of the VMI with 9 items appeared to be suited to measure mild degrees of perceptual-motor impairment and demonstrated excellent reliability (0.91). VMI-9 had a larger area under the ROC curve in its ability to differentiate mild versus moderate to severe ID compared with the original version. Taken together, the VMI-9 provides a quick, reliable and valid measure for screening and identifying perceptual-motor deficits in children with ID.     

Can item response theory reduce patient burden when measuring health status in neurological disorders? Results from Rasch analysis of the SF-36 physical functioning scale (PF-10)

BACKGROUND: Indices of physical function may have a hierarchy of items. In cases where this can be demonstrated it may be possible to reduce patient burden by asking them to complete only those items which relate directly to their own level of ability. OBJECTIVES: To determine whether statistical procedures, operationalising what is known as item response theory (IRT), can be used to assess the unidimensionality of the 10 item physical functioning domain of the SF-36 in patients with Parkinson's disease and motor neuron disease, and, secondly, to determine whether it would be possible to administer subsets of items to certain patients, on the basis of their replies to other items in the scale, thereby reducing patient burden. METHODS: Rasch analysis, a form of IRT methodology, of the 10 item physical functioning domain (PF-10) in two neurological patient samples was undertaken and the results compared with results of a Rasch analysis of data gained from a population survey (the third Oxford healthy lifestyles survey). RESULTS: Evidence from the analyses suggests that the PF-10 does not form a perfect hierarchy on a unidimensional scale. However, certain items seem to form a hierarchy, and responses to some of them are contingent on responses to the other items. CONCLUSIONS: Rasch analysis of the PF-10 in neurological patients has indicated that certain items of the scale are hierarchically ordered, and consequently not all respondents would need to complete them all: indeed those most severely ill would be required to complete less items than those with only limited disabilities. The implications of this are discussed.     

Reliability,Validity, and Unidimensionality of the Korean Version of the Pornography Craving Questionnaire Based on the Classical Test Theory and Item Response Theory

ObjectiveThis study aimed to evaluate the reliability and validity of the Korean version of the Pornography Craving Questionnaire (K-PCQ) using classical test theory and item response theory. MethodsThe goodness of fit test and differential item functioning (DIF) analysis based on the Rasch model, confirmatory factor analysis (CFA), exploratory factor analysis (EFA), and correlation analysis were used to test its reliability and validity. ResultsResponse data from 226 students were analyzed. According to the goodness of fit test, the outfit mean square value of only one item, Item 11, was greater than 2. The CFA results revealed that all items of the K-PCQ measured a single construct. The EFA results revealed that the K-PCQ had excellent internal reliability. The DIF analysis results showed that the measurement of pornography craving using the K-PCQ did not differ based on gender. The result of Poly-DIMTEST supported the unidimensionality of the K-PCQ. The cut-off value of pornography craving was suggested as a measure of -0.0908 which corresponds to 46 (54.8%) out of a maximum score of 84. ConclusionThe items of the K-PCQ are unidimensional and have good reliability and validity. The K-PCQ will be useful in clinical practice and research as a screening tool for pornography craving.     

Gillette Functional Assessment Questionnaire 22-item skill set: factor and Rasch analyses

Aim To determine dimensionality and item‐level properties of the Gillette Functional Assessment Questionnaire (FAQ) 22‐item skill set using factor and Rasch analyses. Method A retrospective review of parent‐reported FAQ 22‐item skill set data was conducted of 485 individuals (273 males, 212 females; mean age 9y 10mo, SD 3y 10mo), including 289 with cerebral palsy and 196 with a variety of other neuromusculoskeletal conditions with orthopedic impairments. Factor analyses to validate unidimensionality of the skill set and Rasch analyses to determine relative item difficulty, item and test level information, and content coverage of the item set were performed. Differential item functioning analysis of sub‐groups based on sex, diagnosis grouping, and age was conducted. Precision of score estimates for the item set was analyzed. Results The FAQ 22‐item skill set demonstrates unidimensional structure and good item fit statistics. No floor or ceiling effects were noted. Differential item functioning (DIF) based on age was noted for seven items, four items showed diagnosis group‐related DIF, and one item sex‐related DIF. Precision was adequate in the mid‐range range of abilities. Interpretation Based on this analysis, the FAQ 22‐item skill set is a hierarchical set of interval scaled items suitable for measuring locomotor skill ability in children.     

Refinement of the SWN-20 based on the Rasch rating model

ObjectivesThe aim of the present study was to refine the 20-item Subjective Well-Being under Neuroleptic Treatment Scale (SWN-20) using the Rasch rating model to validate measurements of subjective well-being in patients with schizophrenia undergoing antipsychotic treatment.MethodsIn total, 854 (403 males, 451 females) inpatients (n = 213) and outpatients (n = 641) with schizophrenia participated in this study, which was designed as an open-label investigation of paliperidone extended release. The participants completed the Korean version of the SWN-20 themselves. Refinement of the Korean version of the SWN-20 was accomplished using the Rasch rating model.ResultsInfit and outfit statistics for all 20 items satisfied the criterion for construct validity. Second, all items except items 2 and 20 had suitable point–measure correlations, reflecting content validity. Third, item characteristic curves indicated that roughly 18 items were evenly distributed along the person ability continuum. Finally, option analysis of the category characteristics showed that categories 3 and 4 in the SWN-20 response format were unnecessary.ConclusionsWe offer several recommendations for improving the SWN-20: (a) items 2 and 20 should be omitted to ensure construct validity; (b) easier items would be added related to the person ability estimates in the process of validating a short form of the SWN scale based on item response theory; and (c) the number of response categories should be reduced for schizophrenic patients.     

Validity of the 36-item Persian (Farsi) version of the world health organization disability assessment schedule (WHODAS) 2.0

The purpose of this study was to validate a self-administered 36-item Persian (Farsi) version of the World Health Organization (WHO) Disability Assessment Schedule II (now referred to as WHODAS 2.0) for assessment of psychiatric patients’ perceptions of their functioning and disability. WHODAS 2.0 items were analyzed using two approaches. Reliability, consistency, and factor structure were assessed using Cronbach’s α and factor analysis, and item response theory (IRT) was used to determine how well the WHODAS 2.0 items fitted the Rasch paradigm. Data were collected from 614 psychiatric outpatients in Tehran. The mean overall disability score for the sample was 37.57. The scale had excellent reliability (Cronbach’s α?=?0.94). The IRT-based analysis showed that overall the set of items had a poor fit to the Rasch paradigm; the exceptions were items belonging to domains D1 (cognition), D2 (mobility), and D5 (life activities). There were several problematic items associated with dimensions D3 (self-care) and D4 (getting along). There were at least two badly fitted items associated with all dimensions. This study is the first to examine the psychometric properties of the self-administered, 36-item, Persian version of WHODAS 2.0 in psychiatric outpatients. This version has acceptable reliability and validity in psychiatric patients, but a reformulation of problematic items and further validation tests would be required to produce a robust measurement instrument.     

A validation analysis of two self‐reported HAM‐D6 versions

Objective: The six items of the clinician‐administrated Hamilton Depression Scale (HAM‐D₆) cover the core items of depressive states reflecting the antidepressive effect of medication. In this study, the two self‐reported versions of the HAM‐D₆ have been psychometrically validated to ensure the unidimensionality of this administration form in patients with mild‐to‐moderate depression. Method: The item response theory analysis of Mokken was used to test the unidimensionality of both the Interactive Voice Recording System (IVRS) version of the HAM‐D₆ and a paper‐and‐pencil self‐reported version (S‐HAM‐D₆). Patients with typical major depression and with seasonal affective disorder were included. Results: The Mokken analysis showed that the two self‐reported versions of the HAM‐D₆ obtained coefficients of homogeneity above 0.40, similar to the clinician‐rated HAM‐D₆ and thus implying unidimensionality. By contrast, the full HAM‐D₁₇ versions (self‐reported as well as clinician‐rated) obtained coefficients of homogeneity below 0.40, implying that the HAM‐D₁₇ is a multidimensional scale. Conclusion: The analysis show that both the IVRS version and the S‐HAM‐D₆ version are unidimensional self‐rating scales for the measurement of depressive states.     

Rating catatonia in patients with chronic schizophrenia: Rasch analysis of the Bush-Francis Catatonia Rating Scale

BACKGROUND: Catatonic signs and symptoms are frequently observed in patients with chronic schizophrenia. Clinical surveys have suggested that the composition of catatonic syndrome occurring in chronic schizophrenia may be different from what is found in acute psychiatric disorders or medical conditions. Consequently, this patient population may need tailor-made rating instruments for catatonia. The aim of the present study was to examine the suitability and accuracy of using the Bush-Francis Catatonia Rating Scale (BFCRS) in chronic schizophrenia inpatients. METHOD: The unidimensionality (optimal number of items; item fit), and the scoring scheme (the optimal number of scoring categories) of the BFCRS were determined in a random sample of 225 patients with chronic schizophrenia applying Rasch analysis. In addition, differential item functioning (DIF) analysis was also performed. RESULTS: The BFCRS proved to be unidimensional apart from three misfit and one marginally misfit items. The three misfit items were removed from the scale thereby constructing a revised version called BFCRS-R. Since the original BFCRS (BFCRS-O) showed no increase across items across steep gradients (poor endorsability of step calibrations), in BFCRS-R a binary scale ('absent' versus 'present' choices only) was constructed instead of the scoring scheme of 0-3.The 20-item BFCRS-R showed improved psychometric properties in that it had a higher item separation index than BFCRS-O. BFCRS-R mean logit was closer to zero indicating that the items on the scale and the subjects were better matched than in BFCRS-O. DIF analysis showed that certain items of both versions of BFCRS were influenced by the presence of negative symptoms. CONCLUSION: BFCRS-R is shorter and simpler than the original version and having better psychometric properties seems to be better suited for identifying and quantifying catatonia in chronic psychotic patients.     

Should the SCOPA‐COG be modified?: a Rasch analysis perspective

Background and purpose: The SCales for Outcomes in PArkinson’s disease‐Cognition (SCOPA‐COG) is a specific measure of cognitive function for Parkinson’s disease (PD) patients. Previous studies, under the frame of the classic test theory, indicate satisfactory psychometric properties. The Rasch model, an item response theory approach, provides new information about the scale, as well as results in a linear scale. This study aims at analysing the SCOPA‐COG according to the Rasch model and, on the basis of results, suggesting modification to the SCOPA‐COG. Method: Fit to the Rasch model was analysed using a sample of 384 PD patients. Results: A good fit was obtained after rescoring for disordered thresholds. The person separation index, a reliability measure, was 0.83. Differential item functioning was observed by age for three items and by gender for one item. Conclusions: The SCOPA‐COG is a unidimensional measure of global cognitive function in PD patients, with good scale targeting and no empirical evidence for use of the subscale scores. Its adequate reliability and internal construct validity were supported. The SCOPA‐COG, with the proposed scoring scheme, generates true linear interval scores.     

Psychometric properties of the Pediatric Motor Activity Log used for children with cerebral palsy

The Pediatric Motor Activity Log (PMAL) is a parent-report measure of the use, by children with hemiplegic cerebral palsy (CP), of their affected upper limb in everyday activities. The aim of this study was to examine the psychometric properties of both scales of the PMAL ('How Often' and 'How Well' scales) using Rasch measurement modelling. Sixty-one parents of children with hemiplegic CP completed the PMAL and 31 completed it again 3 weeks later. The mean age of children was 4 years 6 months (SD 1y 9mo); 35 males, 26 females. Children were at Gross Motor Function Classification System (GMFCS) levels I (83%) and II (17%), and Manual Ability Classification System levels I (35%), II (52%), and III (14%). The original scales were found to have disordered rating scale structure. Further Rasch modelling with collapsed rating scale structures resulted in both scales conforming to the expectations of the Rasch model, yielding strong evidence for construct validity and reliability. One item from the How Often scale failed to conform to Rasch expectations and was deleted in subsequent analyses. Test–retest reliability of both scales was high (the intraclass correlation coefficient for the How Often scale was 0.94, and for the How Well scale 0.93). The revised scales possess good psychometric properties, specifically a logical item hierarchy, evidence of unidimensionality, adequate rating scale structure, and good test–retest reliability. We conclude that the revised PMAL has the capacity to yield valid and reliable scores except for children at the extremes of upper limb ability.     

Improving assessment in small fiber neuropathy

Interval measures at the impairment level addressing symptoms and at the activity/participation level addressing daily and social restrictions have not been developed for small fiber neuropathy (SFN). We developed an SFN‐specific Rasch‐built overall disability scale (SFN‐RODS©), an activity/participation scale at the interval level. A preliminary SFN‐RODS containing 146 activity/participation items was assessed twice (reliability studies) in 238 patients with SFN. The ordinal‐based 13‐item SFN‐symptoms inventory questionnaire (SFN‐SIQ©) and pain‐visual‐analogue‐scale were also assessed (validity studies). The pre‐SFN‐RODS and SFN‐SIQ data were subjected to the Rasch analyses. The pre‐SFN‐RODS did not meet Rasch model expectations. Based on requirements, such as misfit statistics, differential item functioning, and local dependency, items were systematically removed and model fit improved. Finally, a 32‐item SFN‐RODS© scale was constructed that fulfilled all Rasch requirements, demonstrating acceptable reliability and validity scores. The 13‐item SFN‐SIQ© was successfully transformed to an interval Rasch‐built measure fulfilling model's requirements. In conclusion, the 32‐item SFN‐RODS© is a disease‐specific interval measure suitable for detecting activity limitations and participation restrictions in patients with SFN. The 13‐item SFN‐SIQ© was transformed through Rasch to an interval measure. The use of these scales is recommended in future clinical interventional trials involving patients with SFN.     

Rasch analysis of the hospital anxiety and depression scale in Parkinson's disease

The hospital anxiety and depression scale (HADS) is commonly used to assess mood in Parkinson's disease (PD) patients. Very few studies analyze the scale from the standpoint of item response theory. This article sought to analyze how the HADS fits the Rasch model in PD. The HADS was administered to 387 PD patients. Three sets of Rasch analyses were performed for the HADS total score, and anxiety and depression subscales (HADS‐T, ‐A, and ‐D, respectively). Although the HADS‐T and HADS‐A displayed a good fit, with little threshold disordering and no differential item functioning, the HADS‐D failed to fit the model. The person separation index, a reliability measure, was 0.87 (HADS‐T) and 0.80 (HADS‐A). Both HADS‐T and HADS‐A showed unidimensionality. Our results supported the use of HADS‐T as a measure of psychological distress in PD patients. Moreover, the HADS‐A was also an adequate anxiety measure. Further research is required to address the use of HADS‐D in PD. © 2008 Movement Disorder Society     

Is the Parkinson anxiety scale comparable across raters?

The Parkinson Anxiety Scale is a new scale developed to measure anxiety severity in Parkinson's disease specifically. It consists of three dimensions: persistent anxiety, episodic anxiety, and avoidance behavior. This study aimed to assess the measurement properties of the scale while controlling for the rater (self‐ vs. clinician‐rated) effect. The Parkinson Anxiety Scale was administered to a cross‐sectional multicenter international sample of 362 Parkinson's disease patients. Both patients and clinicians rated the patient's anxiety independently. A many‐facet Rasch model design was applied to estimate and remove the rater effect. The following measurement properties were assessed: fit to the Rasch model, unidimensionality, reliability, differential item functioning, item local independency, interrater reliability (self or clinician), and scale targeting. In addition, test–retest stability, construct validity, precision, and diagnostic properties of the Parkinson Anxiety Scale were also analyzed. A good fit to the Rasch model was obtained for Parkinson Anxiety Scale dimensions A and B, after the removal of one item and rescoring of the response scale for certain items, whereas dimension C showed marginal fit. Self versus clinician rating differences were of small magnitude, with patients reporting higher anxiety levels than clinicians. The linear measure for Parkinson Anxiety Scale dimensions A and B showed good convergent construct with other anxiety measures and good diagnostic properties. Parkinson Anxiety Scale modified dimensions A and B provide valid and reliable measures of anxiety in Parkinson's disease that are comparable across raters. Further studies are needed with dimension C. © 2014 International Parkinson and Movement Disorder Society