Unidimensional Measurement Research Articles

Application of Rasch Analysis in Developing Sport Event Service Quality Scale

The main purpose of this study was to apply the Rasch model to student athletes perceived event service quality scale and to construct the interval and objective measurement model for the scale. Total three hundred and seventy-seven valid questionnaires were collected from the student athletes of 2010 National Intercollegiate Athletic Games. The results indicated that the scale can treat as uni-dimensional measurement for overall student perceived event service quality. A modified 4-point rating scale was found more suitable than original 5-point scale to Rasch model analysis. The global model fit and person fit were found to be acceptable with the empirical data. Item fit analysis showed that 4 misfit items need to be eliminated from the scale. With the determined 34- item scale, the Rasch model was utilized to estimate item difficulties and participant perceived scores. The most difficult items of the scale were observed from the ”Environment and Facility” factor and the easiest were found from the ”Accomplishment and Experience” factor. Furthermore, the items’ difficulties were invariant by gender. The differences of estimated scores were found not significant by gender, compete level and participate frequency for student athletes perceived service quality about the Intercollegiate Athlete Games. However, gymnastic athletes showed a significant higher score than swimming athletes. This study concludes that the data obtained with student athlete perceived event service quality scale from the National Intercollegiate Athletic Games fit with the Rasch model, which means Rasch model is able to meet the purpose to have interval and objective measure. It could be used for related studies in future.

Target lesion selection as a source of variability of response classification by RECIST 1.1.

11077 Background: Response classification in RECIST is based on manual uni-dimensional quantification of changes of target lesion size. In RECIST 1.1, the maximum number of target lesions was reduced to 5, with a maximum of 2 per organ. We analyzed the importance of different factors (manual vs. automated size measurement, uni- vs. three-dimensional size assessment, and between-reader-variability of target lesion selection) on response categorization. Methods: 41 female patients (58.1±13.2 y) with metastatic breast cancer underwent contrast-enhanced thoraco-abdominal CT for initial staging and first follow-up after systemic chemotherapy. Data were independently and prospectively interpreted by three radiologists. In addition, response was evaluated by a CAD system that allowed automated uni- and three-dimensional assessment of target lesions. Results: Response classification differed between readers in 19/41 patients (46%). In 25/41 patients, readers chose the same target lesions. In 6 of these 25 patients (24%), readers disagreed with regards to response classification. In 16/41 patients, readers chose different target lesions. In 13 of these 16 patients, readers disagreed (81%) (p < 0.001). When dichotomizing response classification according to its therapeutic implication into progressive vs. non-progressive disease, readers disagreed in 11/41 patients (27%). In 9 of these 11 patients, readers had chosen different target lesions. Classification by manual vs. automated uni-dimensional measurement differed in 11/41 of patients (27%). Classification by uni-dimensional vs. volumetric measurements differed in 6/41 of patients (15%). Conclusions: Response classification by RECIST suffers from substantial between-reader variability. Major source of variability is not the manual or uni-dimensional measurement, but the variable choice of target lesions between readers. [Table: see text]

Exploring intra- and inter-reader variability in uni-dimensional, bi-dimensional, and volumetric measurements of solid tumors on CT scans reconstructed at different slice intervals

ObjectiveUnderstanding magnitudes of variability when measuring tumor size may be valuable in improving detection of tumor change and thus evaluating tumor response to therapy in clinical trials and care. Our study explored intra- and inter-reader variability of tumor uni-dimensional (1D), bi-dimensional (2D), and volumetric (VOL) measurements using manual and computer-aided methods (CAM) on CT scans reconstructed at different slice intervals. Materials and methodsRaw CT data from 30 patients enrolled in oncology clinical trials was reconstructed at 5, 2.5, and 1.25mm slice intervals. 118 lesions in the lungs, liver, and lymph nodes were analyzed. For each lesion, two independent radiologists manually and, separately, using computer software, measured the maximum diameter (1D), maximum perpendicular diameter, and volume (CAM only). One of them blindly repeated the measurements. Intra- and inter-reader variability for the manual method and CAM were analyzed using linear mixed-effects models and Bland–Altman method. ResultsFor the three slice intervals, the maximum coefficients of variation for manual intra-/inter-reader variability were 6.9%/9.0% (1D) and 12.3%/18.0% (2D), and for CAM were 5.4%/9.3% (1D), 11.3%/18.8% (2D) and 9.3%/18.0% (VOL). Maximal 95% reference ranges for the percentage difference in intra-reader measurements for manual 1D and 2D, and CAM VOL were (−15.5%, 25.8%), (−27.1%, 51.6%), and (−22.3%, 33.6%), respectively. ConclusionsVariability in measuring the diameter and volume of solid tumors, manually and by CAM, is affected by CT slice interval. The 2.5mm slice interval provides the least measurement variability. Among the three techniques, 2D has the greatest measurement variability compared to 1D and 3D.

Assessing the Validity of the Dynamic Gait Index in a Balance Disorders Clinic: An Application of Rasch Analysis

The Dynamic Gait Index (DGI) has emerged as a valid indicator of functional gait abilities for people with balance and vestibular disorders. Recent Rasch-based analyses have indicated possible concerns for multidimensionality and a ceiling effect within the DGI. The aim of this study was to evaluate the DGI in a sample of patients from a dizziness and balance clinic to determine whether patient features such as dizziness or fall history influence the measurement characteristics of the DGI. This study used a retrospective design. A sample of 117 patients' charts was reviewed, and patients were grouped according to a primary impairment of dizziness only or imbalance and were categorized based on a history of falls. A one-parameter Rasch-Andrich rating scale model was used with thorough analyses, including rating scale analysis, item-difficulty hierarchy, scale unidimensionality, and differential item functioning (DIF). The DGI demonstrated an effective rating scale design and was found to be a unidimensional measurement of dynamic gait. The DGI displayed a modest ceiling effect, primarily with patients with higher functional levels displaying symptoms of dizziness. Three items ("vertical head nods," "gait on level surface," and "stepping over obstacles") demonstrated DIF based on categories of patient characteristics, although the effects on measurement were negligible. Functional categories were based on impairments and not underlying medical diagnoses derived from a retrospective chart review, whereas the limited sample size may have underestimated statistically significant DIF. Results from this study offer additional evidence supporting the validity of the DGI as a measure of gait ability. The present findings also are in agreement with prior research that has shown a ceiling effect for the DGI in people with balance or vestibular disorders. Effects of DIF were found to be negligible, yet the presence of DIF within the present sample helped to explain some differences in DGI item-difficulty hierarchies from prior studies. Continued research is needed to determine how population differences may affect performance on the DGI and to develop and test assessments capable of measuring a broader range of gait abilities.

Measuring engagement in deliberate self-harm behaviours: psychometric evaluation of six scales

BackgroundEngagement in Deliberate Self-Harm (DSH) is commonly measured by behavioural scales comprised of specific methods of self-harm. However, there is a scarcity of information about the degree to which the methods relate to the same DSH construct although such scales are routinely used to provide a DSH total score. This study addresses the shortfall by evaluating the dimensionality of six commonly used behavioural measures of DSH.MethodsThe DSH measures were Self-Injury Questionnaire Treatment Related (SIQTR), Self-Injurious Thoughts and Behaviors Interview (SITBI), Deliberate Self-Harm Inventory (DSHI), Inventory of Statements About Self-Injury (ISAS), Self-Harm Information Form (SHIF) and Self-Harm Inventory (SHI). The behavioural scales contained in each measure were administered to 568 young Australians aged 18 to 30 years (62% university students, 21% mental health patients, and 17% community members). Scale quality was examined against the stringent standards for unidimensional measurement provided by the Rasch model.ResultsAccording to the stringent post-hoc tests provided by the Rasch measurement model, there is support for the unidimensionality of the items contained within each of the scales. All six scales contained items with differential item functioning, four scales contained items with local response dependency, and one item was grossly misfitting (due to a lack of discrimination).ConclusionsThis study supports the use of behavioural scales to measure a DSH construct, justifies the summing of items to form a total DSH score, informs the hierarchy of DSH methods in each scale, and extends the previous evidence for reliability and external validity (as provided by test developers) to a more complete account of scale quality. Given the overall adequacy of all six scales, clinicians and researchers are recommended to select the scale that best matches their adopted definition of DSH.

Laser Doppler anemometry measurements of steady flow through two bi-leaflet prosthetic heart valves

IntroductionIn vitro hydrodynamic characterization of prosthetic heart valves provides important information regarding their operation, especially if performed by noninvasive techniques of anemometry. Once velocity profiles for each valve are provided, it is possible to compare them in terms of hydrodynamic performance. In this first experimental study using laser doppler anemometry with mechanical valves, the simulations were performed at a steady flow workbench.Objective To compare unidimensional velocity profiles at the central plane of two bi-leaflet aortic prosthesis from St. Jude (AGN 21 - 751 and 21 AJ - 501 models) exposed to a steady flow regime, on four distinct sections, three downstream and one upstream. MethodsTo provide similar conditions for the flow through each prosthesis by a steady flow workbench (water, flow rate of 17L/min. ) and, for the same sections and sweeps, to obtain the velocity profiles of each heart valve by unidimensional measurements. ResultsIt was found that higher velocities correspond to the prosthesis with smaller inner diameter and instabilities of flow are larger as the section of interest is closer to the valve. Regions of recirculation, stagnation of flow, low pressure, and flow peak velocities were also found. Conclusions Considering the hydrodynamic aspect and for every section measured, it could be concluded that the prosthesis model AGN 21 - 751 (RegentTM) is superior to the 21 AJ - 501 model (Master Series). Based on the results, future studies can choose to focus on specific regions of the these valves.

Логические и практические трудности многомерного подхода к измерению религиозности

The article is dedicated to analysis of difficulties arising from applying multidimensional approach to religiosity. Those difficulties are divided into logical and practical ones. Logical difficulties are connected with the absence of clear base (self-evident, theoretical or empirical) prescribing the usage of one set of scales or another and the framework of such usage. Practical difficulties are explained in context of social research practice where multidimensional scaling of religiosity is eventually non-applicable nowadays. Conclusion made regards the advantage of unidimensional measurement.

Examining Quality of Mathemtics Test Items Using Rasch Model: Preminarily Analysis

Producing a high quality of test items needs a substantial time and efforts in developing and examining each test item. Literature suggested this limitation can be remedied with a large collection of test items along with their measurement characteristics which termed as item bank. However, a well-developed item bank is formed by a set of high quality of test items using a rigorous development and validation procedures. In achieving this, this study attempts to describe the development of Malaysian secondary school Form two Mathematics item bank; and to examine the psychometric properties of the test items which developed based on Malaysian Mathematics Curriculum Specifications. The sample consisted of 1 316 Form two students selected from 12 secondary schools in the state of Penang and Perak. Data was analyzed using Rasch Unidimensional Measurement Model with WinSteps computer program. The results showed that 19 out of 160 items were excluded as not fitting Rasch measurement model. Thus, only 141 items were stored in the item bank and empirically fulfilled the quality as suggested by the Rasch measurement model. This study contributes to create Malaysian Mathematics item bank which deserves to be further created, tested and modified the computer adaptive testing (CAT) program.

Cardiac Depression Scale: Mokken scaling in heart failure patients

BackgroundThere is a high prevalence of depression in patients with heart failure (HF) that is associated with worsening prognosis. The value of using a reliable and valid instrument to measure depression in this population is therefore essential. We validated the Cardiac Depression Scale (CDS) in heart failure patients using a model of ordinal unidimensional measurement known as Mokken scaling.FindingsWe administered in face-to-face interviews the CDS to 603 patients with HF. Data were analysed using Mokken scale analysis. Items of the CDS formed a statistically significant unidimensional Mokken scale of low strength (H<0.40) and high reliability (Rho>0.8).ConclusionsThe CDS has a hierarchy of items which can be interpreted in terms of the increasingly serious effects of depression occurring as a result of HF. Identifying an appropriate instrument to measure depression in patients with HF allows for early identification and better medical management.

Tumor Volume as an Alternative Response Measurement for Imatinib Treated GIST Patients

BackgroundAssessment of tumor size changes is crucial in clinical trials and patient care. We compared imatinib-induced volume changes of liver metastases (LM) from gastro-intestinal stromal tumors (GIST) to RECIST and Choi criteria and their association with overall survival (OS).MethodsLM from 84 GIST patients (training and validation set) were evaluated using manual and semi-automated Computed Tomography measurements at baseline, after 3, 6 and 12 months of imatinib. The ability of uni-dimensional (1D) and three-dimensional (3D) measurements to detect size changes (increase/decrease) ≥20% was evaluated. Volumetric response cut-offs were derived from minimally relevant changes (+20/−30%) by RECIST, considering lesions as spherical or ellipsoidal.Results3D measurements detected size changes ≥20% more frequently than 1D at every time-point (P≤0.008). 3D and Choi criteria registered more responses than RECIST at 3 and 6 months for 3D-spheres (P≤0.03) and at all time-points for 3D-ellipsoids and Choi criteria (P<0.001). Progressive disease by 3D criteria seems to better correlate to OS at late time-points than other criteria.ConclusionVolume criteria (especially ellipsoids) classify a higher number of patients as imatinib-responders than RECIST. Volume discriminates size changes better than diameter in GIST and constitutes a feasible and robust method to evaluate response and predict patient benefit.

Scoring and Modeling Psychological Measures in the Presence of Multidimensionality

Confirmatory factor analytic studies of psychological measures showing item responses to be multidimensional do not provide sufficient guidance for applied work. Demonstrating that item response data are multifactorial in this way does not necessarily (a) mean that a total scale score is an inadequate indicator of the intended construct, (b) demand creating and scoring subscales, or (c) require specifying a multidimensional measurement model in research using structural equation modeling (SEM). To better inform these important decisions, more fine-grained psychometric analyses are necessary. We describe 3 established, but seldom used, psychometric approaches that address 4 distinct questions: (a) To what degree do total scale scores reflect reliable variation on a single construct? (b) Is the scoring and reporting of subscale scores justified? (c) If justified, how much reliable variance do subscale scores provide after controlling for a general factor? and (d) Can multidimensional item response data be represented by a unidimensional measurement model in SEM, or are multidimensional measurement models (e.g., second-order, bifactor) necessary to achieve unbiased structural coefficients? In the discussion, we provide guidance for applied researchers on how best to interpret the results from applying these methods and review their limitations.

Psychometric properties of the Chinese versions of the Quick Inventory of Depressive Symptomatology – Clinician Rating (C-QIDS-C) and Self-Report (C-QIDS-SR)

BackgroundDeveloping accurate and time-efficient tools to measure depressive symptoms is important for research and clinical practice. This study aimed to test the psychometric properties of the Chinese version of the 16-item Quick Inventory of Depressive Symptomatology – Clinician Rating (C-QIDS-C) and Self-Report (C-QIDS-SR). MethodsThis study included 998 patients with major depressive disorder (MDD) established using the Mini International Neuropsychiatric Interview (MINI). The severity of depressive symptoms was assessed using the Hamilton Rating Scale for Depression (HAMD), C-QIDS-C and C-QIDS-SR at baseline and 6 weeks later. ResultsInternal consistency (Cronbach’s alpha) ranged from 0.73 to 0.82 for C-QIDS-C and C-QIDS-SR at both the baseline and exit. The involvement and energy domains at baseline, and sad mood, concentration/decision making, self outlook, involvement and agitation/retardation domains at exit had the highest item-total correlations across the two C-QIDS scales. The C-QIDS-C and C-QIDS-SR total scores were highly correlated with the HAMD total score at both baseline (r=0.61, p<0.01 and r=0.54, p<0.01, respectively) and exit (r=0.75, p<0.01 and r=0.72, p<0.01, respectively). The C-QIDS-C, C-QIDS-SR and HAMD were equally sensitive to change of depressive symptoms, suggesting high concurrent validity. The C-QIDS-C and C-QIDS-SR showed uni-dimensional measurement properties in exploratory factor analyses at both baseline and exit. ConclusionsThe C-QIDS-C and C-QIDS-SR have excellent psychometric properties and are sensitive measurement of symptom severity in MDD.

The configuration of power in vertical relationships in the food supply chain in the Canary Islands

PurposeToday's environment imposes traceability compliance on food firms. Power within the interorganisational relationships in the food supply chain may hinder the integration necessary for that traceability to be effective. The purpose of the present study is to define the configuration of power in food industry‐distribution relationships from the food industry perspective.Design/methodology/approachThe variables of power configuration considered in this study have been classified as mediated and non‐mediated power sources, in accordance with the criteria used by French and Raven. The Rasch model employed in the treatment of the values given by the food industries to the construct perceived power (mediated and non‐mediated power sources) permit a unidimensional measurement of that construct. Thus, the model estimated using this methodology explains power‐shaping in the food industry‐distribution relationships in the Canary Islands.FindingsThe results obtained are mostly based on the distributors' use of mediated power sources; they describe a situation that does not contribute to a high level of commitment in such relationships, since the negative effects of this type of power do not favour the climate required for the implementation of active traceability.Research limitations/implicationsThe data applied in this study were gathered prior to the implementation of traceability as a legal requirement, and consequently it would be advisable and useful to conduct a post‐implementation.Originality/valueThe paper adopts a business management approach, aimed at improving relations in the food supply chain. The methodology employed allows food firms to establish suitable chain integration strategies, facilitating the effective implementation of traceability. The paper presents a conceptual framework and analytical methodology which sustain the present study and subsequent work.

Multidimensionality and Structural Coefficient Bias in Structural Equation Modeling

In this study, the authors consider several indices to indicate whether multidimensional data are “unidimensional enough” to fit with a unidimensional measurement model, especially when the goal is to avoid excessive bias in structural parameter estimates. They examine two factor strength indices (the explained common variance and omega hierarchical) and several model fit indices (root mean square error of approximation, comparative fit index, and standardized root mean square residual). These statistics are compared in population correlation matrices determined by known bifactor structures that vary on the (a) relative strength of general and group factor loadings, (b) number of group factors, and (c) number of items or indicators. When fit with a unidimensional measurement model, the degree of structural coefficient bias depends strongly and inversely on explained common variance, but its effects are moderated by the percentage of correlations uncontaminated by multidimensionality, a statistic that rises combinatorially with the number of group factors. When the percentage of uncontaminated correlations is high, structural coefficients are relatively unbiased even when general factor strength is low relative to group factor strength. On the other hand, popular structural equation modeling fit indices such as comparative fit index or standardized root mean square residual routinely reject unidimensional measurement models even in contexts in which the structural coefficient bias is low. In general, such statistics cannot be used to predict the magnitude of structural coefficient bias.

MRI volume measurements compared with the RECIST 1.1 for evaluating the response to neoadjuvant chemotherapy for mass-type lesions

The purpose of this study was to compare the accuracy of volumetric (3D) measurements with that of unidimensional (1D) measurements by response evaluation criteria in solid tumors 1.1 (RECIST 1.1) in patients with breast cancer before and after neoadjuvant chemotherapy. The study included 48 patients with breast cancer who underwent neoadjuvant chemotherapy. Dynamic contrast-enhanced magnetic resonance imaging was performed before the first cycle of chemotherapy and after the completion of the planned chemotherapy. The longest diameter and volume of each target lesion were measured using a TeraRecon Aquarius workstation (San Mateo, CA). Response was assessed both by using the RECIST 1.1 and volumetric criteria. Histologic response was assessed using the Sataloff criteria. The agreements between the two measures and the histologic response were analyzed statistically. In monitoring the response to neoadjuvant chemotherapy, the 1D and 3D measurements showed "good agreement" (κ=0.610) for the treatment response categories and "moderate agreement" (κ=0.565) for the responder/non-responder categories. Disagreement was observed in 9 out of 48 comparisons (18.75%). The percent agreement of the 1D measurement of residual lesions (79.17%) with the pathology was higher than that by volumetric measurement (70.83%), but there was no statistically significant difference (p=0.35). Both the 1D (rho=0.67, p<0.0001) and 3D measurements (rho=0.52, p<0.0001) showed a moderate degree of linear correlation with the pathologic diameter of residual lesions. There was generally good agreement between the 1D and 3D measurements and moderate predictive value using either approach for predicting pathological response.

The Measurement of Entrepreneurial Orientation

This article explores how the concept of entrepreneurial orientation (EO) has been portrayed and assessed in prior research. The challenges and decision criteria associated with formative versus reflective measurement approaches are reviewed. It is argued that, as a latent construct, EO exists apart from its measures and that researchers are free to choose whichever measurement approach best serves their research purposes, recognizing that unidimensional versus multidimensional EO measurement models are consistent with fundamentally different conceptualizations of the EO construct. Recommendations are offered regarding potentially appropriate formative and reflective measures of EO.

Scale construction utilising the Rasch unidimensional measurement model: A measurement of adolescent attitudes towards abortion

Measurement scales seeking to quantify latent traits like attitudes, are often developed using traditional psychometric approaches. Application of the Rasch unidimensional measurement model may complement or replace these techniques, as the model can be used to construct scales and check their psychometric properties. If data fit the model, then a scale with invariant measurement properties, including interval-level scores, will have been developed. This paper highlights the unique properties of the Rasch model. Items developed to measure adolescent attitudes towards abortion are used to exemplify the process. Ten attitude and intention items relating to abortion were answered by 406 adolescents aged 12 to 19 years, as part of the "Teen Relationships Study". The sampling framework captured a range of sexual and pregnancy experiences. Items were assessed for fit to the Rasch model including checks for Differential Item Functioning (DIF) by gender, sexual experience or pregnancy experience. Rasch analysis of the original dataset initially demonstrated that some items did not fit the model. Rescoring of one item (B5) and removal of another (L31) resulted in fit, as shown by a non-significant item-trait interaction total chi-square and a mean log residual fit statistic for items of -0.05 (SD=1.43). No DIF existed for the revised scale. However, items did not distinguish as well amongst persons with the most intense attitudes as they did for other persons. A person separation index of 0.82 indicated good reliability. Application of the Rasch model produced a valid and reliable scale measuring adolescent attitudes towards abortion, with stable measurement properties. The Rasch process provided an extensive range of diagnostic information concerning item and person fit, enabling changes to be made to scale items. This example shows the value of the Rasch model in developing scales for both social science and health disciplines.

Single-dimension CT measurements with RECIST 1.1 to evaluate liver metastases in GIST patients on imatinib.

10091 Background: Tumor response assessment to therapy is crucial in oncology, both in daily practice and research.We analyzed the morphology of liver metastases (LM) in gastrointestinal stromal tumors (GIST). Aims were to 1) determine whether uni-dimensional measurements of tumor lesions (according to RECIST 1.1) are accurate reflections of their volumes and 2) estimate eventual bias in volume change calculations, as introduced by using only the longest diameter. Methods: 78 GIST patients with LM were evaluated at baseline (n=139 lesions), 3 (n=129), 6 (n=128), and 12 months (n=108) after imatinib therapy. LM were segmented semi-automatically on standard CT scans. All measurements at baseline were obtained by 2 independent investigators and agreement between observers was assessed with Bland-Altman plots. Values for segmented volume (Vs; mL), maximum transaxial diameter (MTD; mm), and elongation value (EV, defined as 1 - [width/length], where EV of 1 = fully ellipsoidal and 0 = fully spherical) were reported for each lesion at several time-points. A calculated volume (Vc) of each LM was also generated using the MTD, with the hypothesis that metastases were fully spherical. Results: At baseline, 44% (61/139) of the LM was spherical and 56% (78/139) was ellipsoidal. Their EV ranged from 0.08 to 0.94 (mean, 0.53±0.17). During treatment, overall 42% of the lesions kept their morphology (spherical or ellipsoidal) and the other half changed from spherical to ellipsoidal or vice versa. At baseline, there was strong inter-observer agreement in the determination of Vs, with mean inter-observer variability of 1.5% (95% CI, -14.5% to 17.5%). The difference between Vs and Vc was highly significant (P&lt;0.0001). Vc overestimates the actual volume of 35% (95% CI, -26% to 95%). Conclusions: LM are not always spherical and can change their morphology during imatinib therapy. Therefore, a lesion's single largest trans-axial dimension, as used in RECIST 1.1, is not an accurate surrogate of its actual volume. Further studies are warranted to fully understand the clinical impact of these findings and to assess whether we should apply different criteria for response assessment to therapies in solid tumors.

Distinguishing symptom dimensions of depression and anxiety: An integrative approach

Clark and Watson developed the tripartite model in which a symptom dimension of 'negative affect' covers common psychological distress that is typically seen in anxious and depressed patients. The 'positive affect' and 'somatic arousal' dimensions cover more specific symptoms. Although the model has met much support, it does not cover all relevant anxiety symptoms and its negative affect dimension is rather unspecific. Therefore, we aimed to extend the tripartite model in order to describe more specific symptom patterns with unidimensional measurement scales. 1333 outpatients provided self report data. To develop an extended factor model, exploratory factor analysis (EFA) was conducted in one part of the data (n=578). Confirmatory factor analysis (CFA) was conducted in the second part (n=755), to assess model-fit and comparison with other models. Rasch analyses were done to investigate the unidimensionality of the factors. EFA resulted in a 6-factor model: feelings of worthlessness, fatigue, somatic arousal, anxious apprehension, phobic fear and tension. CFA in the second sample showed that a 6-factor model with a hierarchical common severity factor fits the data better than alternative 1- and 3-factor models. Rasch analyses showed that each of the factors and the total of factors can be regarded as unidimensional measurement scales. The model is based on a restricted symptom-pool: more dimensions are likely to exist. The extended tripartite model describes the clinical state of patients more specifically. This is relevant for both clinical practice and research.

Assessing the effect of CT slice interval on unidimensional, bidimensional and volumetric measurements of solid tumours

Objectives: To study the magnitude of differences in tumour unidimensional (1D), bidimensional (2D) and volumetric (VOL) measurements determined from computed tomography (CT) images reconstructed at 5, 2.5 and 1.25 mm slice intervals. Materials and Methods: A total of 118 lesions in lung, liver and lymph nodes were selected from 30 patients enrolled in early phase clinical trials. Each CT scan was reconstructed at 5, 2.5 and 1.25 mm slice intervals during the image acquisition. Lesions were semi-automatically segmented on each interval image series and supervised by a radiologist. 1D, 2D and VOL were computed based on the final segmentation results. Average measurement differences across different slice intervals were obtained using linear mixed-effects analysis of variance models. Results: Lesion diameters ranged from 6.1 to 80.1 mm (median 18.4 mm). The largest difference was seen between 1.25 and 5 mm (mean difference of 7.6% for 1D [P < 0.0001], 13.1% for 2D [P < 0.0001], −5.7% for VOL [P = 0.0001]). Mean differences between 1.25 and 2.5 mm were all within ±3.5% (within ±6% confidence interval). For VOL, there was a larger average difference between measurements on different slice intervals for the smaller lesions (<10 mm) compared with the larger lesions. Conclusions: Different slice intervals may give different 1D, 2D and VOL measurements. In clinical practice, it would be prudent to use the same slice interval for consecutive measurements.