Advantages of Using Unweighted Approximation Error Measures for Model Fit Assessment.

Fit indices are highly frequently used for assessing the goodness of fit of latent variable models. Most prominent fit indices, such as the root-mean-square error of approximation (RMSEA) or the comparative fit index (CFI), are based on a noncentrality parameter estimate derived from the model fit statistic. While a noncentrality parameter estimate is well suited for quantifying the amount of systematic error, the complex weighting function involved in its calculation makes indices derived from it challenging to interpret. Moreover, noncentrality-parameter-based fit indices yield systematically different values, depending on the indicators' level of measurement. For instance, RMSEA and CFI yield more favorable fit indices for models with categorical as compared to metric variables under otherwise identical conditions. In the present article, approaches for obtaining an approximation discrepancy estimate that is independent from any specific weighting function are considered. From these unweighted approximation error estimates, fit indices analogous to RMSEA and CFI are calculated and their finite sample properties are investigated using simulation studies. The results illustrate that the new fit indices consistently estimate their true value which, in contrast to other fit indices, is the same value for metric and categorical variables. Advantages with respect to interpretability are discussed and cutoff criteria for the new indices are considered.

A note on residual M-distances for identifying aberrant response patterns.

Although a statistical model might fit well to a large proportion of the individuals of a random sample, some individuals might give 'unusual' responses that are not well explained by the hypothesized model. If individual responses are given as continuous response vectors, M-distances can be used to produce real valued indicators of how well an individual's response vector corresponds to a covariance structure implied by a psychometric model. In this note, we focus on the so-called one-factor model. Two M-distances, dsi and dri , which are sensitive to different aspects of the assumed factor model, have been proposed. While one of the M-distances, dri , has been derived based on Bartlett factor scores, in this note we show that the second M-distance, dsi , can be derived in an analogous fashion based on Thomson factor scores.

A Graded Response Model Framework for Questionnaires With Uniform Response Formats.

Questionnaires with uniform-ordered categorical response formats are widely applied in psychology. Muraki proposed a modified graded response model accounting for the items' uniform response formats by assuming identical threshold parameters defining the category boundaries for all items. What is not well known is that there is a set of closely related models, which similarly assume identical thresholds. The present article gives a framework illustrating the differences between these models and their utility for understanding questionnaire responses in detail. The models are explained as constrained cases of a one-dimensional factor model for ordered categorical data. Furthermore, the authors show that the models can be written and fitted as structural equation models, which allows for a very flexible and general purpose use. Instructions on implementing the models in Mplus and SAS PROC NLMIXED are given.

Parallel analysis with categorical variables: Impact of category probability proportions on dimensionality assessment accuracy.

Parallel analysis (PA) is regarded as one of the most accurate methods to determine the number of factors underlying a set of variables. Commonly, PA is performed on the basis of the variables' product-moment correlation matrix. To improve dimensionality assessments for dichotomous or ordered categorical variables, it has been proposed to replace product-moment correlations with more appropriate coefficients, such as tetrachoric or polychoric correlations. While similar modifications have proven useful for various factor analytic approaches, PA results were not consistently improved. The present article outlines a main reason for this result. Specifically, it explains the dependency of PA results on differing proportions of category probabilities when using tetrachoric or polychoric correlations and shows how to adjust for it by generating appropriate reference eigenvalues. The accuracy of dimensionality assessments of PA accounting for category probability proportions versus not accounting for them is investigated using simulation studies. The results show that the category probability adjusted approach distinctly improves dimensionality assessments. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Obstructive sleep apnea patients can be identified by ion mobility spectrometry-derived smell prints of different biological materials.

BACKGROUND: The analysis of obstructive sleep apnoea syndrome (OSAS) is time- and cost-intensive. A number of studies demonstrated that the non-invasive analysis of exhaled breath (EB) may be suitable to distinguish between OSAS patients and healthy subjects (HS). Methods/Population: We included OSAS patients (n = 15) and HS (n = 15) in this diagnostic proof-of-concept-study. All participants underwent polygraphy to verify or exclude OSAS and performed spirometry to exclude pulmonary ventilatory diseases. The volatile organic compound profile of EB and of the headspaces over EB condensate, pharyngeal washing fluid, and serum was measured using ion mobility spectrometry (IMS) (BioScout®) and an e-nose (Cyranose® 320). For the statistical analysis, we fitted classification tree models using recursive partitioning, followed by a leave-one-out cross-validation. For the cross-validated predictions we calculated descriptive classification statistics, p-values from a [Formula: see text]-test with continuity correction, as well as ROC curves. RESULTS: Using IMS, OSAS patients and HS could be distinguished with high accuracy (values ranged from 79% to 97%). The results of the e-nose-derived analyses (with the exception of EB) were less accurate. However, the cross-validated accuracy for EB was very good (0.9), reflecting a positive predictive value of 100% and a negative predictive value of 83%. For each material, we identified the best five substances that may be used for diagnostic purposes. 2-Methylfluran was found in three different biological materials to be discriminative between OSAS and HS. CONCLUSION: The results strengthen the hypothesis that substances detectable in headspace measurements of different airway and blood materials may undergo a transition from blood into the alveoli (and EB) or vice versa. This means that substances from different compartments could be used to distinguish patients with airway diseases (in this case OSAS) from healthy controls.

The Graded Response Differential Discrimination Model Accounting for Extreme Response Style.

Extreme response style or, more generally, individual differences in response spacing have been shown to be an influential bias when analyzing questionnaire data. Recently a promising model adjusting for this bias - the differential discrimination model - has been proposed. An advantage to other related approaches is that the model can be fitted using standard structural equation modeling software. However, the model is designed for analyzing continuous item responses, whereas graded response formats are certainly more prominent in behavioral sciences. To resolve this limitation, the present article extends the differential discrimination model to analyzing graded responses. Empirical examples as well as a small simulation study are presented.

Consistent Differential Discrimination Model Estimation.

A novel factor-analytic model-the differential discrimination model-for assessing individual differences in scale use has been recently introduced, together with a three-stage estimation approach for model fitting. Unfortunately, the second-stage estimator and, as a consequence, the third-stage estimator of this procedure are not consistent. In this article we show that (a) the differential discrimination model can be expressed in a structural equation model framework, and (b) consistent and simultaneous estimation of all model parameters can be achieved using standard SEM software.

Measuring Compounds in Exhaled Air to Detect Alzheimer's Disease and Parkinson's Disease.

BACKGROUND: Alzheimer's disease (AD) is diagnosed based upon medical history, neuropsychiatric examination, cerebrospinal fluid analysis, extensive laboratory analyses and cerebral imaging. Diagnosis is time consuming and labour intensive. Parkinson's disease (PD) is mainly diagnosed on clinical grounds. OBJECTIVE: The primary aim of this study was to differentiate patients suffering from AD, PD and healthy controls by investigating exhaled air with the electronic nose technique. After demonstrating a difference between the three groups the secondary aim was the identification of specific substances responsible for the difference(s) using ion mobility spectroscopy. Thirdly we analysed whether amyloid beta (Aß) in exhaled breath was causative for the observed differences between patients suffering from AD and healthy controls. METHODS: We employed novel pulmonary diagnostic tools (electronic nose device/ion-mobility spectrometry) for the identification of patients with neurodegenerative diseases. Specifically, we analysed breath pattern differences in exhaled air of patients with AD, those with PD and healthy controls using the electronic nose device (eNose). Using ion mobility spectrometry (IMS), we identified the compounds responsible for the observed differences in breath patterns. We applied ELISA technique to measure Aß in exhaled breath condensates. RESULTS: The eNose was able to differentiate between AD, PD and HC correctly. Using IMS, we identified markers that could be used to differentiate healthy controls from patients with AD and PD with an accuracy of 94%. In addition, patients suffering from PD were identified with sensitivity and specificity of 100%. Altogether, 3 AD patients out of 53 participants were misclassified. Although we found Aß in exhaled breath condensate from both AD and healthy controls, no significant differences between groups were detected. CONCLUSION: These data may open a new field in the diagnosis of neurodegenerative disease such as Alzheimer's disease and Parkinson's disease. Further research is required to evaluate the significance of these pulmonary findings with respect to the pathophysiology of neurodegenerative disorders.

Manual versus sonic-powered toothbrushing for plaque reduction in patients with dental implants: an explanatory randomised controlled trial.

PURPOSE: The aim of the present study was to investigate plaque levels following sonic-powered and manual toothbrushing in subjects with dental implants. MATERIALS AND METHODS: This study included 36 male and 47 female partially edentulous patients (age range 45-78 years, mean age 59.8 years) that were randomly assigned to one of two treatment groups: the sonic toothbrush group (n = 42; Philips Sonicare FlexCare® toothbrush) or the manual toothbrush group (n = 41; Oral-B P40®). Clinical, microbiological and immunological examinations were performed blinded at baseline and after 3, 6, 9 and 12 months. Microbiological analyses were performed by real-time polymerase chain reaction. Immunological analyses (prostaglandin E2) were performed by chromatography-electrospray spectrometry. RESULTS: The plaque index difference between baseline and 12 months at implants showed no significant difference between sonic or manual toothbrushing in a two-sided Mann-Whitney test (W = 773.5, P = 0.426, 95% CI -0.64 to 0.20). At the end of the study, there were no significant changes in plaque index, bleeding on probing, gingival index, pocket probing depth, gingival recession, clinical attachment level or the microbiological and immunological outcomes at implants or teeth in either group. CONCLUSIONS: This study uncovered no significant difference between sonic and manual toothbrushing for plaque reduction at implants and teeth. Both toothbrushes maintain healthy peri-implant soft tissue.

Impact of beta blocker medication in patients with platinum sensitive recurrent ovarian cancer-a combined analysis of 2 prospective multicenter trials by the AGO Study Group, NCIC-CTG and EORTC-GCG.

OBJECTIVE: Retrospective analyses suggest that the treatment with beta blocker improves survival in patients with breast cancer and melanoma. The aim of this study was to investigate the impact of medication with beta blocker in patients with recurrent ovarian cancer. METHODS: Included patients received treatment within two prospective clinical trials: AGO-OVAR 2.4 phase I trial (carboplatin/gemcitabine; N=25, protocol AGO-OVAR 2.4) and AGO led intergroup phase III trial (carboplatin vs carboplatin/gemcitabine; N=356, protocol AGO-OVAR 2.5, EORTC-GCG, NCIC CTG). Concurrent medication was documented after every cycle and thorough monitoring was conducted. RESULTS: During the studies 38 patients (9.97%) received a beta blocker as co-medication. Patients treated with beta blockers were significantly older than patients not treated with beta blockers. Response rates to chemotherapy were not different between patients treated with beta blockers and those who were not. After a median follow-up of 17 months, 349 (91.6%) patients had progressive disease and 267 (70.1%) patients had died. No difference in median progression-free survival (7.79 vs 7.62 months (p=0.95)) and overall survival (21.2 vs 17.3 months (p=0.18)) was recorded for patients treated with and without beta blocker. In multivariate analyses including age, platinum free-interval, study treatment and ECOG performance status beta blocker treatment was not associated with a significant impact on progression-free survival (HR: 0.92; 95% CI: 0.65-1.31; p=0.65) and overall survival (HR:0.74; 95%CI: 0.49-1.11; p=0.15). CONCLUSIONS: In this series of recurrent platinum-sensitive ovarian cancer patients it could not be confirmed whether beta blocker treatment was associated with better or worse outcome.

Total versus near-total thyroidectomy in Graves' disease and their outcome on postoperative transient hypoparathyroidism: study protocol for a randomized controlled trial?

BACKGROUND: Graves' disease is an independent risk factor for transient postoperative hypoparathyroidism. Besides the disease itself, preparation techniques are influential. Transient postoperative hypoparathyroidism has severe consequences for patients' physical and psychological state. It can be life threatening during the acute phase and may impair patients' health, psyche and quality of life thereafter. For the surgical therapy of Graves' disease, total thyroidectomy is recommended according to the national S2-guideline. The evidence- based on a metaanalysis- is criticized by the Cochrane diagnostic review commentary for substantial methodological deficits. Two randomized controlled trials lead to the hypothesis that a near-total resection with bilateral remnants of ≤ 1g on each side compared to total thyroidectomy will significantly reduce the occurrence of transient postoperative hypoparathyroidism with equal therapeutic safety. METHODS/DESIGN: Patients with Graves' disease indicated for definite surgery are eligible for the trial. Trial-specific exclusion criteria are: conservative treatment, malignancy, previous thyroid surgery and coincident hypoparathyroidism. The trial is created for therapeutic purpose through process innovation. It is designed as a prospective randomized controlled patient and observer blinded multicentered trial in a parallel design including an active comparator and an intervention group. The intervention addresses the surgical procedure: near-total thyroidectomy leaving bilateral remnants of ≤ 1g on each side in the intervention group and total thyroidectomy in the control group. The occurrence of transient postoperative hypoparathyroidism is defined as primary endpoint. Secondary endpoints are: reoperations due to bleeding, recurrent laryngeal nerve palsy, permanent hypoparathyroidism, recurrent disease, changes of endocrine orbitopathy and quality of life within a one-year follow-up period. The primary efficacy analysis follows the intention-to-treat principle. A binary logistic regression model will be applied. Complications and serious adverse events will be descriptively analyzed. DISCUSSION: The trail is expected to balance out the shortcomings of the current evidence. It will define the surgical gold standard for the surgical therapy of Graves' disease. Patients' safety and quality of life are assumed to be enhanced. Therapy costs are likely to be reduced and health care optimized. The conduction of the trial is feasible through the engagement and commitment of the German association of endocrine surgeons and the National Network for Surgical Trials. TRIAL REGISTRATION: German clinical trials register (DRKS) DRKS00004161.

[Psychological distress of breast cancer patients: screening and patients' request for psycho-oncological care as indicators of health-related quality of life]. / Psychische Belastung von Brustkrebspatientinnen: Screening und psychoonkologischer Unterstützungswunsch als Indikatoren der Lebensqualität.

Health-related quality of life (QoL) in breast cancer patients strongly depends on emotional well-being. QoL (EORTC-QLQ-C30), psychological distress (HADS), and patient's request for psycho-oncological care were assessed in 103 breast cancer patients during initial hospitalization. Clinical diagnoses according to ICD-10-F were made by clinical interview. As expected, both positive HADS screens (>13) and clinical diagnoses of mental disorders were inversely related to QoL. However, in multivariate analysis of variance only positive HADS scores but not clinical diagnoses of mental disorders significantly predicted QoL. The performance of psychological screening instruments should therefore not only be judged by their ability to detect clinical diagnoses but also by their relevance for reflecting patients' QoL.