Linear mixed-effects models for the analysis of high-density electromyography with application to diabetic peripheral neuropathy.

This article demonstrates the power and flexibility of linear mixed-effects models (LMEMs) to investigate high-density surface electromyography (HD-sEMG) signals. The potentiality of the model is illustrated by investigating the root mean squared value of HD-sEMG signals in the tibialis anterior muscle of healthy (n = 11) and individuals with diabetic peripheral neuropathy (n = 12). We started by presenting the limitations of traditional approaches by building a linear model with only fixed effects. Then, we showed how the model adequacy could be increased by including random effects, as well as by adding alternative correlation structures. The models were compared with the Akaike information criterion and the Bayesian information criterion, as well as the likelihood ratio test. The results showed that the inclusion of the random effects of intercept and slope, along with an autoregressive moving average correlation structure, is the one that best describes the data (p < 0.01). Furthermore, we demonstrate how the inclusion of additional variance structures can accommodate heterogeneity in the residual analysis and therefore increase model adequacy (p < 0.01). Thus, in conclusion, we suggest that adopting LMEM to repeated measures such as electromyography can provide additional information from the data (e.g. test for alternative correlation structures of the RMS value), and hence provide new insights into HD-sEMG-related work.

An aircraft seat discomfort scale using item response theory.

The purpose of this study is to construct an aircraft seat discomfort scale and verify the evidence of its validity and reliability. We developed a questionnaire and presented it to 1500 Brazilian passengers at an airport. The data analysis included: 1) factor analysis; 2) the analysis of the items to be used in the scale created using Item Response Theory. The scale covered all levels, from "without discomfort" to "maximum discomfort". At the level of minimal, a passenger feels that the aircraft seat is cramped and has little space. Discomfort tends to increase when passengers are unable to perform desired activities (eg: reading, sleeping), which causes irritation and disappointment. The maximum discomfort level occurs when noise disrupts activities and an aircraft seat is considered hard. The scale developed presented indications that it is reliable and valid, proving to be a useful tool for identifying levels of discomfort in aircraft seats.

Shift work and sex are variants across Karolinska Sleep Questionnaire and the application of linking analysis as a step forward using Item Response Theory.

The frequency of sleep disturbances is considerably higher in the night and shift workers and in females than in day workers and males, respectively. However, a subjective sleep scale must be invariant across these groups, independently of the level of their members on the scale. This study is aimed to test the invariance of the Karolinska Sleep Questionnaire's (KSQ) items by shift work and sex. We used the data from a census that covered more than 90% (N = 1648) of the nurses from the main institute of the largest public hospital complex of Brazil. Firstly, we intend to find the KSQ's dimensionality using factorial analysis and Item Response Theory (IRT) performed by Graded Response Model. Differential Item Functioning (DIF) was the technique used to test the invariance of each KSQ's dimensions. In case of variance detection, we applied the linking analysis. Intending to test the KSQ's consistency with external variables, we assessed correlations between KSQ's dimensions with health variables, i.e., self-reported health status and musculoskeletal pain. We have found one scale and two subscales from one general and another bidimensional factor structure of the KSQ, respectively. In these dimensions, the KSQ's items fitted well to the IRT and we have identified DIF by shift work. However, we have found DIF by sex just in one item on the general factor. Linking analysis showed as a possible step forward in the variance issue placing on to the same scale the shift work groups in the items with DIF. All correlations between KSQ's dimensions with health variables were significant. Our findings allow us to argue that KQS's items were variant by shift work and sex in a nursing staff census from the largest public hospital complex of Brazil, but we can go on using linking analysis. This could be used as an evidence for the construct validity should go beyond the traditional dimensionality assessment. The dimensionalities of KSQ fit well for other population but individuals living in Scandinavian countries.

Instrument for Assessing Knowledge of Oral Anticoagulant Therapy: Construction and Validation.

BACKGROUND AND PURPOSE: A valid and reliable assessment tool is fundamental for evaluating the knowledge of individuals about using oral anticoagulant therapy (OAT). The purpose of this study was to develop a tool to assess knowledge about OAT and provide evidence to support its use in people living in developing countries. METHODS: Construction and validation: development of items; assessment of face and content validity; pilot study; application of the instrument to a sample of 500 users of OAT to analyze dimensionality, convergent validation, and reliability. RESULTS: Analysis of dimensionality suggested a unidimensional instrument. Direct correlation between knowledge of OAT and educational level was confirmed (r = .61, p < .001) (validity of construct). Reliability measured by KR-20 was 0.86. CONCLUSIONS: The new instrument was shown to be valid and reliable for assessing knowledge of OAT in the population studied.

Measuring the quality of life in hypertension according to Item Response Theory.

OBJECTIVE: To analyze the Miniquestionário de Qualidade de Vida em Hipertensão Arterial (MINICHAL - Mini-questionnaire of Quality of Life in Hypertension) using the Item Response Theory. METHODS: This is an analytical study conducted with 712 persons with hypertension treated in thirteen primary health care units of Fortaleza, State of Ceará, Brazil, in 2015. The steps of the analysis by the Item Response Theory were: evaluation of dimensionality, estimation of parameters of items, and construction of scale. The study of dimensionality was carried out on the polychoric correlation matrix and confirmatory factor analysis. To estimate the item parameters, we used the Gradual Response Model of Samejima. The analyses were conducted using the free software R with the aid of psych and mirt. RESULTS: The analysis has allowed the visualization of item parameters and their individual contributions in the measurement of the latent trait, generating more information and allowing the construction of a scale with an interpretative model that demonstrates the evolution of the worsening of the quality of life in five levels. Regarding the item parameters, the items related to the somatic state have had a good performance, as they have presented better power to discriminate individuals with worse quality of life. The items related to mental state have been those which contributed with less psychometric data in the MINICHAL. CONCLUSIONS: We conclude that the instrument is suitable for the identification of the worsening of the quality of life in hypertension. The analysis of the MINICHAL using the Item Response Theory has allowed us to identify new sides of this instrument that have not yet been addressed in previous studies. OBJETIVO: Analisar o Miniquestionário de Qualidade de Vida em Hipertensão Arterial (MINICHAL) por meio da Teoria da Resposta ao Item. MÉTODOS: Estudo analítico realizado com 712 pessoas com hipertensão arterial atendidas em 13 unidades de atenção primária em saúde de Fortaleza, CE, em 2015. As etapas da análise pela Teoria da Resposta ao Item foram: avaliação da dimensionalidade, estimação dos parâmetros dos itens e construção da escala. O estudo da dimensionalidade foi realizado sobre a matriz de correlação policórica e análise fatorial confirmatória. Para a estimação dos parâmetros dos itens, foi utilizado o Modelo de Resposta Gradual de Samejima. As análises foram conduzidas no software livre R com o auxílio dos pacotes psych e mirt. RESULTADOS: A análise permitiu a visualização dos parâmetros dos itens e suas contribuições individuais na mensuração do traço latente, gerando mais informação, permitindo a construção de uma escala com um modelo interpretativo que demonstra a evolução da piora da qualidade de vida em cinco níveis. Quanto aos parâmetros dos itens, houve bom desempenho daqueles referentes ao estado somático, pois apresentaram melhor poder de discriminar os indivíduos com pior qualidade de vida. Os itens relacionados ao estado mental foram os que contribuíram com menor quantidade de informação psicométrica no MINICHAL. CONCLUSÕES: Conclui-se que o instrumento é indicado para a identificação da deterioração da qualidade de vida em hipertensão arterial. A análise do MINICHAL pela Teoria da Resposta ao Item permitiu identificar novas facetas desse instrumento ainda não abordadas em estudos anteriores.

Design and validation of an aircraft seat comfort scale using item response theory.

This article aims to evaluate the psychometric properties of a scale that measures aircraft seat comfort. Factor analysis was used to study data variances. Psychometric quality was checked by using Item Response Theory. The sample consisted of 1500 passengers who completed a questionnaire at a Brazilian airport. Full information factor analysis showed the presence of one dominant factor explaining 34% of data variance. The scale generated covered all levels of comfort data, from 'no comfort' to 'maximum comfort'. The results show that the passengers consider there is comfort, but this is very minimal when these passengers have to perform their desired activities. It tends to increase when aspects of the aircraft seating are improved and positive emotions are elicited. Comfort peaks when pleasure is experienced and passenger expectations are exceeded (maximum comfort). This outcome seems consistent with the literature. Further research is advised to compare the outcome of this questionnaire with other research methods, and to check if the questionnaire is sensitive enough and whether its conclusions are useful in practice.

Impact of pecan nut shell aqueous extract on the oxidative properties of margarines during storage.

BACKGROUND: The oxidative properties of margarines supplemented with pecan nut shell extract, rosemary extract and butylated hydroxytoluene (BHT) were investigated. RESULTS: The extracts of pecan nut shell and rosemary showed a high content of total phenolics and condensed tannins (93 and 102.9 mg GAE g-1 and 46 and 38.9 mg CE g-1 respectively) as well as a high antioxidant activity (1257 and 2306 µmol TEAC g-1 and 293 and 856 mg TEAC g-1 by ABTS and DPPH methods respectively). Gallic acid, chlorogenic acid, p-hydroxybenzoic acid, epicatechin and epicatechin gallate were identified in the pecan nut shell extract. Peroxide and p-anisidine values of 3.75-4.43 meq kg-1 and 1.22-2.73 respectively, Totox values of 9.88-10.8 and specific extinction values of 4.38-4.59 and 0.92-0.94 at 232 and 268 nm respectively were observed after 8 months of storage in the studied samples. CONCLUSION: Margarines supplemented with pecan nut shell extract, rosemary extract or BHT during prolonged storage were found to be of equal quality within the degree of confidence limits. The extract of pecan nut shell may be considered as a natural product replacement for the synthetic antioxidant BHT. © 2016 Society of Chemical Industry.

Measuring the quality of life in hypertension according to Item Response Theory / Medição da qualidade de vida em hipertensão arterial segundo a Teoria da Resposta ao Item

ABSTRACT OBJECTIVE To analyze the Miniquestionário de Qualidade de Vida em Hipertensão Arterial (MINICHAL – Mini-questionnaire of Quality of Life in Hypertension) using the Item Response Theory. METHODS This is an analytical study conducted with 712 persons with hypertension treated in thirteen primary health care units of Fortaleza, State of Ceará, Brazil, in 2015. The steps of the analysis by the Item Response Theory were: evaluation of dimensionality, estimation of parameters of items, and construction of scale. The study of dimensionality was carried out on the polychoric correlation matrix and confirmatory factor analysis. To estimate the item parameters, we used the Gradual Response Model of Samejima. The analyses were conducted using the free software R with the aid of psych and mirt. RESULTS The analysis has allowed the visualization of item parameters and their individual contributions in the measurement of the latent trait, generating more information and allowing the construction of a scale with an interpretative model that demonstrates the evolution of the worsening of the quality of life in five levels. Regarding the item parameters, the items related to the somatic state have had a good performance, as they have presented better power to discriminate individuals with worse quality of life. The items related to mental state have been those which contributed with less psychometric data in the MINICHAL. CONCLUSIONS We conclude that the instrument is suitable for the identification of the worsening of the quality of life in hypertension. The analysis of the MINICHAL using the Item Response Theory has allowed us to identify new sides of this instrument that have not yet been addressed in previous studies.

RESUMO OBJETIVO Analisar o Miniquestionário de Qualidade de Vida em Hipertensão Arterial (MINICHAL) por meio da Teoria da Resposta ao Item. MÉTODOS Estudo analítico realizado com 712 pessoas com hipertensão arterial atendidas em 13 unidades de atenção primária em saúde de Fortaleza, CE, em 2015. As etapas da análise pela Teoria da Resposta ao Item foram: avaliação da dimensionalidade, estimação dos parâmetros dos itens e construção da escala. O estudo da dimensionalidade foi realizado sobre a matriz de correlação policórica e análise fatorial confirmatória. Para a estimação dos parâmetros dos itens, foi utilizado o Modelo de Resposta Gradual de Samejima. As análises foram conduzidas no software livre R com o auxílio dos pacotes psych e mirt. RESULTADOS A análise permitiu a visualização dos parâmetros dos itens e suas contribuições individuais na mensuração do traço latente, gerando mais informação, permitindo a construção de uma escala com um modelo interpretativo que demonstra a evolução da piora da qualidade de vida em cinco níveis. Quanto aos parâmetros dos itens, houve bom desempenho daqueles referentes ao estado somático, pois apresentaram melhor poder de discriminar os indivíduos com pior qualidade de vida. Os itens relacionados ao estado mental foram os que contribuíram com menor quantidade de informação psicométrica no MINICHAL. CONCLUSÕES Conclui-se que o instrumento é indicado para a identificação da deterioração da qualidade de vida em hipertensão arterial. A análise do MINICHAL pela Teoria da Resposta ao Item permitiu identificar novas facetas desse instrumento ainda não abordadas em estudos anteriores.

Interaction levels between comfort and discomfort in aircraft seats.

BACKGROUND: Although comfort and discomfort on seats have been widely investigated, their nature is still not well described by literature and it is not known exactly how the interaction between these two phenomena happens. OBJECTIVE: To investigate the multidimensional nature of comfort and discomfort in aircraft seats as well as their levels of interaction. METHODS: A comfort-discomfort questionnaire has been given to 1500 passengers in Brazil. RESULTS: The results brought evidence that comfort and discomfort are different phenomena with a strong negative correlation. At extreme levels, the presence of comfort implies the absence of discomfort; however at the other levels of comfort (minimum to moderate) there is the presence of discomfort. Estimating the scores given by the passengers has allowed them to be placed at scales of comfort and discomfort with their different levels. However, no passenger has achieved the levels of maximum comfort or of maximum discomfort. CONCLUSIONS: It is possible to infer that comfort, as much as discomfort are multidimensional phenomena and must be evaluated through scales with different levels, since at the extreme levels there is no interaction between the phenomena, but at the intermediate levels the passengers could perceive comfort and discomfort at the same time.

[Instrument to measure adherence in hypertensive patients: contribution of Item Response Theory]. / Instrumento mensurador de adesao para hipertensos: contribuicao da Teoria da Resposta ao Item.

OBJECTIVE: To analyze, by means of "Item Response Theory", an instrument to measure adherence to t treatment for hypertension. METHODS: Analytical study with 406 hypertensive patients with associated complications seen in primary care in Fortaleza, CE, Northeastern Brazil, 2011 using "Item Response Theory". The stages were: dimensionality test, calibrating the items, processing data and creating a scale, analyzed using the gradual response model. A study of the dimensionality of the instrument was conducted by analyzing the polychoric correlation matrix and factor analysis of complete information. Multilog software was used to calibrate items and estimate the scores. RESULTS: Items relating to drug therapy are the most directly related to adherence while those relating to drug-free therapy need to be reworked because they have less psychometric information and low discrimination. The independence of items, the small number of levels in the scale and low explained variance in the adjustment of the models show the main weaknesses of the instrument analyzed. The "Item Response Theory" proved to be a relevant analysis technique because it evaluated respondents for adherence to treatment for hypertension, the level of difficulty of the items and their ability to discriminate between individuals with different levels of adherence, which generates a greater amount of information. CONCLUSIONS: The instrument analyzed is limited in measuring adherence to hypertension treatment, by analyzing the "Item Response Theory" of the item, and needs adjustment. The proper formulation of the items is important in order to accurately measure the desired latent trait.

Instrumento mensurador de adesao para hipertensos: contribuicao da Teoria da Resposta ao Item / Instrumento medidor de adhesion para hipertensos: contribucion de la Teoria de la Respuesta al Item / Instrument to measure adherence in hypertensive patients: contribution of Item Response Theory

OBJETIVO: Analisar instrumento de medição da adesão ao tratamento da hipertensão por meio da "Teoria da Resposta ao Item". MÉTODOS: Estudo analítico com 406 hipertensos com complicações associadas, atendidos na atenção básica em Fortaleza, CE, 2011, pela "Teoria da Resposta ao Item". As etapas de execução foram: teste de dimensionalidade, calibração dos itens; tratamento dos dados e construção da escala, analisadas com base no modelo de resposta gradual. Estudo da dimensionalidade do instrumento foi feito pela análise da matriz de correlação policórica e análise fatorial de informação completa. Utilizou-se o software Multilog para calibração dos itens e estimação dos escores. RESULTADOS: Os itens referentes ao tratamento medicamentoso foram os mais diretamente relacionados à adesão, enquanto aqueles referentes ao tratamento não medicamentoso precisam ser reformulados, pois possuíram menor quantidade de informação psicométrica e baixa discriminação. A independência dos itens, o reduzido número de níveis da escala e as baixas variâncias explicadas no ajuste dos modelos mostraram as principais fragilidades do instrumento analisado. A "Teoria da Resposta ao Item" mostrou-se relevante para análise, pois avaliou o respondente quanto à adesão ao tratamento da hipertensão, ao nível de dificuldade dos itens e à sua capacidade de discriminação entre indivíduos com diferentes níveis de adesão, o que gerou maior quantidade de informação. CONCLUSÕES: O instrumento analisado é limitado para medir a adesão ao tratamento da hipertensão, mediante análise pela "Teoria da Resposta ao Item", e necessita de ajustes. A adequada formulação dos ...

OBJETIVO: Analizar instrumento de medición de la adhesión al tratamiento de hipertensión por medio de la "Teoría de la Respuesta al Ítem". MÉTODOS: Estudio analítico con 406 hipertensos con complicaciones asociadas, atendidos en la asistencia básica en Fortaleza, CE, Brasil, 2001 por la "Teoría de Respuesta al Ítem". Las etapas de ejecución fueron: prueba de dimensionalidad, calibración de los ítems; tratamiento de los datos y construcción de la escala, analizadas con base en el modelo de respuesta gradual. Estudio de la dimensionalidad del instrumento fue hecho por análisis de la matriz de correlación policórica y análisis factorial de información completa. Se utilizó el software Multilog para calibración de los ítems y estimación de los escores. RESULTADOS: Los ítems referentes al tratamiento medicamentoso fueron los más directamente relacionados con la adhesión, mientras que aquellos referentes al tratamiento no medicamentoso precisan ser reformulados, pues presentaron menor cantidad de información psicométrica y baja discriminación. La independencia de los ítems, el reducido número de niveles de escala y las bajas varianzas explicadas en el ajuste de los modelos mostraron las principales fragilidades del instrumento analizado. La Teoría de la Respuesta al Ítem se mostró relevante para el análisis, ya que evaluó al respondiente cuanto a la adhesión al tratamiento de la hipertensión, al nivel de dificultad de los ítems y a su capacidad de discriminación entre individuos con diferentes niveles de adhesión, lo que generó mayor cantidad de información. CONCLUSIONES: El instrumento analizado es limitado para medir la adhesión al tratamiento de la hipertensión, mediante análisis por la "Teoría ...

OBJECTIVE: To analyze, by means of "Item Response Theory", an instrument to measure adherence to t treatment for hypertension. METHODS: Analytical study with 406 hypertensive patients with associated complications seen in primary care in Fortaleza, CE, Northeastern Brazil, 2011 using "Item Response Theory". The stages were: dimensionality test, calibrating the items, processing data and creating a scale, analyzed using the gradual response model. A study of the dimensionality of the instrument was conducted by analyzing the polychoric correlation matrix and factor analysis of complete information. Multilog software was used to calibrate items and estimate the scores. RESULTS: Items relating to drug therapy are the most directly related to adherence while those relating to drug-free therapy need to be reworked because they have less psychometric information and low discrimination. The independence of items, the small number of levels in the scale and low explained variance in the adjustment of the models show the main weaknesses of the instrument analyzed. The "Item Response Theory" proved to be a relevant analysis technique because it evaluated respondents for adherence to treatment for hypertension, the level of difficulty of the items and their ability to discriminate between individuals with different levels of adherence, which generates a greater amount of information. CONCLUSIONS: The instrument analyzed is limited in measuring adherence to hypertension treatment, by analyzing the "Item Response Theory" of the item, and needs adjustment. The proper formulation of the items is important in order to accurately measure the desired latent trait. .

[Validation of the equations that estimate the resting metabolic rate in adolescent girls]. / Validação das equações que estimam a taxa metabólica de repouso em adolescentes meninas.

OBJECTIVES: The objective of the study is to analyze the validity of the prediction equations for the resting metabolic rate (RMR) proposed by Harris and Benedicti (1919), Schofield (1985), WHO/FAO/ UNU (1985), Henry and Rees (1991), Molnár and cols. (1995), Tverskaya and cols. (1998) and Müller and cols. (2004) in adolescent girls (51 girls between 10 and 17 years of age). SUBJECTS AND METHODS: The following anthropometric variables were measured: body weight, stature, body fat mass (absolute and percentage), body lean mass (absolute and percentage) as well as the consumption ofVO2 and production ofVCO2 that were substituted in Weir's (1949) equation which was considered the RMR standard method in this study. The following statistical procedures were carried out: paired t-test (p < 0.05); constant error (CE) with a less than 5% difference and Bland and Altman's (1986) graphical analysis. RESULTS: The equations proposed by Tverskaya and cols. (1998) and Müller and cols. (2004) were the only equations that presented significant differences between the averages. However, only the equations proposed by Henry and Rees (1991) and Molnár and cols. (1995) produced a constant error of less than 5%. However, Bland and Altman's (1986) graphical analysis showed that independently of the equation there is no agreement between the equations and the standard method. CONCLUSIONS: The study indicates that none of the equations meet all the stipulated criteria and that thus have no validity in the calculation of the RMR.

Validação das equações que estimam a taxa metabólica de repouso em adolescentes meninas / Validation of the equations that estimate the resting metabolic rate in adolescent girls

OBJETIVOS: O objetivo deste estudo é analisar a validade das equações de predição da taxa metabólica de repouso (TMR) propostas por Harris e Benedicti (1919), Schofield (1985), WHO/FAO/UNU (1985), Henry e Rees (1991), Molnár e cols. (1995), Tverskaya e cols. (1998) e Müller e cols. (2004) em adolescentes meninas. SUJEITOS E MÉTODOS: Para tanto, avaliaram-se 51 meninas entre 10 e 17 anos, sendo mensuradas as seguintes variáveis: massa corporal, estatura, massa gorda (absoluta e percentual) e massa magra (absoluta e percentual), bem como os valores do consumo de VO2 e produção de VCO2 que foram substituídos na equação de Weir (1949) considerada, neste estudo, como método padrão da TMR. Realizaram-se os seguintes procedimentos estatísticos: teste "t" pareado (p < 0,05); erro constante (EC) com diferença menor que 5 por cento e análise gráfica de Bland e Altman (1986). RESULTADOS: As equações propostas por Tverskaya e cols. (1998) e Müller e cols. (2004) foram as únicas que apresentaram diferenças significativas entre as médias. No entanto, somente as equações propostas por Henry e Rees (1991) e Molnár e cols. (1995) obtiveram erro constante inferior a 5 por cento. Porém, as análises gráficas de Bland e Altman (1986) revelaram que, independentemente da equação, não há concordância entre as equações e o método padrão. CONCLUSÕES: O estudo indicou que as equações não aprovaram nos critérios estipulados e que, portanto, não possuem validade no cálculo da TMR.

OBJECTIVES: The objective of the study is to analyze the validity of the prediction equations for the resting metabolic rate (RMR) proposed by Harris and Benedicti (1919), Schofield (1985), WHO/FAO/ UNU (1985), Henry and Rees (1991), Molnár and cols. (1995), Tverskaya and cols. (1998) and Müller and cols. (2004) in adolescent girls (51 girls between 10 and 17 years of age). SUBJECTS AND METHODs: The following anthropometric variables were measured: body weight, stature, body fat mass (absolute and percentage), body lean mass (absolute and percentage) as well as the consumption ofVO2 and production ofVCO2 that were substituted in Weir's (1949) equation which was considered the RMR standard method in this study. The following statistical procedures were carried out: paired t-test (p < 0.05); constant error (CE) with a less than 5 percent difference and Bland and Altman's (1986) graphical analysis. RESULTS: The equations proposed by Tverskaya and cols. (1998) and Müller and cols. (2004) were the only equations that presented significant differences between the averages. However, only the equations proposed by Henry and Rees (1991) and Molnár and cols. (1995) produced a constant error of less than 5 percent. However, Bland and Altman's (1986) graphical analysis showed that independently of the equation there is no agreement between the equations and the standard method. CONCLUSIONS: The study indicates that none of the equations meet all the stipulated criteria and that thus have no validity in the calculation of the RMR.