Background: Advanced statistical modeling techniques may help predict health outcomes. However, it is not the case that these modeling techniques always outperform traditional techniques such as regression techniques. In this study, external validation was carried out for five modeling strategies for the prediction of the disability of community-dwelling older people in the Netherlands. Methods: We analyzed data from five studies consisting of community-dwelling older people in the Netherlands. For the prediction of the total disability score as measured with the Groningen Activity Restriction Scale (GARS), we used fourteen predictors as measured with the Tilburg Frailty Indicator (TFI). Both the TFI and the GARS are self-report questionnaires. For the modeling, five statistical modeling techniques were evaluated: general linear model (GLM), support vector machine (SVM), neural net (NN), recursive partitioning (RP), and random forest (RF). Each model was developed on one of the five data sets and then applied to each of the four remaining data sets. We assessed the performance of the models with calibration characteristics, the correlation coefficient, and the root of the mean squared error. Results: The models GLM, SVM, RP, and RF showed satisfactory performance characteristics when validated on the validation data sets. All models showed poor performance characteristics for the deviating data set both for development and validation due to the deviating baseline characteristics compared to those of the other data sets. Conclusion: The performance of four models (GLM, SVM, RP, RF) on the development data sets was satisfactory. This was also the case for the validation data sets, except when these models were developed on the deviating data set. The NN models showed a much worse performance on the validation data sets than on the development data sets.
DOCUMENT
BackgroundPatients undergoing total knee arthroplasty (TKA) often experience strength deficits both pre- and post-operatively. As these deficits may have a direct impact on functional recovery, strength assessment should be performed in this patient population. For these assessments, reliable measurements should be used. This study aimed to determine the inter- and intrarater reliability of hand-held dynamometry (HHD) in measuring isometric knee strength in patients awaiting TKA.MethodsTo determine interrater reliability, 32 patients (81.3% female) were assessed by two examiners. Patients were assessed consecutively by both examiners on the same individual test dates. To determine intrarater reliability, a subgroup (n = 13) was again assessed by the examiners within four weeks of the initial testing procedure. Maximal isometric knee flexor and extensor strength were tested using a modified Citec hand-held dynamometer. Both the affected and unaffected knee were tested. Reliability was assessed using the Intraclass Correlation Coefficient (ICC). In addition, the Standard Error of Measurement (SEM) and the Smallest Detectable Difference (SDD) were used to determine reliability.ResultsIn both the affected and unaffected knee, the inter- and intrarater reliability were good for knee flexors (ICC range 0.76-0.94) and excellent for knee extensors (ICC range 0.92-0.97). However, measurement error was high, displaying SDD ranges between 21.7% and 36.2% for interrater reliability and between 19.0% and 57.5% for intrarater reliability. Overall, measurement error was higher for the knee flexors than for the knee extensors.ConclusionsModified HHD appears to be a reliable strength measure, producing good to excellent ICC values for both inter- and intrarater reliability in a group of TKA patients. High SEM and SDD values, however, indicate high measurement error for individual measures. This study demonstrates that a modified HHD is appropriate to evaluate knee strength changes in TKA patient groups. However, it also demonstrates that modified HHD is not suitable to measure individual strength changes. The use of modified HHD is, therefore, not advised for use in a clinical setting.
MULTIFILE
Purpose: The purpose of this study was to validate optimized algorithm parameter settings for step count and physical behavior for a pocket worn activity tracker in older adults during ADL. Secondly, for a more relevant interpretation of the results, the performance of the optimized algorithm was compared to three reference applications Methods: In a cross-sectional validation study, 20 older adults performed an activity protocol based on ADL with MOXMissActivity versus MOXAnnegarn, activPAL, and Fitbit. The protocol was video recorded and analyzed for step count and dynamic, standing, and sedentary time. Validity was assessed by percentage error (PE), absolute percentage error (APE), Bland-Altman plots and correlation coefficients. Results: For step count, the optimized algorithm had a mean APE of 9.3% and a correlation coefficient of 0.88. The mean APE values of dynamic, standing, and sedentary time were 15.9%, 19.9%, and 9.6%, respectively. The correlation coefficients were 0.55, 0.91, and 0.92, respectively. Three reference applications showed higher errors and lower correlations for all outcome variables. Conclusion: This study showed that the optimized algorithm parameter settings can more validly estimate step count and physical behavior in older adults wearing an activity tracker in the trouser pocket during ADL compared to reference applications.
DOCUMENT
INTRODUCTION: In patients with cancer, low muscle mass has been associated with a higher risk of fatigue, poorer treatment outcomes, and mortality. To determine body composition with computed tomography (CT), measuring the muscle quantity at the level of lumbar 3 (L3) is suggested. However, in patients with cancer, CT imaging of the L3 level is not always available. Thus far, little is known about the extent to which other vertebra levels could be useful for measuring muscle status. In this study, we aimed to assess the correlation of the muscle quantity and quality between any vertebra level and L3 level in patients with various tumor localizations.METHODS: Two hundred-twenty Positron Emission Tomography (PET)-CT images of patients with four different tumor localizations were included: 1. head and neck ( n = 34), 2. esophagus ( n = 45), 3. lung ( n = 54), and 4. melanoma ( n = 87). From the whole body scan, 24 slices were used, i.e., one for each vertebra level. Two examiners contoured the muscles independently. After contouring, muscle quantity was estimated by calculating skeletal muscle area (SMA) and skeletal muscle index (SMI). Muscle quality was assessed by calculating muscle radiation attenuation (MRA). Pearson correlation coefficient was used to determine whether the other vertebra levels correlate with L3 level. RESULTS: For SMA, strong correlations were found between C1-C3 and L3, and C7-L5 and L3 ( r = 0.72-0.95). For SMI, strong correlations were found between the levels C1-C2, C7-T5, T7-L5, and L3 ( r = 0.70-0.93), respectively. For MRA, strong correlations were found between T1-L5 and L3 ( r = 0.71-0.95). DISCUSSION: For muscle quantity, the correlations between the cervical, thoracic, and lumbar levels are good, except for the cervical levels in patients with esophageal cancer. For muscle quality, the correlations between the other levels and L3 are good, except for the cervical levels in patients with melanoma. If visualization of L3 on the CT scan is absent, the other thoracic and lumbar vertebra levels could serve as a proxy to measure muscle quantity and quality in patients with head and neck, esophageal, lung cancer, and melanoma, whereas the cervical levels may be less reliable as a proxy in some patient groups.
DOCUMENT
We show how to estimate a Cronbach's alpha reliability coefficient in Stata after running a principal component or factor analysis. Alpha evaluates to what extent items measure the same underlying content when the items are combined into a scale or used for latent variable. Stata allows for testing the reliability coefficient (alpha) of a scale only when all items receive homogenous weights. We present a user-written program that computes reliability coefficients when implementation of principal component or factor analysis shows heterogeneous item loadings. We use data on management practices from Bloom and Van Reenen (2010) to explain how to implement and interpret the adjusted internal consistency measure using afa.
DOCUMENT
OBJECTIVE: To investigate the level of agreement of the behavioural mapping method with an accelerometer to measure physical activity of hospitalized patients. DESIGN: A prospective single-centre observational study. SETTING: A university medical centre in the Netherlands. SUBJECTS: Patients admitted to the hospital. MAIN MEASURES: Physical activity of participants was measured for one day from 9 AM to 4 PM with the behavioural mapping method and an accelerometer simultaneously. The level of agreement between the percentages spent lying, sitting and moving from both measures was evaluated using the Bland-Altman method and by calculating Intraclass Correlation Coefficients. RESULTS: In total, 30 patients were included. Mean (±SD) age was 63.0 (16.8) years and the majority of patients were men (n = 18). The mean percentage of time (SD) spent lying was 47.2 (23.3) and 49.7 (29.8); sitting 42.6 (20.5) and 40.0 (26.2); and active 10.2 (6.1) and 10.3 (8.3) according to the accelerometer and observations, respectively. The Intraclass Correlation Coefficient and mean difference (SD) between the two measures were 0.852 and -2.56 (19.33) for lying; 0.836 and 2.60 (17.72) for sitting; and 0.782 and -0.065 (6.23) for moving. The mean difference between the two measures is small (⩽2.6%) for all three physical activity levels. On patient level, the variation between both measures is large with differences above and below the mean of ⩾20% being common. CONCLUSION: The overall level of agreement between the behavioural mapping method and an accelerometer to identify the physical activity levels 'lying', 'sitting' and 'moving' of hospitalized patients is reasonable.
DOCUMENT
The main aim of this study was to determine the agreement in classification between the modified KörperKoordinations Test für Kinder (KTK3+) and the Athletic Skills Track (AST) for measuring fundamental movement skill levels (FMS) in 6- to 12-year old children. 3,107 Dutch children (of which 1,625 are girls) between 6 and 12 years of age (9.1 ± 1.8 years) were tested with the KTK3+ and the AST. The KTK3+ consists of three items from the KTK and the Faber hand-eye coordination test. Raw scores from each subtest were transformed into percentile scores based on all the data of each grade. The AST is an obstacle course consisting of 5 (grades 3 till 5, 6–9 years) or 7 (grades 6 till 8, 9–12 years) concatenated FMS that should be performed as quickly as possible. The outcome measure is the time needed to complete the track. A significant bivariate Pearson correlation coefficient of 0.51 was found between the percentile sum score of the KTK3+ and the time to complete the AST, indicating that both tests measure a similar construct to some extent. Based on their scores, children were classified into one of five categories: <5, 5–15, 16–85, 86–95 or >95%. Cross tabs revealed an agreement of 58.8% with a Kappa value of 0.15 between both tests. Less than 1% of the children were classified more than two categories higher or lower. The moderate correlation between the KTK3+ and the AST and the low classification agreement into five categories of FMS stress the importance to further investigate the test choice and the measurement properties (i.e., validity and reliability) of both tools. PE teachers needs to be aware of the context in which the test will be conducted, know which construct of motor competence they want to measure and know what the purpose of testing is (e.g., screening or monitoring). Based on these considerations, the most appropriate assessment tool can be chosen.
MULTIFILE
Validity and Reproducibility of a New Treadmill Protocol: The Fitkids Treadmill Test. Med. Sci. Sports Exerc., Vol. 47, No. 10, pp. 2241–2247, 2015. Purpose: This study aimed to investigate the validity and reproducibility of a new treadmill protocol in healthy children and adolescents: the Fitkids Treadmill Test (FTT). Methods: Sixty-eight healthy children and adolescents (6–18 yr) were randomly divided into a validity group (14 boys and 20 girls; mean T SD age, 12.9 T 3.6 yr) that performed the FTT and Bruce protocol, both with respiratory gas analysis within 2 wk, and a reproducibility group (19 boys and 15 girls; mean T SD age, 13.5 T 3.5 yr) that performed the FTT twice within 2 wk. A subgroup of 21 participants within the reproducibility group performed both FTT with respiratory gas analysis. Time to exhaustion (TTE) was the main outcome of the FTT. Results: V˙ O2peak measured during the FTT showed excellent correlation with V˙ O2peak measured during the Bruce protocol (r = 0.90; P G 0.01). Backward multiple regression analysis provided the following prediction equations for V˙ O2peak (LIminj1) for boys and girls, respectively: V˙ O2peak FTT ¼ j0:748 þ ð0:117 TTEFTTÞ þ ð0:032 bodymassÞ þ 0:263, and V˙ O2peak FTT ¼ j0:748 þ ð0:117 TTEFTTÞ þ ð0:032 bodymassÞ [R2 ¼ 0:935; SEE ¼ 0:256LI min j1]. Cross-validation of the regression model showed an R2 value of 0.76. Reliability statistics for the FTT showed an intraclass correlation coefficient of 0.985 (95% confidence interval, 0.971–0.993; P G 0.001) for TTE. Bland–Altman analysis showed a mean bias of j0.07 min, with limits of agreement between +1.30 and j1.43 min. Conclusions: Results suggest that the FTT is a useful treadmill protocol with good validity and reproducibility in healthy children and adolescents. Exercise performance on the FTT and body mass can be used to adequately predict V˙ O2peak when respiratory gas analysis is not available.
DOCUMENT
Background. Adequate and user-friendly instruments for assessing physical function and disability in older adults are vital for estimating and predicting health care needs in clinical practice. The Late-Life Function and Disability Instrument Computer Adaptive Test (LLFDICAT) is a promising instrument for assessing physical function and disability in gerontology research and clinical practice. Objective. The aims of this study were: (1) to translate the LLFDI-CAT to the Dutch language and (2) to investigate its validity and reliability in a sample of older adults who spoke Dutch and dwelled in the community. Design. For the assessment of validity of the LLFDI-CAT, a cross-sectional design was used. To assess reliability, measurement of the LLFDI-CAT was repeated in the same sample. Methods. The item bank of the LLFDI-CAT was translated with a forward-backward procedure. A sample of 54 older adults completed the LLFDI-CAT, World Health Organization Disability Assessment Schedule 2.0, RAND 36-Item Short-Form Health Survey physical functioning scale (10 items), and 10-Meter Walk Test. The LLFDI-CAT was repeated in 2 to 8 days (mean4.5 days). Pearson’s r and the intraclass correlation coefficient (ICC) (2,1) were calculated to assess validity, group-level reliability, and participant-level reliability. Results. A correlation of .74 for the LLFDI-CAT function scale and the RAND 36-Item Short-Form Health Survey physical functioning scale (10 items) was found. The correlations of the LLFDI-CAT disability scale with the World Health Organization Disability Assessment Schedule 2.0 and the 10-Meter Walk Test were .57 and .53, respectively. The ICC (2,1) of the LLFDI-CAT function scale was .84, with a group-level reliability score of .85. The ICC (2,1) of the LLFDI-CAT disability scale was .76, with a group-level reliability score of .81. Limitations. The high percentage of women in the study and the exclusion of older adults with recent joint replacement or hospitalization limit the generalizability of the results. Conclusions. The Dutch LLFDI-CAT showed strong validity and high reliability when used to assess physical function and disability in older adults dwelling in the community.
MULTIFILE
Abstract: Electronic and electrical waste (e-waste) is growing fast. The purpose of this study is to examine young consumers’ purchase intention of refurbished electronic devices (REDs) such as laptop, tablet, mobile phone and game console. From literature review the factors that influence young consumers’ purchase intention were identified as ‘environmental awareness’, ‘social acceptance’, ‘seller/brand reputation and availability’, and ‘affordability and value’. For each factor a few statements were developed and used as independent variables in a questionnaire. One statement was added about purchase intention as dependent variable. A Pearson correlation coefficient test us showed a clear positive correlation of ‘environmental awareness’ and ‘affordability and value’ with the intention to purchase REDs, but not for the other two factors. This analysis contributes to knowledge on young consumers’ perceptions of refurbished electronic devices and can inform the design of innovative value propositions and new business models for REDs that contribute to a circular economy
MULTIFILE
