Should we use logistic mixed model analysis for the effect estimation in a longitudinal RCT with a dichotomous outcome variable?

Background: Within epidemiology both mixed model analysis and Generalised Estimating Equations (GEE analysis) are frequently used to analyse longitudinal RCT data. With a continuous outcome, both methods lead to more or less the same results, but with a dichotomous outcome the results are totally different. The purpose of the present study is to evaluate the performance of a logistic mixed model analysis and a logistic GEE analysis and to give an advice which of the two methods should be used. Methods: Two real life RCT datasets with and without missing data were used to perform this evaluation. Regarding the logistic mixed model analysis also two different estimation procedures were compared to each other. Results: The regression coefficients obtained from the two logistic mixed model analyses were different from each other, but were always higher then the regression coefficients derived from a logistic GEE analysis. Because this also holds for the standard errors, the corresponding p-values were more or less the same. It was further shown that the effect estimates derived from a logistic mixed model analysis were an overestimation of the ‘real’ effect estimates. Conclusions:  Although logistic mixed model analysis is widely used for the analysis of longitudinal RCT data, this article shows that logistic mixed model analysis should not be used when one is interested in the magnitude of the regression coefficients (i.e. effect estimates)

Taping patients with clinical signs of subacromial impingement syndrome: the design of a randomized controlled trial

<p>Abstract</p> <p>Background</p> <p>Shoulder problems are a common complaint of the musculoskeletal system. Physical therapists treat these patients with different modalities such as exercise, massage, and shoulder taping. Although different techniques have been described, the effectiveness of taping has not yet been established. The aim of this study is to assess the effectiveness and cost-effectiveness of usual physical therapy care in combination with a particular tape technique for subacromial impingement syndrome of the shoulder compared to usual physical therapy care without this tape technique in a primary healthcare setting.</p> <p>Methods and design</p> <p>An economic evaluation alongside a randomized controlled trial will be conducted. A sample of 140 patients between 18 and 65 years of age with a diagnosis of subacromial impingement syndrome (SAIS) as assessed by physical therapists will be recruited. Eligible patients will be randomized to either the intervention group (usual care in combination with the particular tape technique) or the control group (usual care without this tape technique). In both groups, usual care will consist of individualized physical therapy care. The primary outcomes will be shoulder-specific function (the Simple Shoulder Test) and pain severity (11-point numerical rating scale). The economic evaluation will be performed using a societal perspective. All relevant costs will be registered using cost diaries. Utilities (Quality Adjusted Life Years) will be measured using the EuroQol. The data will be collected at baseline, and 4, 12, and 26 weeks follow-up.</p> <p>Discussion</p> <p>This pragmatic study will provide information about the effectiveness and cost-effectiveness of taping in patients presenting with clinical signs of SAIS.</p> <p>Trial registration</p> <p>Trial registration number: <a href="http://www.trialregister.nl/trialreg/admin/rctview.asp?TC=2575">NTR2575</a></p

Measurement model choice influenced randomized controlled trial results

Objective In randomized controlled trials (RCTs), outcome variables are often patient-reported outcomes measured with questionnaires. Ideally, all available item information is used for score construction, which requires an item response theory (IRT) measurement model. However, in practice, the classical test theory measurement model (sum scores) is mostly used, and differences between response patterns leading to the same sum score are ignored. The enhanced differentiation between scores with IRT enables more precise estimation of individual trajectories over time and group effects. The objective of this study was to show the advantages of using IRT scores instead of sum scores when analyzing RCTs. Study Design and Setting Two studies are presented, a real-life RCT, and a simulation study. Both IRT and sum scores are used to measure the construct and are subsequently used as outcomes for effect calculation. Results The bias in RCT results is conditional on the measurement model that was used to construct the scores. A bias in estimated trend of around one standard deviation was found when sum scores were used, where IRT showed negligible bias. Conclusion Accurate statistical inferences are made from an RCT study when using IRT to estimate construct measurements. The use of sum scores leads to incorrect RCT result

Agreement and Reliability of a Symptom Modification Test Cluster for Patients With Subacromial Pain Syndrome

Objectives: To identify if a plausible theoretical construct exists for a test cluster in a group of patients with subacromial pain syndrome presenting with glenohumeral internal rotation deficit (GIRD); determine the intertester agreement and reliability of the proposed test cluster; determine if there are any meaningful relationships between the test cluster and the component tests for the entire sample; and determine if there are any differences in disability on the Dutch version of the shoulder pain and disability index between participants with a positive and negative test cluster. Methods: This study is a retrospective secondary analysis of data that were collected to determine the interrater agreement and reliability of clinical tests for assessment of patients with shoulder pain in primary care. Results: The test cluster total agreement and negative specific agreement was 87.8 and 90.4%, respectively. The prevalence-adjusted bias-adjusted kappa for the test cluster was substantial at 0.76. There were statistically significant meaningful relationships (≥0.50) between GIRD and the test cluster for Tester A (Phi = 0.71, p \u3c .01) and Tester B (Phi = 0.82, p \u3c .01). No differences in disability were identified between those with a positive and negative test cluster. Conclusion: The test cluster described in this study may be a reliable means of identifying a subgroup of patients with subacromial pain syndrome related to GIRD. Future research should look to validate this test cluster prospectively

What characterizes people who have an unclear classification using a treatment-based classification algorithm for low back pain? A cross-sectional study

Background. A treatment-based classification algorithm for low back pain (LBP) was created to help clinicians select treatments to which people are most likely to respond. To allow the algorithm to classify all people with LBP, additional criteria can help therapists make decisions for people who do not clearly fit into a subgroup (ie, unclear classifications). Recent studies indicated that classifications are unclear for approximately 34% of people with LBP. Objective. To guide improvements in the algorithm, it is imperative to determine whether people with unclear classifications are different from those with clear classifications. Design. This study was a secondary analysis of data from 3 previous studies investigating the algorithm. Methods. Baseline data from 529 people who had LBP were used (3 discrete cohorts). The primary outcome was type of classification, that is, clear or unclear. Univariate logistic regression was used to determine which participant variables were related to having an unclear classification. Results. People with unclear classifications had greater odds of being older (odds ratio [OR]=1.01, 95% confidence interval [CI]=1.003-1.033), having a longer duration of LBP (OR=1.001, 95% CI=1.000 -1.001), having had a previous episode(s) of LBP (OR=1.61, 95% CI=1.04 -2.49), having fewer fear-avoidance beliefs related to both work (OR=0.98, 95% CI=0.96-0.99) and physical activity (OR=0.98, 95% CI=0.96-0.996), and having less LBP-related disability (OR=0.98, 95% CI=0.96- 0.99) than people with clear classifications. Limitations. Studies from which participant data were drawn had different inclusion criteria and clinical settings. Conclusions. People with unclear classifications appeared to be less affected by LBP (less disability and fewer fear avoidance beliefs), despite typically having a longer duration of LBP. Future studies should investigate whether modifying the algorithm to exclude such people or provide them with different interventions improves outcomes

Physicians using spinal manipulative treatment in the Netherlands: A description of their characteristics and their patients

Background: Various health care professionals apply Spinal Manipulative Treatment (SMT) in daily practice. While the characteristics of chiropractors and manual therapists and the characteristics of their patient populations are well described, there is little research about physicians who use SMT techniques. A distinct group of physicians in The Netherlands has been trained in musculoskeletal (MSK) medicine, which includes the use of SMT. Our objective was to describe the characteristics of these physicians and their patient population. Methods: All registered MSK physicians were approached with questionnaires and telephone interviews to collect data about their characteristics. Data about patient characteristics were extracted from a web-based register. In this register physicians recorded basic patient data (age, gender, the type and duration of the main complaint, concomitant complaints and the type of referral) at the first consultation. Patients were invited to fill in web-based questionnaires to provide baseline data about previous treatments and the severity of their main complaint. Functional impairment was measured with Patient Reported Outcome Measures (PROMs). Results: Questionnaires were sent to 138 physicians of whom 90 responded (65%). Most physicians were trained in MSK medicine after a career in other medical specialities. They reported to combine their SMT treatment with a variety of diagnostic and treatment options part of which were only permissible for physicians, such as prescription medication and injections. The majority of patients presented with complaints of long duration (62.1% > 1 year), most frequently low back pain (48.1%) or neck pain (16.9%), with mean scores of 6.0 and 6.2, respectively, on a 0 to10 numerical rating scale (NRS) for pain intensity. Mean scores on all PROMs showed moderate impairment. Patients most frequently reported previous treatment by physical therapists (68.1%), manual therapists (37.7%) or chiropractors (17.0%). Conclusion: Our study showed that MSK physicians in The Netherlands used an array of SMT techniques. They embedded their SMT techniques in a broad array of other diagnostic and treatment options, part of which were limited to medical doctors. Most patients consulted MSK physicians with spinal pain of long duration with moderate functional impairment

Physicians using spinal manipulative treatment in the Netherlands:A description of their characteristics and their patients

Background: Various health care professionals apply Spinal Manipulative Treatment (SMT) in daily practice. While the characteristics of chiropractors and manual therapists and the characteristics of their patient populations are well described, there is little research about physicians who use SMT techniques. A distinct group of physicians in The Netherlands has been trained in musculoskeletal (MSK) medicine, which includes the use of SMT. Our objective was to describe the characteristics of these physicians and their patient population. Methods: All registered MSK physicians were approached with questionnaires and telephone interviews to collect data about their characteristics. Data about patient characteristics were extracted from a web-based register. In this register physicians recorded basic patient data (age, gender, the type and duration of the main complaint, concomitant complaints and the type of referral) at the first consultation. Patients were invited to fill in web-based questionnaires to provide baseline data about previous treatments and the severity of their main complaint. Functional impairment was measured with Patient Reported Outcome Measures (PROMs). Results: Questionnaires were sent to 138 physicians of whom 90 responded (65%). Most physicians were trained in MSK medicine after a career in other medical specialities. They reported to combine their SMT treatment with a variety of diagnostic and treatment options part of which were only permissible for physicians, such as prescription medication and injections. The majority of patients presented with complaints of long duration (62.1% > 1 year), most frequently low back pain (48.1%) or neck pain (16.9%), with mean scores of 6.0 and 6.2, respectively, on a 0 to10 numerical rating scale (NRS) for pain intensity. Mean scores on all PROMs showed moderate impairment. Patients most frequently reported previous treatment by physical therapists (68.1%), manual therapists (37.7%) or chiropractors (17.0%). Conclusion: Our study showed that MSK physicians in The Netherlands used an array of SMT techniques. They embedded their SMT techniques in a broad array of other diagnostic and treatment options, part of which were limited to medical doctors. Most patients consulted MSK physicians with spinal pain of long duration with moderate functional impairment

What characterizes people who have an unclear classification using a treatment-based classification algorithm for low back pain? A cross-sectional study

Conclusions. People with unclear classifications appeared to be less affected by LBP (less disability and fewer fear avoidance beliefs), despite typically having a longer duration of LBP. Future studies should investigate whether modifying the algorithm to exclude such people or provide them with different interventions improves outcomes.

Rigid shoulder taping with physiotherapy in patients with subacromial pain syndrome: A randomized controlled trial

OBJECTIVE: To assess the effectiveness of individualized physiotherapy in combination with rigid taping compared with individualized physiotherapy alone in patients with subacromial pain syndrome. DESIGN: A prospective randomized trial with concealed allocation. PATIENTS: A total of 140 patients between 18 and 65 years of age from primary physiotherapy settings. METHODS: The intervention group received individualized physiotherapy and shoulder taping. The control group received individualized physiotherapy only. Primary outcomes were: pain intensit (numerical rating scale) and functioning (Simple Shoulder Test). Secondary outcomes were: global perceived effect and patient-specific complaints. Data were collected at baseline, and at 4, 12 and 26 weeks' follow-up. RESULTS: During the 6-month follow-up period multilevel analysis showed a significant difference between groups favouring the control group on pain intensity (p = 0.02), but not on functioning. Regarding secondary outcomes, a significant difference between groups was found favouring the intervention group for global perceived effect (p = 0.02), but not for patient-specific complaints. CONCLUSION: Rigid shoulder taping, as used in this study, cannot be recommended for improving physiotherapy outcomes in people with subacromial pain syndrome