On the proper use of the crossover design in clinical trials: part 18 of a series on evaluation of scientific publications

Plaque Removal and Gingival Health after Use of a Novel Dental Gel: A Clinical Study

Background

Goal of this in vivo prospective, randomized, controlled, double-blinded, cross over study was to compare the level of plaque control and gingivitis after use of a novel dental gel (test) vs. A Triclosan/copolymer dentifrice (control).

Methods

After coronal polishing, 22 subjects with moderate gingivitis were randomly assigned to brush twice daily with test or control dentifrice for the first study Arm. Plaque, gingival and sulcus bleeding indices were recorded at baseline, week 2 and week 4. Professional coronal polishing was repeated, and then subjects brushed with the second dentifrice for 4 weeks. Clinical indices were again recorded at Baseline, week 2 and week 4. The effects of each dentifrice on clinical indices were compared using Student’s t-test.

Results

Brushing with the test gel produced significantly greater levels of plaque reduction versus the Triclosan/copolymer control dentifrice at each time point. 45% less plaque was measured after 4 weeks of test agent use than after control agent use (p<0.000000005). A significant reduction in gingival inflammation from test vs control agent over w\4 weeks was also observed (p=0.000342).

Conclusions

An activated edathamil dental gel formulation provides effective plaque control and reduced gingival inflammation compared to a Triclosan/Co-polymer dental gel. Practical Implications: A novel dental gel formulation that does not contain abrasives, detergents or antimicrobials may provide effective plaque control and support gingival health.

Effects of an L-arginine-based multi ingredient product on endothelial function in subjects with mild to moderate hypertension and hyperhomocysteinemia - a randomized, double-blind, placebo-controlled, cross-over trial

Background

Nutrition plays an important role in prevention and management of cardiovascular diseases (CVD) in early stages. Recent research demonstrated beneficial effects of various nutritional ingredients on vascular health. The aim of the current study was to evaluate the effects of an L-arginine-based multi ingredient product (AbMIP) on vascular function.

Methods

Twenty-five male and female subjects, aged between 45 and 65 years with elevated blood pressure and hyperhomocysteinemia were included in this cross-over trial. Subjects were randomly assigned to one of the two sequence groups (AbMIP -placebo or placebo – AbMIP). AbMIP and placebo were taken for 4 weeks, each. Endothelial function under fasting conditions, blood pressure, postprandial endothelial function after consumption of a high fat meal, homocysteine, asymmetric dimethyl arginine (ADMA) and Hba1c were determined.

Results

AbMIP significantly improved fasting endothelial function determined by EndoPAT™ when compared to placebo (p = 0.047). Similarly, homocysteine levels were significantly decreased after verum supplementation when compared to placebo (p < 0.0001). Systolic blood pressure decreased significantly under AbMIP (p = 0.002) and the reduction was more pronounced when compared to placebo. However, due to placebo-effects no significant difference could be found between groups (p = 0.586). The effects on postprandial endothelial function were stronger for AbMIP when compared with placebo but did not reach significance (p = 0.201). No significant effects of AbMIP were observed regarding HbA1c, ADMA and diastolic blood pressure.

Conclusions

Due to improvement on endothelial function, decrease of elevated homocysteine levels and excellent tolerability, AbMIP was demonstrated to be a beneficial option for dietary treatment of endothelial dysfunction and hyperhomocysteinemia in early stages of CVD.

Trial registration

The clinical trials.gov identifier is NCT02392767, November 14, 2014.

Hand-held Fan Airflow Stimulation Relieves Dyspnea in Lung Cancer Patients

Objective:

The main symptom of lung cancer is dyspnea which can lead to depression, anxiety, limited independent activities, and decreased quality of life. The purpose of this study was to identify the effect of airflow stimulation from a hand-held fan as nonpharmacological palliative intervention on dyspnea in patients with lung cancer.

Methods:

This study used open, randomized, controlled, crossover trial design involved 21 participants. Diaphragmatic breathing technique was used in control arm.

Results:

Wilcoxon test result showed that airflow stimulation significantly influenced dyspnea scale (P = 0.003) and respiratory rate (RR) (P = 0.008). Combination of airflow stimulation and diaphragmatic breathing can lower both dyspnea scale and RR significantly (P < 0.0001).

Conclusions:

This combination can be applied on nonhypoxemic dyspneic lung cancer patients.

Inter-Individual Variability in the Adaptive Responses to Endurance and Sprint Interval Training: A Randomized Crossover Study

The current study examined the adaptive response to both endurance (END) and sprint interval training (SIT) in a group of twenty-one recreationally active adults. All participants completed three weeks (four days/ week) of both END (30 minutes at ~65% VO2peak work rate (WR) and SIT (eight, 20-second intervals at ~170% VO2peak WR separated by 10 seconds of active rest) following a randomized crossover study design with a three-month washout period between training interventions. While a main effect of training was observed for VO2peak, lactate threshold, and submaximal heart rate (HR), considerable variability was observed in the individual responses to both END and SIT. No significant positive relationships were observed between END and SIT for individual changes in any variable. Non-responses were determined using two times the typical error (TE) of measurement for VO2peak (0.107 L/min), lactate threshold (15.7 W), and submaximal HR (10.7bpm). Non-responders in VO2peak, lactate threshold, and submaximal HR were observed following both END and SIT, however, the individual patterns of response differed following END and SIT. Interestingly, all individuals responded in at least one variable when exposed to both END and SIT. These results suggest that the individual response to exercise training is highly variable following different training protocols and that the incidence of non-response to exercise training may be reduced by changing the training stimulus for non-responders to three weeks of END or SIT.

Transcranial direct current stimulation improves clinical symptoms in adolescents with attention deficit hyperactivity disorder

Anodal transcranial direct current stimulation (tDCS) of the prefrontal cortex has repeatedly been shown to improve working memory. As patients with attention deficit hyperactivity disorder (ADHD) are characterized by both underactivation of the prefrontal cortex and deficits in working memory that correlate with clinical symptoms, it is hypothesized that the modulation of prefrontal activity with tDCS in patients with ADHD increases performance in working memory and reduces symptoms of ADHD. To test this hypothesis, fifteen adolescents with ADHD (12-16 years old, three girls and 12 boys) were treated according to the randomized, double-blinded, sham-controlled, crossover design with either 1 mA anodal tDCS over the left dorsolateral prefrontal cortex or with the sham protocol 5 days each with a 2 weeks pause between these conditions. Anodal tDCS caused a significant reduction in clinical symptoms of inattention and impulsivity in adolescents with ADHD compared to sham stimulation. The clinical effects were supported by a significant reduction in inattention and hyperactivity in a standardized working memory test (QbTest). The described effects were more pronounced 7 days after the end of stimulation, a fact which emphasizes the long-lasting clinical and neuropsychological changes after tDCS. This study provides the first evidence that tDCS may reduce symptoms of ADHD and improve neuropsychological functioning in adolescents and points on the potential of tDCS as a form of treatment for ADHD.

Effects of a Novel Dental Gel on Enamel Surface Recovery from Acid Challenge

BACKGROUND

Objective was to evaluate the in vivo effects of a novel dental gel (Livionex gelR) vs. a comparison dental gel on the surfaces of pre-eroded enamel chips.

METHODS

On days 1-5, after toothbrushing with dentifrice, nine subjects each wore 8 enamel chips mounted on a palatal appliance for 4 h. Enamel blocks were pre-demineralized daily. After 2 day washout, subjects repeated the protocol using fresh chips and the second toothpaste on days 8-12. Samples were evaluated using electron microscopy.

RESULTS

Ten standardized enamel surface photomicrographs/sample (total 1440 images) were evaluated for signs of erosion visually and on a scale of 0-3 by 1 evaluator. No significant differences were found between the 2 groups (p>0.32, 95% C.I.). Minimal surface erosion on approx. 15% of sample area was visible in both groups.

CONCLUSION

The enamel surface appeared similar after usage of a test or control dentifrice. Based on this study, the test formulation did not affect enamel surface recovery from an erosive challenge.

PRACTICAL IMPLICATIONS

Dentifrices can contribute to maintaining a healthy enamel surface. An all-natural dental gel formulation with novel anti-plaque mechanism achieved similar recovery from acid challenge to enamel as a control gel.

Long-term Rehabilitation in Patients With Acquired Brain Injury

BACKGROUND

Patients with acquired brain injury who have been discharged from inpatient neurological rehabilitation often continue to suffer from limited independence, participation, and quality of life. Participation-focused outpatient treatment (in German: teilhabeorientierte ambulan.

METHODS

In a randomized, controlled trial, 53 patients who had sustained an acquired brain injury approximately four years earlier were allotted to two different sequences of treatment (26 TEAM/control, 27 control/TEAM). The primary endpoint was the achievement of an individual participation goal one month after the start of treatment. The secondary endpoints included independence in everyday activities, health-related quality of life, participation, and need for nursing care. The intervention was four weeks long and was carried out on an outpatient basis (19.4 ± 1.3 hours per week). Patients in the control group were treated in a manner resembling usual current care. All endpoints were evaluated in a per-protocol (PP) analysis of data from 47 patients. For confirmation, an intention-to-treat (ITT) analysis was also carried out for the primary endpoint and for independence in everyday activities.

RESULTS

According to the PP analysis, TEAM patients achieved their individual participation goals at 1 month more frequently than control patients receiving standard treatment (61% vs. 21%; p = 0.008) and improved more with respect to independence in everyday activities. The difference between TEAM and standard treatment was +7.3 points on the FIM (Functional Independence Measure) scale (95% confidence interval [2.8; 11.8]; p = 0.0024). The superiority of TEAM was confirmed by the ITT analysis (achievement of the participation goal, TEAM vs. standard treatment: 54% vs. 19%, p = 0.0103). Moreover, improvements were seen at 12 months in quality of life, participation, and the need for nursing care.

CONCLUSION

The TEAM rehabilitation program can help patients in the chronic phase of acquired brain injury achieve participation goals that are relevant to everyday life. An adjustment of the care structure in Germany to include such intensive goal-oriented rehabilitation programs would lead to a more effective mobilization of these patients' potential for long-term rehabilitation.

The influence of insoles with a peroneal pressure point on the electromyographic activity of tibialis anterior and peroneus longus during gait

Background

Peroneus longus acts as a foot evertor and pronator, thus ensuring stability of the talocrural joint by curbing inversion movement of the rearfoot. Increased activation of the peroneus longus muscle in the stance phase could have a stabilising effect on the ankle joint. This study aimed to determine whether the activity of the peroneus longus muscle could be increased by the targeted use of a specially formed lateral pressure element in a customised orthopaedic insole.

Methods

This was a laboratory-based study that utilised a randomised crossover design. Thirty-four healthy participants walked along a walkway in neutral footwear wearing a control insole or a sensorimotor insole with a lateral pressure point adjacent to the tendon of the peroneus longus muscle. The electromyographic muscle activity of the peroneus longus and tibialis anterior muscles was measured using surface electromyography. Contact with the ground was recorded via two pressure sensors under the sole of the shoe. Muscle activity during the stance phase was analysed in the time and amplitude domains and compared statistically with paired t-tests for both insole types.

Results

In 27 out of the 34 participants, an additional activity peak of the peroneus longus muscle was observed in the loading response phase with the sensorimotor insole, which reached its maximum at 29.7 % (±4.5 %) of the stance phase. When averaged over all 34 participants, the integrated electromyographic output for the peroneus longus in the mid-stance phase revealed a significant higher activity (p < 0.001, post hoc power = 0.98, effect size: Cohen’s d = 0.71) with the sensorimotor insole (18.1 ± 11.3 % MVCs) than with the control insole (11.2 ± 7.7 % MVCs). No significant effects were established for the other gait phases or for the tibialis anterior.

Conclusions

An increase of muscle activity of the peroneus longus muscle was observed during the loading response and mid-stance phase, when orthopedic insoles with a lateral pressure point were worn. We conclude that the pressure point changes afferent information and leads to an increased peroneus longus activation in the time interval in which the pressure point exerted pressure on the peroneal tendon.

Decreased Symptoms without Augmented Skin Blood Flow in Subjects with RLS/WED after Vibration Treatment

STUDY OBJECTIVES

Vascular disturbances leading to tissue hypoxia have been named as a possible cause for RLS/WED. Vibration to the whole body (WBV) in subjects with RLS/WED results in increased skin blood flow (SBF). The aims of this investigation were to (1) determine if a two-week treatment with WBV will decrease symptoms associated with RLS/WED and, (2) if so, determine if the mechanism for improvement in symptoms is related to an increase in SBF, as measured in flux.

METHODS

Eleven subjects with RLS/WED underwent 2 weeks of 14-minute intermittent WBV and a 2-week sham treatment in randomized order. Pre and post intervention RLS symptom severity were compared. Baseline SBF was compared between subjects with RLS/WED and an age- and sex-matched control group. A crossover design (aim 1) and a matched case-control design and repeated measures design (aim 2) were used. The data analyses consisted of 2-sample and paired t-tests; where applicable we used a standard crossover design adjustment.

RESULTS

WBV did significantly decrease symptoms associated with RLS/WED compared to baseline data and compared to sham treatment. The baseline flux was significantly lower in RLS/WED subjects than matched controls, but this deficit was negated with WBV. There was no increase in resting SBF over the 2 weeks of treatment.

CONCLUSIONS

Subjects with RLS/WED have decreased SBF but are able to increase flux to the same level as normal subjects with WBV. A 2-week intervention with WBV decreases symptoms associated with RLS/WED, but this does not seem to be related to an increase in resting SBF.

Randomized controlled trials - a matter of design

Randomized controlled trials (RCTs) are the hallmark of evidence-based medicine and form the basis for translating research data into clinical practice. This review summarizes commonly applied designs and quality indicators of RCTs to provide guidance in interpreting and critically evaluating clinical research data. It further reflects on the principle of equipoise and its practical applicability to clinical science with an emphasis on critical care and neurological research. We performed a review of educational material, review articles, methodological studies, and published clinical trials using the databases MEDLINE, PubMed, and ClinicalTrials.gov. The most relevant recommendations regarding design, conduction, and reporting of RCTs may include the following: 1) clinically relevant end points should be defined a priori, and an unbiased analysis and report of the study results should be warranted, 2) both significant and nonsignificant results should be objectively reported and published, 3) structured study design and performance as indicated in the Consolidated Standards of Reporting Trials statement should be employed as well as registration in a public trial database, 4) potential conflicts of interest and funding sources should be disclaimed in study report or publication, and 5) in the comparison of experimental treatment with standard care, preplanned interim analyses during an ongoing RCT can aid in maintaining clinical equipoise by assessing benefit, harm, or futility, thus allowing decision on continuation or termination of the trial.

Establishing the effectiveness, cost-effectiveness and student experience of a Simulation-based education Training program On the Prevention of Falls (STOP-Falls) among hospitalised inpatients: a protocol for a randomised controlled trial

INTRODUCTION

Simulation-based education (SBE) is now commonly used across health professional disciplines to teach a range of skills. The evidence base supporting the effectiveness of this approach for improving patient health outcomes is relatively narrow, focused mainly on the development of procedural skills. However, there are other simulation approaches used to support non-procedure specific skills that are in need of further investigation. This cluster, cross-over randomised controlled trial with a concurrent economic evaluation (cost per fall prevented) trial will evaluate the effectiveness, cost-effectiveness and student experience of health professional students undertaking simulation training for the prevention of falls among hospitalised inpatients. This research will target the students within the established undergraduate student placements of Monash University medicine, nursing and allied health across Peninsula Health acute and subacute inpatient wards.

METHODS AND ANALYSIS

The intervention will train the students in how to provide the Safe Recovery program, the only single intervention approach demonstrated to reduce falls in hospitals. This will involve redevelopment of the Safe Recovery program into a one-to-many participant SBE program, so that groups of students learn the communication skills and falls prevention knowledge necessary for delivery of the program. The primary outcome of this research will be patient falls across participating inpatient wards, with secondary outcomes including student satisfaction with the SBE and knowledge gain, ward-level practice change and cost of acute/rehabilitation care for each patient measured using clinical costing data.

ETHICS AND DISSEMINATION

The Human Research Ethics Committees of Peninsula Health (LRR/15/PH/11) and Monash University (CF15/3523-2015001384) have approved this research. The participant information and consent forms provide information on privacy, storage of results and dissemination. Registration of this trial has been completed with the Australian and New Zealand Clinical Trials Registry: ACTRN12615000817549. This study protocol has been prepared according to the Standard Protocol Items: Recommendations for Interventional Trials (SPIRIT) checklist.

TRIAL REGISTRATION NUMBER

ACTRN12615000817549; Pre-results.

Model-Based Assessment of Alternative Study Designs in Pediatric Trials. Part I: Frequentist Approaches

Alternative designs can increase the feasibility of pediatric trials when compared to classical parallel designs (PaD). In this work we present a model-based approach based on clinical trial simulations for the comparison of PaD with the alternative sequential, crossover, and randomized withdrawal (RWD) designs. Study designs were evaluated in terms of: type I and II errors, sample size per arm (SS), trial duration (TD), treatment exposures, and parameter estimate precision (EP). The crossover requires the lowest SS and TD, although it implies higher placebo and no treatment exposures. RWD maximizes exposure to active treatment while minimizing that to placebo, but requires the largest SS. SS of sequential designs can sometimes be smaller than the crossover one, although with poorer EP. This pharmacometric framework allows a multiscale comparison of alternative study designs that can be used for design selection in future pediatric trials.

A Crossover Design for Comparative Efficacy: A 36-Week Randomized Trial of Bevacizumab and Ranibizumab for Diabetic Macular Edema

PURPOSE

To investigate the comparative efficacy of bevacizumab (Avastin) and ranibizumab (Lucentis; both Genentech, Inc, South San Francisco, CA) for diabetic macular edema (DME) using a crossover study design.

DESIGN

Randomized, double-masked, 36-week, 3-period crossover clinical trial.

PARTICIPANTS

Fifty-six subjects with DME involving the center of the macula in one or both eyes.

METHODS

Monthly intravitreous injections of bevacizumab (1.25 mg) or ranibizumab (0.3 mg).

MAIN OUTCOME MEASURES

Comparison of mean changes in visual acuity and central retinal thickness, tested using a linear mixed-effects model.

RESULTS

Based on the linear mixed-effects model, the 3-month estimated mean improvement in visual acuity was 5.3 letters for bevacizumab and 6.6 letters for ranibizumab (difference, 1.3 letters; P = 0.039). Estimated change in optical coherence tomography (OCT) central subfield mean thickness (CSMT) was -89 μm for bevacizumab and -137 μm for ranibizumab (difference, 48 μm; P < 0.001). Incorporating cumulative treatment benefit, the model yielded a predicted 36-week (9-month) average improvement in visual acuity of 7.1 letters (95% confidence interval [CI], 5.0-9.2) for bevacizumab and 8.4 letters (95% CI, 6.3-10.5) for ranibizumab, and a change in OCT CSMT of -128 μm (95% CI, -155 to -100) for bevacizumab and -176 μm (95% CI, -202 to -149) for ranibizumab. There was no significant treatment-by-period interaction (i.e., treatment difference was constant in all 3 periods), nor was there a significant differential carryover effect from one period to the next.

CONCLUSIONS

This trial demonstrated a statistically significant but small relative clinical benefit of ranibizumab compared with bevacizumab for treatment of DME, using a markedly reduced sample size relative to a full comparative efficacy study. The effects on visual acuity and central retinal thickness for the 2 drugs are consistent with those reported at 1 year for the concurrent parallel-group trial by the Diabetic Retinopathy Clinical Research Network testing bevacizumab, ranibizumab, and aflibercept for DME. The 3-period crossover design allowed for meaningful and efficient comparison, suggesting that this approach may be useful for future comparative efficacy studies of anti-vascular endothelial growth factor drugs for DME.

Molecular adsorbent recirculating system and single-pass albumin dialysis in liver failure--a prospective, randomised crossover study

Background

The aim of extracorporeal albumin dialysis (ECAD) is to reduce endogenous toxins accumulating in liver failure. To date, ECAD is conducted mainly with the Molecular Adsorbents Recirculating System (MARS). However, single-pass albumin dialysis (SPAD) has been proposed as an alternative. The aim of this study was to compare the two devices with a prospective, single-centre, non-inferiority crossover study design with particular focus on reduction of bilirubin levels (primary endpoint) and influence on paraclinical and clinical parameters (secondary endpoints) associated with liver failure.

Methods

Patients presenting with liver failure were screened for eligibility and after inclusion were randomly assigned to be started on either conventional MARS or SPAD (with 4 % albumin and a dialysis flow rate of 700 ml/h). Statistical analyses were based on a linear mixed-effects model.

Results

Sixty-nine crossover cycles of ECAD in 32 patients were completed. Both systems significantly reduced plasma bilirubin levels to a similar extent (MARS: median −68 μmol/L, interquartile range [IQR] −107.5 to −33.5, p = 0.001; SPAD: −59 μmol/L, −84.5 to +36.5, p = 0.001). However, bile acids (MARS: −39 μmol/L, −105.6 to −8.3, p < 0.001; SPAD: −9 μmol/L, −36.9 to +11.4, p = 0.131), creatinine (MARS: −24 μmol/L, −46.5 to −8.0, p < 0.001; SPAD: −2 μmol/L, −9.0 to +7.0/L, p = 0.314) and urea (MARS: −0.9 mmol/L, −1.93 to −0.10, p = 0.024; SPAD: −0.1 mmol/L, −1.0 to +0.68, p = 0.523) were reduced and albumin-binding capacity was increased (MARS: +10 %, −0.8 to +20.9 %, p < 0.001; SPAD: +7 %, −7.5 to +15.5 %, p = 0.137) only by MARS. Cytokine levels of interleukin (IL)-6 and IL-8 and hepatic encephalopathy were altered by neither MARS nor SPAD.

Conclusions

Both procedures were safe for temporary extracorporeal liver support. While in clinical practice routinely assessed plasma bilirubin levels were reduced by both systems, only MARS affected other paraclinical parameters (i.e., serum bile acids, albumin-binding capacity, and creatinine and urea levels). Caution should be taken with regard to metabolic derangements and electrolyte disturbances, particularly in SPAD using regional citrate anti-coagulation.

Trial registration

German Clinical Trials Register (www.drks.de) DRKS00000371. Registered 8 April 2010.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-015-1159-3) contains supplementary material, which is available to authorized users.

Effects of Ayurvedic Oil-Dripping Treatment with Sesame Oil vs. with Warm Water on Sleep: A Randomized Single-Blinded Crossover Pilot Study

OBJECTIVES

Ayurvedic oil-dripping treatment (Shirodhara) is often used for treating sleep problems. However, few properly designed studies have been conducted, and the quantitative effect of Shirodhara is unclear. This study sought to quantitatively evaluate the effect of sesame oil Shirodhara (SOS) against warm water Shirodhara (WWS) on improving sleep quality and quality of life (QOL) among persons reporting sleep problems.

METHODS

This randomized, single-blinded, crossover study recruited 20 participants. Each participant received seven 30-minute sessions within 2 weeks with either liquid. The washout period was at least 2 months. The Shirodhara procedure was conducted by a robotic oil-drip system. The outcomes were assessed by the Pittsburgh Sleep Quality Index (PSQI) for sleep quality, Epworth Sleepiness Scale (ESS) for daytime sleepiness, World Health Organization Quality of Life 26 (WHO-QOL26) for QOL, and a sleep monitor instrument for objective sleep measures. Changes between baseline and follow-up periods were compared between the two types of Shirodhara. Analysis was performed with generalized estimating equations.

RESULTS

Of 20 participants, 15 completed the study. SOS improved sleep quality, as measured by PSQI. The SOS score was 1.83 points lower (95% confidence interval [CI], -3.37 to -0.30) at 2-week follow-up and 1.73 points lower (95% CI, -3.84 to 0.38) than WWS at 6-week follow-up. Although marginally significant, SOS also improved QOL by 0.22 points at 2-week follow-up and 0.19 points at 6-week follow-up compared with WWS. After SOS, no beneficial effects were observed on daytime sleepiness or objective sleep measures.

CONCLUSIONS

This pilot study demonstrated that SOS may be a safe potential treatment to improve sleep quality and QOL in persons with sleep problems.

Optimal Cardiac Resynchronization Therapy Pacing Rate in Non-Ischemic Heart Failure Patients: A Randomized Crossover Pilot Trial

Background

The optimal pacing rate during cardiac resynchronization therapy (CRT) is unknown. Therefore, we investigated the impact of changing basal pacing frequencies on autonomic nerve function, cardiopulmonary exercise capacity and self-perceived quality of life (QoL).

Methods

Twelve CRT patients with non-ischemic heart failure (NYHA class II–III) were enrolled in a randomized, double-blind, crossover trial, in which the basal pacing rate was set at DDD-60 and DDD-80 for 3 months (DDD-R for 2 patients). At baseline, 3 months and 6 months, we assessed sympathetic nerve activity by microneurography (MSNA), peak oxygen consumption (pVO₂), N-terminal pro-brain natriuretic peptide (p-NT-proBNP), echocardiography and QoL.

Results

DDD-80 pacing for 3 months increased the mean heart rate from 77.3 to 86.1 (p = 0.001) and reduced sympathetic activity compared to DDD-60 (51±14 bursts/100 cardiac cycles vs. 64±14 bursts/100 cardiac cycles, p<0.05). The mean pVO₂ increased non-significantly from 15.6±6 mL/min/kg during DDD-60 to 16.7±6 mL/min/kg during DDD-80, and p-NT-proBNP remained unchanged. The QoL score indicated that DDD-60 was better tolerated.

Conclusion

In CRT patients with non-ischemic heart failure, 3 months of DDD-80 pacing decreased sympathetic outflow (burst incidence only) compared to DDD-60 pacing. However, Qol scores were better during the lower pacing rate. Further and larger scale investigations are indicated.

Trial Registration

ClinicalTrials.gov NCT02258061

Design, Analysis, and Reporting of Crossover Trials for Inclusion in a Meta-Analysis

Randomized crossover trials are clinical experiments in which participants are assigned randomly to a sequence of treatments and each participant serves as his/her own control in estimating treatment effect. We need a better understanding of the validity of their results to enable recommendations as to which crossover trials can be included in meta-analysis and for development of reporting guidelines.

Effectiveness of an audience response system on orthodontic knowledge retention of undergraduate dental students--a randomised control trial

Objective:: To determine the effect of an audience response system (ARS) on knowledge retention of dental students and to gauge student perceptions of using the ARS. Design:: Randomised control study. Setting:: School of Dentistry, Cardiff University. Participants:: Seventy four second-year dental students were stratified by gender and randomised anonymously to one of two groups. Methods:: One group received a lecture on orthodontic terminology and diagnosis in a traditional didactic format and the other received the same lecture integrated with ARS slides. Students completed an assessment of multiple-choice questions (MCQs) scored out of 20, before and immediately after the lecture. Students were also asked to complete a self-reported questionnaire on their perceptions of ARS. Results:: Both groups had statistically significant increases in MCQ scores post-lecture (ARS mean increase 3.6 SD2.0, 95% CI 2.2–3.5 and Didactic mean increase 2.9 SD2.3, 95% CI 2.8–4.3). A mixed-design analysis of variance showed that ARS led to an improved MCQ score (by 0.8 or 25%) compared to the didactic group, although this effect was not significant (P = 0.15). The effect of gender at baseline (P = 0.49), post-lecture (P = 0.73) and increase in MCQ score split by group (P = 0.46) was also not significant. Students reported that the ARS was easy to use, helped them engage with the lecture and encouraged them to work harder. Conclusion:: The ARS did not lead to a significant increase in short-term orthodontic knowledge recall of students compared with didactic teaching. However, the use of ARS within orthodontic teaching could make lectures more interactive and engaging.

Clarithromycin in γ-aminobutyric acid-Related hypersomnolence: A randomized, crossover trial

OBJECTIVE

Some central hypersomnolence syndromes are associated with a positive allosteric modulator of γ-aminobutyric acid (GABA)-A receptors in cerebrospinal fluid. Negative allosteric modulators of GABA-A receptors, including clarithromycin, have been reported to reduce sleepiness in these patients. We sought to systematically assess the effects of clarithromycin on objective vigilance and subjective sleepiness.

METHODS

This was a 5-week, randomized, placebo-controlled, double-blind, crossover trial of clarithromycin 500mg with breakfast and lunch, in patients with hypersomnolence syndromes (excluding narcolepsy with cataplexy) and evidence for abnormal cerebrospinal fluid potentiation of GABA-A receptors. The study occurred at a university-affiliated medical center. The primary outcome measure was median reaction time on the psychomotor vigilance task (PVT) at week 2 in each condition. Secondary outcomes included the Epworth Sleepiness Scale, Stanford Sleepiness Scale, Functional Outcomes of Sleep Questionnaire, Pittsburgh Sleep Quality Index, SF-36, and additional PVT measures.

RESULTS

Twenty-three patients began treatment. Three patients dropped out, and final analyses were performed on 20 complete cases. Median reaction time was not significantly different between clarithromycin and placebo. Subjective measures of sleepiness were significantly improved on clarithromycin versus placebo. Altered taste perception occurred, but was the only side effect more common on clarithromycin than placebo. No serious adverse events occurred.

INTERPRETATION

Subjective sleepiness, but not psychomotor vigilance, improved during a 2-week course of clarithromycin. Although additional studies are needed, this suggests that clarithromycin may be a reasonable treatment option in patients with treatment-refractory hypersomnolence. This trial was registered at ClinicalTrials.gov (NCT01146600) and supported by the American Sleep Medicine Foundation.

Muscular contraction mode differently affects autonomic control during heart rate matched exercise

The precise contributions of afferent feedback to cardiovascular and respiratory responses to exercise are still unclear. The aim of this crossover study was to assess whether and how autonomic cardiovascular and respiratory control differed in response to dynamic (DYN) and isometric contractions (ISO) at a similar, low heart rate (HR) level. Therefore, 22 healthy males (26.7 ± 3.6 yrs) performed two kinds of voluntary exercises at similar HR: ISO and DYN of the right quadriceps femoris muscle. Although HR was eqivalent (82 ± 8 bpm for DYN and ISO, respectively), rating of exertion, blood pressures, and rate pressure product were higher, whereas breathing frequency, minute ventilation, oxygen uptake and carbon dioxide output were significantly lower during ISO. Tidal volume, end-tidal partial pressures of O2 and CO2, respiratory exchange ratio and capillary blood lactate concentration were comparable between both contraction modes. Heart rate variability (HRV) indicators, SDNN, HF-Power and LF-Power, representing both vagal and sympathetic influences, were significantly higher during ISO. Sample entropy, a non-linear measure of HRV was also significantly affected by contraction mode. It can be concluded that, despite the same net effect on HR, the quality of cardiovascular control during low intensity exercise is significantly different between DYN and ISO. HRV analysis indicated a sympatho-vagal coactivation during ISO. Whether mechanoreceptor feedback alone, a change in central command, or the interaction of both mechanisms is the main contributor of the distinct autonomic responses to the different exercise modes remains to be elucidated.

Which treatment is better? Ascertaining patient preferences with crossover randomized controlled trials

CONTEXT

The difference in patient-reported outcomes between study arms can often be difficult to ascertain in randomized controlled trials (RCTs) using a parallel design because of wide interindividual variations in baseline characteristics and how patients interpret the outcome measures. Furthermore, the minimal clinically significant difference is often not available for many outcomes, and even when available, not individualized for each patient. Crossover RCTs are designed for intraindividual comparisons, which can address these issues by asking patients to directly compare the interventions with regard to effectiveness, adverse effects, and ease of use and to provide an overall choice.

OBJECTIVES

We discuss the key design elements for crossover trials, their advantages and disadvantages relative to parallel designs, and their utility in palliative care research using a number of case examples.

METHODS

This is a narrative review.

RESULTS

Crossover studies randomize patients to a sequence of treatments. In addition to facilitating intraindividual comparisons, they often require a smaller sample size for the same statistical power compared with parallel designs and are thus less costly. However, crossover studies are only feasible when the condition being studied is relatively stable and the intervention has a short-term effect. Crossover studies with inadequate washout periods may be difficult to interpret. The risk of attrition also may increase because of prolonged study duration.

CONCLUSION

By facilitating intraindividual comparisons and eliciting patient preferences, crossover studies can provide unique information on the superior intervention. Crossover designs should be considered for selected palliative care studies.

Design and rationale for the randomised, double-blinded, placebo-controlled Liraglutide to Improve corONary haemodynamics during Exercise streSS (LIONESS) crossover study

BACKGROUND

Glucagon-like peptide-1 is an incretin hormone essential for normal human glucose homeostasis. Expression of the glucagon-like peptide-1 receptor in the myocardium has fuelled growing interest in the direct and indirect cardiovascular effects of native glucagon-like peptide-1, its degradation product glucagon-like peptide-1(9-36), and the synthetic glucagon-like peptide-1 receptor agonists. Preclinical studies have demonstrated cardioprotective actions of all three compounds in the setting of experimental myocardial infarction and left ventricular systolic dysfunction. This has led to Phase 2 trials of native glucagon-like peptide-1 and incretin-based therapies in humans with and without Type 2 diabetes mellitus. These studies have demonstrated the ability of glucagon-like peptide-1, independent of glycaemic control, to positively modulate the metabolic and haemodynamic parameters of individuals with coronary artery disease and left ventricular systolic dysfunction. We aim to add to this growing body of evidence by studying the effect of chronic glucagon-like peptide-1 receptor activation on exercise-induced ischaemia in patients with chronic stable angina managed conservatively or awaiting revascularisation. The hypothesis being liraglutide, a subcutaneously injectable glucagon-like peptide-1 receptor agonist, is able to improve exercise haemodynamics in patients with obstructive coronary artery disease when compared with saline placebo.

METHODS AND DESIGN

The Liraglutide to Improve corONary haemodynamics during Exercise streSS (LIONESS) trial is an investigator-initiated single-centre randomised double-blinded placebo-controlled crossover proof-of-principle physiological study. Primary endpoints are change in rate pressure product at 0.1 mV ST-segment depression and change in degree of ST-segment depression at peak exercise during sequential exercise tolerance testing performed over a 6-week study period in which 26 patients will be randomised to either liraglutide or saline with crossover to the opposing regimen at week 3.

DISCUSSION

The study will be conducted in accordance with the principles of Good Clinical Practice and the Declaration of Helsinki. The local Research Ethics Committee and Medicines and Healthcare Products Regulatory Agency have approved the study.

TRIAL REGISTRATION

National Institute of Health Research Clinical Research Network (NIHR CRN) Portfolio ID 11112 and ClinicalTrials.gov Identifier NCT02315001.

Effects of krill oil on endothelial function and other cardiovascular risk factors in participants with type 2 diabetes, a randomized controlled trial

OBJECTIVE

The purpose of this trial was to evaluate the effect of krill oil supplementation, a source of ω-3 fatty acids, on cardiovascular disease risk factors and blood glucose control among participants with type 2 diabetes.

RESEARCH DESIGN AND METHODS

A randomized, double-blind controlled cross-over trial was employed. Outcomes assessed were: endothelial function, blood lipids, glucose, glycated hemoglobin, serum antioxidant level, C peptide, and calculated Homeostatic Model Assessment of Insulin Resistance (HOMA-IR) scores. Participants were randomized to either krill oil or olive oil supplementation for 4 weeks, underwent a 2-week washout period, and then crossed to the other supplementation for 4 weeks. All participants were then offered an additional 17 weeks of krill supplementation. Testing occurred at 3 time points: baseline, after first supplementation, and after second supplementation. Testing also occurred after an optional 17 weeks of krill oil supplementation. Difference scores were calculated for each participant in both sequences (ie, differences in outcome measures in the first and second period of the sequence). The mean and SD of the scores in the 2 sequence groups were used to test for differences between treatment effects at a significance level of p<0.05.

RESULTS

A total of 47 participants were included in the initial cross-over study. Participants who received krill oil for 4 weeks had an improvement in their endothelial function and a reduction in blood C peptide levels and HOMA scores as compared with the olive oil. A total of 34 participants completed the additional 17-week supplementation period. When compared with their respective baseline measures, these participants had a statistically significant improvement in endothelial function and blood high-density lipoprotein (HDL).

CONCLUSIONS

Krill oil may lead to moderate improvement of cardiovascular risks, specifically endothelial dysfunction and HDL in patients with type 2 diabetes.

TRIAL REGISTRATION NUMBER

Registered with ClinicalTrials.gov: NCT02091193.

Improvements in hand function in adults with chronic tetraplegia following a multiday 10-Hz repetitive transcranial magnetic stimulation intervention combined with repetitive task practice

BACKGROUND AND PURPOSE

Evidence suggests that the use of stimulation to increase corticomotor excitability improves hand function in persons with cervical spinal cord injury. We assessed effects of a multiday application of 10-Hz repetitive transcranial magnetic stimulation (rTMS) applied to the corticomotor hand area combined with repetitive task practice (RTP) in participants with tetraplegia and neurologically healthy participants.

METHODS

Using a double-blind, randomized, crossover design, 11 participants with chronic tetraplegia and 10 neurologically healthy participants received 3 sessions of 10-Hz rTMS+RTP and 3 sessions of sham-rTMS+RTP to the corticomotor hand region controlling the weaker hand. Repetitive transcranial magnetic stimulation was interleaved with RTP of a skilled motor task between pulse trains. Hand function (Jebsen-Taylor Hand Function Test, pinch, and grasp strength) and corticomotor excitability (amplitude of motor-evoked potential) were assessed before and after the rTMS+RTP and sham-rTMS+RTP phases. We assessed significance, using paired t tests on pre-post differences, and effect sizes, using the standardized response mean.

RESULTS

RTMS+RTP was associated with larger effect sizes compared with sham-rTMS+RTP for improvement in Jebsen-Taylor Hand Function Test for both the trained hand (standardized response mean = 0.85 and 0.42, respectively) and non-trained hand (0.55 and 0.31, respectively), and for grasp strength of the trained hand in the group with cervical spinal cord injury (0.67 and 0.39, respectively) alone. Effect sizes for all other measures were small and there were no statistical between-condition differences in the outcomes assessed.

DISCUSSION AND CONCLUSIONS

Repetitive transcranial magnetic stimulation may be a valuable adjunct to RTP for improving hand function in persons with tetraplegia. Higher stimulation dose (frequency, intensity, and the number of sessions) may be associated with larger effects.

VIDEO ABSTRACT AVAILABLE

(see Supplemental Digital Content 1, http://links.lww.com/JNPT/A82) for more insights from the authors.

Efficacy of omeprazole on cough, pulmonary function and quality of life of patients with sulfur mustard lung injury: A placebo-control, cross-over clinical trial study

BACKGROUND

Gastro-esophageal reflux disease (GERD) is prevalent and related to more severe disease in patients with respiratory problems. We evaluated the effects of antireflux therapy in warfare victims of exposure to Mustard gas with chronic cough.

MATERIALS AND METHODS

This randomized, double-blind, placebo-controlled, cross-over study was conducted on 45 cases of sulfur mustard injury with chronic cough (≥8 weeks) and GERD. Patients were randomized into two groups, receiving either 20 mg twice daily omeprazole-placebo (OP) or matching placebo (placebo-omeprazole [PO]) for 4 months, followed by a 1-month washout period and the alternative treatment for 4 months. Assessments included GERD and cough, quality of life, and pulmonary function using spirometry. Leicester Cough Questionnaire and SF-36 were used for measuring quality of life.

RESULTS

Patients in the OP group experienced a more decrease than those in the PO group in severity of Leicester cough scores during the first 4-month of trial. After crossing the groups, the OP group experienced an increase (P = 0.036) and the PO group experienced a nonsignificant decrease (P = 0.104) in the severity of scores. The OP group also experienced improvement in GERD symptoms and quality of life at the end of the trial, but changes in the PO group was not significant. There was no significant change in respiratory function indices in any groups.

CONCLUSION

Long-term treatment with high-dose omeprazole improved GERD as well as cough, and quality of life, but not changed respiratory function indices in sulfur mustard injured cases with respiratory symptoms.

Enhancing the delivery of resveratrol in humans: if low bioavailability is the problem, what is the solution?

Resveratrol has emerged as a leading candidate for improving healthspan through potentially slowing the aging process and preventing chronic diseases. The poor bioavailability of resveratrol in humans has been a major concern for translating basic science findings into clinical utility. Although a number of positive findings have emerged from human clinical trials, there remain many conflicting results, which may partially be attributed to the dosing protocols used. A number of theoretical solutions have been developed to improve the bioavailability of resveratrol, including consumption with various foods, micronized powders, combining it with additional phytochemicals, controlled release devices, and nanotechnological formulations. While laboratory models indicate these approaches all have potential to improve bioavailability of resveratrol and optimize its clinical utility, there is surprisingly very little data regarding the bioavailability of resveratrol in humans. If bioavailability is indeed a limitation in the clinical utility of resveratrol, there is a need to further explore methods to optimize bioavailability in humans. This review summarizes the current bioavailability data, focusing on data from humans, and provides suggested directions for future research in this realm.

[Cross stability in conventional shoes by the use of spring steel insoles: a pedobarographic effect study with observational application]

BACKGROUND

From an orthopedic point of view, wearing conventional ready to wear shoes negatively affects the front transverse arch of the human foot by forcing it into an unnatural inverted position.

OBJECTIVES

The aim of the present orthopedic application study was to conduct a standardized assessment of the biomechanical effect of a newly developed, longitudinally flexible and cross stable spring steel insole by means of pedobarographic measurements and by means of a supplementary questioning of the participants.

MATERIAL AND METHODS

In order to do this a total of 33 healthy adult participants were recruited in summer 2013. The randomized, blinded and controlled main study compared the cross stable insole made from spring steel with a flat, ordinary control insole made from ethylene vinyl acetate by means of pedobarographic in-shoe measurements at the forefoot. Additionally, the subjectively perceived effect of the steel insole with respect to comfort, restricted mobility and pain was assessed in a randomized, blinded and controlled ancillary study, using a cross-over design.

RESULTS

Both the plantar peak pressure and the plantar force-time integral were significantly higher with the spring steel insole, especially in the central forefoot. In the subsequent test phase lasting several weeks during which the participants were asked to wear the spring steel insole, they rarely complained about problems and in particular did not report negative effects regarding comfort, restricted mobility and pain compared to the ordinary control insoles.

CONCLUSION

The present study was conducted according to high methodological standards and proved for the first time that the tested spring steel insoles have a positive effect on the human forefoot. The cross stability increases the pressure in the median ball area, prevents the unnatural inverted position of the forefoot and thus creating an effect which is comparable to walking barefoot. As the participants did not judge this orthopedic effect of the cross stability as being uncomfortable, such an insole could be used a millionfold as a primary prevention in conventional shoes.

Applications of pressure control ventilation volume guaranteed during one-lung ventilation in thoracic surgery

OBJECTIVE

To explore the effects of ventilatory mode "pressure controlled ventilation-volume guaranteed" (PCV-VG) on the inspiratory pressures, oxygenation parameters and hemodynamics of patients during one lung ventilation (OLV) for thoracic surgery, compared with volume controlled ventilation (VCV).

METHODS

Twenty participants were recruited and equally assigned into two groups in a controlled, randomized, crossover design. Group A: VCV was performed initially and changed into PCV-VG after 30 min; Group B: In the reverse order. Blood gas analysis, peak inspiratory pressure (Ppeak), mean inspiratory pressure (Pmean), plateau inspiratory pressure (Plateau) were measured at four different time points: (1) 30 min after total lung ventilation (TLV); (2) 30 min after one lung ventilation (VCV or PCV-VG); (3) 30 min after shifting to the other ventilatory mode, and (4) 30 min after reconstruction of TLV.

RESULTS

The Ppeak, Plateau, and Pmean were significantly lower in PCV-VG compared with VCV. There was significant increase in arterial partial pressure of oxygen under PCV-VG.

CONCLUSION

In patients undergoing thoracic surgery with OLV, pressure controlled volume guaranteed mode of ventilation may have better effects by decreasing inspiratory pressure parameters and improving arterial oxygenation than volume controlled ventilation.

Foot massage and physiological stress in people with dementia: a randomized controlled trial

BACKGROUND

The anxiety associated with unfamiliar surroundings, the disorientation and mental confusion, and the social isolation that accompanies dementia can often create increased stress for people living in long-term care settings. Such a response is thought to affect the autonomic nervous system and result in emotional and physical symptoms of distress that may be manifested as agitation. There is the potential for such distress to influence the physiological response and in particular Blood Pressure and Heart Rate. A relaxation intervention such as massage may influence the physiological stress response.

METHODS

This randomized controlled trial aimed to compare the effect of foot massage (FM) versus a control activity (quiet presence, QP) on physiological stress response (i.e., blood pressure [BP] and heart rate [HR]) in people living with moderate-to-severe dementia in long-term-care settings.

RESULTS

Fifty-three residents were randomized to intervention (10-minute FM) or control group (QP). While the FM group experienced a greater reduction in HR than the control group, these reductions were not significantly different between groups (p=0.83; see Table 1 ), or across time (p=0.46). Both groups experienced a reduction in systolic BP and diastolic BP, while the mean reduction in systolic BP was greater for those in the FM group.

CONCLUSIONS

While the findings do not provide strong support for FM, the finding that both conditions allowed the person with dementia to rest in the presence of another human being is of importance in the care of people with dementia. The close presence of another person may in fact promote relaxation and therefore improve BP and HR measures.

Course of Hemoglobin and Hematocrit during and after Preparatory Plasmaphereses without and with Infusion of NaCl 0.9% 500 ml

BACKGROUND

The aim of this study was to evaluate the course of hemoglobin (HGB) concentration and hematocrit (HCT) in donor blood during and after preparatory plasmaphereses (PP) without NaCl and with an infusion of 500 ml 0.9% NaCl during PP.

METHODS

After informed consent 32 plasma donors were studied in a crossover design. They underwent PP once without NaCl infusion and once, on a different day, with infusion of 500 ml 0.9% NaCl. HGB concentration and HCT values in donor blood were analyzed using a Sysmex KX-21N analyzer. The values of HGB concentration and HCT before PP were set to 100%. Changes in HGB concentration and HCT were calculated in percent directly after PP, and after 24 and 72 h.

RESULTS

During PP, there was a notable change in HGB concentration (11.2 ± 4.0%) and HCT (11.6 ± 3.9%) in donor blood. The difference between the 2 samples without and with NaCl was highly significant (p < 0.001). After 24 and 72 h, all differences were reduced.

CONCLUSION

We observed significant changes in HGB concentration and HCT in donor blood during PP. We recommend a concomitant infusion of 500 ml 0.9% NaCl during PP to all donors.

Urinary concentrations and antibacterial activities of nitroxoline at 250 milligrams versus trimethoprim at 200 milligrams against uropathogens in healthy volunteers

Because of the increasing bacterial resistance of uropathogens against standard antibiotics, such as trimethoprim (TMP), older antimicrobial drugs, such as nitroxoline (NTX), should be reevaluated. This randomized crossover study investigated the urinary concentrations of parent drugs and their metabolites and their antibacterial activities (urinary inhibitory titers [UITs] and urinary bactericidal titers [UBTs]) against uropathogens at three different urinary pH values within 24 h in six healthy volunteers after a single oral dose of NTX at 250 mg versus TMP at 200 mg. In three additional volunteers, urinary bactericidal kinetics (UBK) were studied after oral administration of NTX at 250 mg three times a day. The mean urinary concentrations of NTX and NTX sulfate in 24 h were 0.012 to 0.507 mg/liter and 0.28 to 27.83 mg/liter, respectively. The mean urinary concentrations of TMP were 18.79 to 41.59 mg/liter. The antibacterial activity of NTX was higher in acidic urine than in alkaline urine, and that of TMP was higher in alkaline urine than in acidic urine. The UITs and UBTs of NTX were generally lower than those of TMP except for a TMP-resistant Escherichia coli strain, for which NTX showed higher UITs/UBTs than did TMP. UBK showed mainly bacteriostatic activity of NTX in urine. NTX exhibits mainly bacteriostatic activity and TMP also shows bactericidal activity in urine against susceptible strains. NTX is a more active antibacterial in acidic urine, and TMP is more active in alkaline urine. The cumulative effects of multiple doses or inhibition of bacterial adherence could not be evaluated. (This study has been registered at EudraCT under registration no. 2009-015631-32.).

Nigral stimulation for resistant axial motor impairment in Parkinson's disease? A randomized controlled trial

Gait and balance disturbances typically emerge in advanced Parkinson’s disease with generally limited response to dopaminergic medication and subthalamic nucleus deep brain stimulation. Therefore, advanced programming with interleaved pulses was put forward to introduce concomittant nigral stimulation on caudal contacts of a subthalamic lead. Here, we hypothesized that the combined stimulation of subthalamic nucleus and substantia nigra pars reticulata improves axial symptoms compared with standard subthalamic nucleus stimulation. Twelve patients were enrolled in this 2 × 2 cross-over double-blind randomized controlled clinical trial and both the safety and efficacy of combined subthalamic nucleus and substantia nigra pars reticulata stimulation were evaluated compared with standard subthalamic nucleus stimulation. The primary outcome measure was the change of a broad-scaled cumulative axial Unified Parkinson’s Disease Rating Scale score (Scale II items 13–15, Scale III items 27–31) at ‘3-week follow-up’. Secondary outcome measures specifically addressed freezing of gait, balance, quality of life, non-motor symptoms and neuropsychiatric symptoms. For the primary outcome measure no statistically significant improvement was observed for combined subthalamic nucleus and substantia nigra pars reticulata stimulation at the ‘3-week follow-up’. The secondary endpoints, however, revealed that the combined stimulation of subthalamic nucleus and substantia nigra pars reticulata might specifically improve freezing of gait, whereas balance impairment remained unchanged. The combined stimulation of subthalamic nucleus and substantia nigra pars reticulata was safe, and of note, no clinically relevant neuropsychiatric adverse effect was observed. Patients treated with subthalamic nucleus and substantia nigra pars reticulata stimulation revealed no ‘global’ effect on axial motor domains. However, this study opens the perspective that concomittant stimulation of the substantia nigra pars reticulata possibly improves otherwise resistant freezing of gait and, therefore, highly warrants a subsequent phase III randomized controlled trial.

Establishing equivalence or non-inferiority in clinical trials: part 20 of a series on evaluation of scientific publications

BACKGROUND

An increasing number of clinical trials are being performed to show the absence of relevant differences between the effects of two treatments. The primary care physician makes use of the results of so-called equivalence studies, at least indirectly, practically every day. Equally important are active control clinical trials in which the efficacy of a new treatment has to be proven through demonstrating non-inferiority as compared to a standard treatment.

METHODS

Explanation of basic principles and statistical techniques with reference to the original literature; selective searches in the medical literature.

RESULTS

First of all, a suitable distributional parameter must be chosen that can be considered a reasonable measure of dissimilarity of the population effects of the treatments under comparison. The simplest approach to the statistical demonstration of equivalence or non-inferiority is to calculate confidence intervals for that parameter. To keep the required number of subjects for equivalence and non-inferiority studies as low as possible, statistical tests should be used which are optimized with respect to power.

CONCLUSION

Data from equivalence and non-inferiority studies need to be assessed for statistical significance no less than data that are generated to show that two treatments have different effects. A negative result in a traditional two-sided test does not suffice for statistically proving equivalence.