Cluster randomized clinical trials in orthodontics: design, analysis and reporting issues

Cluster randomized trials (CRTs) use as the unit of randomization clusters, which are usually defined as a collection of individuals sharing some common characteristics. Common examples of clusters include entire dental practices, hospitals, schools, school classes, villages, and towns. Additionally, several measurements (repeated measurements) taken on the same individual at different time points are also considered to be clusters. In dentistry, CRTs are applicable as patients may be treated as clusters containing several individual teeth. CRTs require certain methodological procedures during sample calculation, randomization, data analysis, and reporting, which are often ignored in dental research publications. In general, due to similarity of the observations within clusters, each individual within a cluster provides less information compared with an individual in a non-clustered trial. Therefore, clustered designs require larger sample sizes compared with non-clustered randomized designs, and special statistical analyses that account for the fact that observations within clusters are correlated. It is the purpose of this article to highlight with relevant examples the important methodological characteristics of cluster randomized designs as they may be applied in orthodontics and to explain the problems that may arise if clustered observations are erroneously treated and analysed as independent (non-clustered).

Readaptation of the peritoneum following extended pelvic lymphadenectomy and cystectomy has a significant beneficial impact on early postoperative recovery and complications: results of a prospective randomized trial

Prolonged postoperative pain and delayed intestinal transit are frequent problems following extended pelvic lymph-node dissection (PLND) and cystectomy.

A randomized trial of effects of health risk appraisal combined with group sessions or home visits on preventive behaviors in older adults

Background. To explore effects of a health risk appraisal for older people (HRA-O) program with reinforcement, we conducted a randomized controlled trial in 21 general practices in Hamburg, Germany. Methods. Overall, 2,580 older patients of 14 general practitioners trained in reinforcing recommendations related to HRA-O-identified risk factors were randomized into intervention (n = 878) and control (n = 1,702) groups. Patients (n = 746) of seven additional matched general practitioners who did not receive this training served as a comparison group. Patients allocated to the intervention group, and their general practitioners, received computer-tailored written recommendations, and patients were offered the choice between interdisciplinary group sessions (geriatrician, physiotherapist, social worker, and nutritionist) and home visits (nurse). Results. Among the intervention group, 580 (66%) persons made use of personal reinforcement (group sessions: 503 [87%], home visits: 77 [13%]). At 1-year follow-up, persons in the intervention group had higher use of preventive services (eg, influenza vaccinations, adjusted odds ratio 1.7; 95% confidence interval 1.4–2.1) and more favorable health behavior (eg, high fruit/fiber intake, odds ratio 2.0; 95% confidence interval 1.6–2.6), as compared with controls. Comparisons between intervention and comparison group data revealed similar effects, suggesting that physician training alone had no effect. Subgroup analyses indicated favorable effects for HRA-O with personal reinforcement, but not for HRA-O without reinforcement. Conclusions. HRA-O combined with physician training and personal reinforcement had favorable effects on preventive care use and health behavior.

Randomized trial of a computerized coronary heart disease risk assessment tool in HIV-infected patients receiving combination antiretroviral therapy

Exposure to combination antiretroviral therapy (cART) can lead to important metabolic changes and increased risk of coronary heart disease (CHD). Computerized clinical decision support systems have been advocated to improve the management of patients at risk for CHD but it is unclear whether such systems reduce patients' risk for CHD.

Randomized trial comparing the i-gel™ and Magill tracheal tube with the single-use ILMA™ and ILMA™ tracheal tube for fibreoptic-guided intubation in anaesthetized patients with a predicted difficult airway

The i-gel™ is a single-use supraglottic airway device (SAD) that allows fibreoptic-guided tracheal intubation through the device. Until now, no prospective data for this procedure are available. Therefore, in a prospective randomized controlled trial, we evaluated fibreoptic-guided tracheal intubation with a standard Rüsch™ PVC tracheal tube (TT) through the i-gel™ compared with the single-use ILMA™ (sILMA™) TT through the sILMA™ in patients with a predicted difficult airway.

Cognitive function in postmenopausal women receiving adjuvant letrozole or tamoxifen for breast cancer in the BIG 1-98 randomized trial

Cognitive function in postmenopausal women receiving letrozole or tamoxifen as adjuvant endocrine treatment was compared during the fifth year of treatment in a substudy of the BIG 1-98 trial. In BIG 1-98 patients were randomized to receive adjuvant (A) 5-years tamoxifen, (B) 5-years letrozole, (C) 2-years tamoxifen followed by 3-years letrozole, or (D) 2-years letrozole followed by 3-years tamoxifen. The primary comparison was the difference in composite score for patients taking letrozole (B+C; N=65) vs. tamoxifen (A+D; N=55). The patients taking letrozole had better overall cognitive function than those taking tamoxifen (difference in mean composite z-scores=0.28, P=0.04, 95% CI: 0.02, 0.54, Cohen's D=0.40 indicating small to moderate effect). In this substudy, breast cancer patients taking adjuvant letrozole during the fifth year of treatment had better cognitive function than those taking tamoxifen, suggesting aromatase inhibitors do not adversely impact cognition compared with tamoxifen.

Prospective randomized trial comparing sutured with sutureless mesh fixation for Lichtenstein hernia repair: long-term results

Following Lichtenstein hernia repair, up to 25% of patients experience prolonged postoperative and chronic pain as well as discomfort in the groin. One of the underlying causes of these complaints are the compression or irritation of nerves by the sutures used to fixate the mesh. We compared the level and rate of chronic pain in patients operated with the classical Lichtenstein technique fixated by sutures to patients with sutureless mesh fixation technique.

A randomized trial for the treatment of refractory status epilepticus

Refractory status epilepticus (RSE) has a mortality of 16-39%; coma induction is advocated for its management, but no comparative study has been performed. We aimed to assess the effectiveness (RSE control, adverse events) of the first course of propofol versus barbiturates in the treatment of RSE.

Clinical and microbiologic results 12 months after scaling and root planing with different irrigation solutions in patients with moderate chronic periodontitis: a pilot randomized trial

The aim of this study is to determine in a randomized trial the impact on treatment outcome after 12 months of different subgingival irrigation solutions during scaling and root planing (SRP).

Effect of biolimus-eluting stents with biodegradable polymer vs bare-metal stents on cardiovascular events among patients with acute myocardial infarction: the COMFORTABLE AMI randomized trial

The efficacy and safety of drug-eluting stents compared with bare-metal stents remains controversial in patients with ST-segment elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PCI).