Design effect in multicenter studies: gain or loss of power?

<p>Abstract</p> <p>Background</p> <p>In a multicenter trial, responses for subjects belonging to a common center are correlated. Such a clustering is usually assessed through the design effect, defined as a ratio of two variances. The aim of this work was to describe and understand situations where the design effect involves a gain or a loss of power.</p> <p>Methods</p> <p>We developed a design effect formula for a multicenter study aimed at testing the effect of a binary factor (which thus defines two groups) on a continuous outcome, and explored this design effect for several designs (from individually stratified randomized trials to cluster randomized trials, and for other designs such as matched pair designs or observational multicenter studies).</p> <p>Results</p> <p>The design effect depends on the intraclass correlation coefficient (ICC) (which assesses the correlation between data for two subjects from the same center) but also on a statistic <it>S</it>, which quantifies the heterogeneity of the group distributions among centers (thus the level of association between the binary factor and the center) and on the degree of global imbalance (the number of subjects are then different) between the two groups. This design effect may induce either a loss or a gain in power, depending on whether the <it>S </it>statistic is respectively higher or lower than 1.</p> <p>Conclusion</p> <p>We provided a global design effect formula applying for any multicenter study and allowing identifying factors – the ICC and the distribution of the group proportions among centers – that are associated with a gain or a loss of power in such studies.</p

Prevention of haematoma progression by tranexamic acid in intracerebral haemorrhage patients with and without spot sign on admission scan: a statistical analysis plan of a pre-specified sub-study of the TICH-2 trial

Objective We present the statistical analysis plan of a prespecified Tranexamic Acid for Hyperacute Primary Intracerebral Haemorrhage (TICH)-2 sub-study aiming to investigate, if tranexamic acid has a different effect in intracerebral haemorrhage patients with the spot sign on admission compared to spot sign negative patients. The TICH-2 trial recruited above 2000 participants with intracerebral haemorrhage arriving in hospital within 8 h after symptom onset. They were included irrespective of radiological signs of on-going haematoma expansion. Participants were randomised to tranexamic acid versus matching placebo. In this subgroup analysis, we will include all participants in TICH-2 with a computed tomography angiography on admission allowing adjudication of the participants’ spot sign status. Results Primary outcome will be the ability of tranexamic acid to limit absolute haematoma volume on computed tomography at 24 h (± 12 h) after randomisation among spot sign positive and spot sign negative participants, respectively. Within all outcome measures, the effect of tranexamic acid in spot sign positive/negative participants will be compared using tests of interaction. This sub-study will investigate the important clinical hypothesis that spot sign positive patients might benefit more from administration of tranexamic acid compared to spot sign negative patients

Hospital mortality of adults admitted to Intensive Care Units in hospitals with and without Intermediate Care Units: a multicentre European cohort study.

INTRODUCTION: The aim of the study was to assess whether adults admitted to hospitals with both Intensive Care Units (ICU) and Intermediate Care Units (IMCU) have lower in-hospital mortality than those admitted to ICUs without an IMCU. METHODS: An observational multinational cohort study performed on patients admitted to participating ICUs during a four-week period. IMCU was defined as any physically and administratively independent unit open 24 hours a day, seven days a week providing a level of care lower than an ICU but higher than a ward. Characteristics of hospitals, ICUs and patients admitted to study ICUs were recorded. The main outcome was all-cause in-hospital mortality until hospital discharge (censored at 90 days). RESULTS: One hundred and sixty-seven ICUs from 17 European countries enrolled 5,834 patients. Overall, 1,113 (19.1%) patients died in the ICU and 1,397 died in hospital, with a total of 1,397 (23.9%) deaths. The illness severity was higher for patients in ICUs with an IMCU (median Simplified Acute Physiology Score (SAPS) II: 37) than for patients in ICUs without an IMCU (median SAPS II: 29, P <0.001). After adjustment for patient characteristics at admission such as illness severity, and ICU and hospital characteristics, the odds ratio of mortality was 0.63 (95% CI 0.45 to 0.88, P = 0.007) in favour of the presence of IMCU. The protective effect of the IMCU was absent in patients who were admitted for basic observation, for example, after surgery (odds ratio 1.15, 95% CI 0.65 to 2.03, P = 0.630) but was strong in patients admitted to an ICU for other reasons (odds ratio 0.54, 95% CI 0.37 to 0.80, P = 0.002). CONCLUSIONS: The presence of an IMCU in the hospital is associated with significantly reduced adjusted hospital mortality for adults admitted to the ICU. This effect is relevant for the patients requiring full intensive treatment. TRIAL REGISTRATION: Clinicaltrials.gov NCT01422070. Registered 19 August 2011

Management of sacrococcygeal chordomas

A total of 16 patients in our clinic (six women, ten men; mean age 54.87 years, range 38–78 years) were diagnosed as having a sacrococcygeal chordoma. Pain was the presenting symptom in all patients. In five patients, the chordoma was inoperable. A total of 11 patients were followed-up for a mean period of 64.8 months (range 7–152 months). Five patients were lost to follow-up (3 in the operable group and two in the inoperable group). The three remaining inoperable patients received radiation therapy. The eight remaining operable patients underwent a total of 12 operations (four anterior and posterior, eight posterior only). Five of these patients received adjuvant radiotherapy and two patients received both radiotherapy and chemotherapy. In follow-up, eight patients had evidence of disease and one patient remained disease-free. Problems encountered during therapy and follow-up included urinary incontinence (72%), rectal incontinence (36%), wound infection (36%), and lower extremity muscle weakness (36%). Two patients died from metastases to the lung. Of the remaining nine patients, eight were ambulatory, with seven needing support to walk. One patient was unable to walk at all due to lower extremity muscle weakness

Ressecção de cordoma sacral com abaixamento de cólon: relato de caso Sacral chordoma resection with colo anal anastomosis: case report

O cordoma é uma lesão maligna da medula espinhal, que se origina nos remanescentes ectópicos de tecido notocordial. Trata-se de neoplasia rara e sua localização preferencial é o sacro. Tem crescimento lento, mas comportamento localmente agressivo. Relatamos um caso de ressecção de cordoma sacral com abaixamento de cólon. Para extirpação oncológica da lesão foi necessária a abordagem colorretal e ortopédica. Novas técnicas preconizando cirurgias mais agressivas melhoraram significativamente a expectativa de vida dos pacientes portadores de cordoma, bem como o tempo de vida livre de doença. Na busca dessa cirurgia oncológica ideal, a abordagem multidisciplinar é essencial.<br>Chordoma is a rare malignant lesion of spinal cord originated from ectopic remnants of notocordial tissue. Its presentation is characterized by slow growth in spite of locally aggressive behaviour. We report a case of multidisciplinary oncologic resection with coloanal anastomosis. Extended and aggressive resections improved significantly the disease free survival in patients with chordoma. The multidisciplinary oncologic approach is essential in order to reach this goal