Single-site trials

There are other trial design concepts for you to be aware of. A clinical trial can be carried out at a single site or it can be a multi-center trial. In a single-site trial all of the patients are seen at the same clinical site, and in a multi-center trial several clinical sites are used. Multi-center trials are needed sometimes to eliminate site-specific bias or because there are more patients required than a single site can enroll. 

The number of study sites to be used for a clinical trial depends on the characteristics and number of subjects that need to be recruited. Often, a sufficient number of participants cannot be enrolled from a single site, especially if the study inclusion criteria are restrictive and the timeframe for recruitment is limited. In order to complete the study within a reasonable period of time, an inclusion of multiple research centers is often necessary (Chow and Liu, 1998). The selection of study sites depends on several factors including ... 

A single field trial is all that is required to provide the data necessary to establish a tolerance for the processed commodities identified in OPPTS 860.1520. However, one may choose to conduct more than one field trial as insurance against crop failure at a single location which could delay a registration package submittal for another growing season (which would be far more costly to a business than the cost of multiple field trials). Once samples have been collected at one site, other trials could be terminated to minimize overall study cost. 

Site management organizations provide physician investigators, qualified patients, and support personnel for inpatient and outpatient clinical trials for single site or multicenter clinical trials. These firms provide services to sponsors and CROs. They are included in the CRO industry revenue totals, and unlike CROs they incorporate per pahent grant funds in their revenues. 

Category 4 vendors are sole-source API manufactures. First-time clinical trial supply manufacturers, offshore single pivotal trial clinical sites, and... 

The authors may well be correct when concluding that the surprising weakness of inhibition by aromatics results from slow desorption of a product. However, their model and rate equation appear questionable. Like aromatics, hydrogen is also strongly adsorbed, and so is as likely a candidate as toluene for accumulation on the surface. Also, a single-site mechanism is quite improbable with two strongly adsorbed products. Moreover, the "initial" rates were measured at conversions that entailed a decrease of up to 13% in fluid density, an effect not corrected for. Lastly, the trial equation was derived only from rates at low conversion and cannot be relied upon to reflect the behavior of the reaction as it progresses. 

Finally, we should make some remarks about the choice of the underlying Markov matrix. There are two general types of trial moves Glauber-like excitations [13], which change a single-site property and Kawasaki-like excitations [14], which are caused by a two-site exchange of a single-site property. Combinations of different moves of the same class or of... 

Bailin SJ. Is Bachmann s Bundle the only right site for single-site pacing to prevent atrial fibrillation Results of a multicenter randomized trial. Card Electrophysiol Rev 2003 7 325-8. 

The Interventional Management of Stroke (IMS I) Study was a multicenter, open-labeled, single-arm pilot study in which 80 patients (median NIHSS 18) were enrolled to receive IV rt-PA (0.6 mg/kg, 60 mg maximum, 15% of the dose as a bolus with the remainder administered over 30 minutes) within 3 hours of stroke onset (median time to initiation 140 minutes). " Additional rt-PA was subsequently administered via a microcatheter at the site of the thrombus in 62 of the 80 patients, up to a total dose of 22 mg over 2 hours of infusion or until complete recanalization. Primary comparisons were with similar subsets of the placebo and rt-PA-treated subjects from the NINDS rt-PA Stroke Trial. The 3-month mortality in IMS I subjects (16%) was numerically lower but not statistically different than the mortality of the placebo (24%) or rt-PA-treated subjects (21%) in the NINDS rt-PA Stroke Trial. The rate of symptomatic ICH (6.3%) in IMS I subjects was similar to that of the rt-PA-treated subjects (6.6%) but higher than the rate in the... 

The MERCI trial was a prospective single-arm, multicenter trial designed to test the safety and efficacy of the MERCI clot retrieval device to restore the patency of intracranial arteries in the first 8 hours of an acute stroke. All patients were ineligible for IV rt-PA. The occlusion sites were the intracranial vertebral artery, basilar... 

For applications made in the glasshouses or from post-harvest treatments, a single season is usually adequate since the geographical distribution of trial sites is immaterial. Specific conditions which affect cultivation (heated glasshouse, cold glasshouse, hydroponics) should be considered. These climatic conditions in protected crops usually lead to higher residues compared with the open-field situations. 

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