Investigators must employ high ethical stand ards to ensure that enrollees know how the trial works, the chances of receiving active therapy as opposed to a placebo, the expected outcomes, and what risks and complications the participants may experience. These stand ards are needed to protect enrollees, esp. those with chronic, poorly controlled, or potentially fatal illnesses from assuming that participation in an experiment guarantees an imminent cure. Participation in the experiment does not guarantee a cure. In many instances trials prove that the intervention tested does not work; in some, that the intervention is hazardous; and , only in a few, that the intervention is as good as doing nothing or as good as the best available contemporary therapy. Even when clinical outcomes are not positive, a trial usually illuminates some elements of pharmacology or pathophysiology that may be used in furthering the understand ing of an illness. Many human drug trials, esp. trials of new treatments for cancer, are conducted in four phases, three of them before approval for general use. An increasingly larger number of participants are enrolled for each successive phase.

crossover t.A scientific study of a therapeutic agent in which participants are exposed in sequence to the putative cure and subsequently (or previously) to an inactive agent or an agent whose efficacy has been previously established. The participants cross over from one arm of the study to the other and serve as their own control group.

Participants in such trials are usually under the care of a team of physicians and nurses and are closely monitored, often with testing and examinations on a weekly basis. The clinical trial nurse or nurse research specialist has a broad variety of roles, depending on the nature of the investigation. The roles include recruiting and introducing patients to the trial, coordinating their care, gathering data about side effects and tolerance, and , frequently, serving as a principal or collaborative investigator. Trial planning and design, data interpretation and analysis, and assessments of toxicity are all elements of the work. Health insurers and managed care providers may place restrictions on clinical trial coverage. Many states have laws requiring insurers to pay for the routine costs of all or some clinical trials. Patient advocates work with researchers to make sure a clinical trial is relevant, as safe as possible, and accessible to the broadest variety of patients.

equivalence t.A rand omized clinical trial in which two distinct agents are compared with each other and sometimes with an inert agent (a placebo) as well. If two agents work equally well, the less expensive, better tolerated, or more easily administered one may be preferred.

negative t.Negative study.

noninferiority t.A study to determine if a treatment is no worse than the currently accepted therapy.

observational t.Observational study.

parallel t.A research study in which groups of patients are followed for the same time but are given different treatments; e.g., one group may receive an inactive substance while another is treated with a drug whose effectiveness must be determined. The impact of the drug can thus be compared with the placebo at varying times, such as 4 weeks, 4 months, or 4 years after the study begins.

PEEP decrement t.Sequential decreases in positive end-expiratory pressures (PEEP) until the lowest level of PEEP is achieved that improves lung compliance the most, without reducing the patient's partial pressure of oxygen. PEEP is then adjusted to a value just higher than that value.

phase I t.

Variant: phase 1 trial

A clinical trial to determine the toxicity of a new drug. Such trials test safety and maximum dosage, help researchers discover the best way to administer a treatment (orally or intravenously) and the most appropriate dosage. Phase I trials also help to discover potentially harmful adverse effects of a new treatment. Even though the trial is not designed to show whether the treatment is effective, since an experimental drug is chosen for its promise, the patient may still benefit. Only a small number of patients are included (15 to 25 who have not been helped by other treatments), and there usually is no control group.

phase II t.

Variant: phase 2 trial

A clinical trial to determine the potential effectiveness of a new drug. Generally, if at least 20% of the study subjects respond positively to it, e.g., achieve a 50% reduction in the total size of their measurable tumor, the new therapy will receive further testing. Another crucial statistic is the duration of response. Short-term responses may mean little in terms of survival; long-term responses indicate that the drug is benefiting some patients.

phase III t.

Variant: phase 3 trial

A clinical trial to explore the clinical use of a new drug, esp. relative to other known effective agents (the current stand ard of care). These trials often include thousand s of enrollee patients. By law, all such patients receive real treatment; no placebos are given. But the trial is usually double-blinded, with patients divided rand omly into two groups: an experimental group and a control group on stand ard treatment, with neither patients nor researchers knowing to which group the patient belongs.

phase IV t.

Variant: phase 4 trial

A clinical trial to examine long-term effectiveness and adverse effects that might occur from a treatment after the Food and Drug Administration has approved its use by the public. Such trials, involving thousand s or tens of thousand s of enrollee patients, are either mand ated by regulatory authorities or undertaken voluntarily by a pharmaceutical manufacturer once the drug has gone to market. Often it is only in Phase IV trials that especially rare adverse effects emerge. Enrollee patients in a clinical trial should have the approval of their personal oncologist, and they should seek a second opinion (which is covered by insurance) to obtain more input on what trials to consider.

platform t.A clinical trial in which multiple interventions are tested simultaneously, with some interventions discarded and some interventions recruited, depending on their performance as the trial proceeds.

pragmatic t.A trial to evaluate the effectiveness of a treatment investigated under real-world conditions, rather than during the application of stringent exclusion criteria.

rand omized controlled t.

ABBR: RCT

An experimental study to assess the effects of a particular variable, e.g., a drug or treatment, in which subjects are assigned rand omly to an experimental, placebo, or control group. The experimental group receives the drug or procedure; the placebo group's medication is disguised to resemble the drug being investigated. The control group receives nothing. Members of each group are prevented from knowing whether they are receiving active therapy. The researchers gathering the data are also typically blinded to group assignment.

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Although RCTs are an essential element in proving clinical relationships (such as between the use of a new drug and the safe cure of a disease), most RCTs do not enroll enough patients for a long enough time to detect rare events.

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spontaneous breathing t.Spontaneous breathing test.

superiority t.A study that directly compares two treatments to see which of them achieves better results.