Triple-blind Trial: From 1 Different Sources
See “blinding”.
A controlled research study of the safety and effectiveness of drugs, devices or techniques that occurs in four phases, starting with the enrolment of a small number of people, to the later stages in which thousands of people are involved prior to approval by the licensing authorities (for example, the Food and Drug Administration).... clinical trial
A disorder in which abnormal FAECES occur as a result of a redundant loop in the small INTESTINE. The loop obstructs the normal ?ow of the contents of the bowel, causing stagnation. The syndrome is characterised by light-yellow, smelly, fatty, bulky faeces. The patient suffers from tiredness, malaise and loss of weight. Previous abdominal surgery is sometimes the cause, but the condition can be inherited. Blockage of intestinal contents upsets the bowel’s normal bacterial balance and hinders the normal absorption of nutrients. Treatment is either with antibiotics or, if that fails, surgery.... blind loop syndrome
A scienti?c study in which di?erent patients receive a di?erent drug, the same drug at a different dose, or a placebo – with neither the investigators assessing the outcome nor the subjects being treated knowing which of these the latter are receiving. The aim is to remove any hint of bias due to the investigators’ or patients’ preferences or preconceptions. The results are analysed after all the data have been collected and the code has been broken. Trials should have a separate supervising committee, the members of which know the code but do not take part in the study. Their job is to check the results at intervals so they can stop the trial if one arm of treatment is clearly better than another. Otherwise, it would be unethical to continue. (See INTERVENTION STUDY.)... double blind trial
Also known as DPT vaccine, this is an injection that provides IMMUNITY against DIPHTHERIA, pertussis (whooping-cough) and TETANUS. It is given as a course of three injections at around the ages of two, three and four months. A booster dose of diphtheria and tetanus is given at primary-school age. Certain infants – those with a family history of EPILEPSY, or who have neurological disorders or who have reacted severely to the ?rst dose – should not have the pertussis element of DPT. (See MMR VACCINE; IMMUNISATION.)... triple vaccine
(See EVIDENCE-BASED MEDICINE.) Clinical trials aim to evaluate the relative effects of di?erent health-care interventions. They are based on the idea that there must a fair comparison of the alternatives in order to know which is better. Threats to a fair comparison include the play of chance and bias, both of which can cause people to draw the wrong conclusions about how e?ective a treatment or procedure is.
An appreciation of the need to account for chance and bias has led to development of methods where new treatments are compared to either a PLACEBO or to the standard treatment (or both) in a controlled, randomised clinical trial. ‘Controlled’ means that there is a comparison group of patients not receiving the test intervention, and ‘randomised’ implies that patients have been assigned to one or other treatment group entirely by chance and not because of their doctor’s preference. If possible, trials are ‘double-blind’ – that is, neither the patient nor the investigator knows who is receiving which intervention until after the trial is over. All such trials must follow proper ethical standards with the procedure fully explained to patients and their consent obtained.
The conduct, e?ectiveness and duplication of clinical trials have long been subjects of debate. Apart from occasional discoveries of deliberately fraudulent research (see RESEARCH FRAUD AND MISCONDUCT), the structure of some trials are unsatisfactory, statistical analyses are sometimes disputed and major problems have been the – usually unwitting – duplication of trials and non-publication of some trials, restricting access to their ?ndings. Duplication occurs because no formal international mechanism exists to enable research workers to discover whether a clinical trial they are planning is already underway elsewhere or has been completed but never published, perhaps because the results were negative, or no journal was willing to publish it, or the authors or funding authorities decided not to submit it for publication.
In the mid 1980s a proposal was made for an international register of clinical trials. In 1991 the NHS launched a research and development initiative and, liaising with the COCHRANE COLLABORATION, set out to collect systematically data from published randomised clinical trials. In 1994 the NHS set up a Centre for Reviews and Dissemination which, among other responsibilities, maintains a database of research reviews to provide NHS sta? with relevant information.
These e?orts are hampered by availability of information about trials in progress and unpublished completed trials. With a view to improving accessibility of relevant information, the publishers of Current Science, in 1998, launched an online metaregister of ongoing randomised controlled trials.
Subsequently, in October 1999, the editors of the British Medical Journal and the Lancet argued that the case for an international register of all clinical trials prior to their launch was unanswerable. ‘The public’, they said, ‘has the right to know what research is being funded. Researchers and research funders don’t want to waste resources repeating trials already underway.’ Given the widening recognition of the importance to patients and doctors of the practice of EVIDENCE-BASED MEDICINE, the easy availability of information on planned, ongoing and completed clinical trials is vital. The register was ?nally set up in 2005.... clinical trials
A trial in which each of the groups involved will receive each of the treatments, but in a randomized order: that is, they will start in one arm of the trial, but will deliberately ‘cross over’ to the other arm(s) in turn.... crossover trial
A method of comparing the results between two or more groups of patients intentionally subjected to di?erent methods of treatment – or sometimes of prevention. Those subjects entering the trial have to give their informed permission. They are allocated to their respective groups using random numbers, with one group (controls) receiving no active treatment, instead receiving either PLACEBO or a traditional treatment. Preferably, neither the subject nor the assessor should know which ‘regimen’ is allocated to which subject: this is known as a double-blind trial.... randomised controlled trial
See “blinding”.... single-blind trial
A test on human volunteers of the effectiveness and safety of a drug. A trial can also involve systematic comparison of alternative forms of medical or surgical treatment for a particular disorder. Patients involved in clinical trials have to give their consent, and the trials are approved and supervised by an ethics committee.... trial, clinical
(in Britain) an incomplete list of persons who are technically blind or partially sighted due to reduced visual acuity, or who have severely restricted fields of vision (see blindness). Registration is voluntary, but it is a precondition for the receipt of some financial benefits. The list is maintained by local authorities (England and Wales), regional or island councils (in Scotland), or the Health and Social Care Board (Northern Ireland).... blind and partially sighted register
see intervention study.... blind trial
see intervention study.... controlled trial
see intervention study.... cross-over trial
a histological stain consisting of water-soluble aniline blue or methyl blue, orange G, and oxalic acid. Before the stain is applied the tissue is mordanted, then treated with acid fuchsin and phosphomolybdic acid. Nuclei stain red, muscle red to orange, nervous tissue lilac, collagen dark blue, and mucus and connective tissue become blue. [F. B. Mallory]... mallory’s triple stain
see intervention study.... randomized controlled trial
see gallop rhythm.... triple rhythm
1. (in *prenatal screening) a blood test that can be performed between the 15th and 20th weeks of pregnancy but has largely been replaced by combined first-trimester *PAPP-A screening and *nuchal translucency scanning. Levels of *alpha-fetoprotein (AFP), *unconjugated oestriol (uE3), and *human chorionic gonadotrophin (hCG) in the serum are computed with maternal age to determine the statistical likelihood of the fetus being affected by Down’s syndrome or spina bifida. The double test is similar but omits measurement of uE3. 2. see insulin stress test.... triple test
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