Blind study
A blind study is a form of experiment in which the test subjects do not know whether they belong to the experimental or the control group. This eliminates the influence of expectations and behaviors that would be triggered by this information. Blind studies are particularly widespread in medical and psychological research ; see also ABX test .
medicine
Basics
In medical efficacy studies, people are exposed to either the treatment being tested or the control treatment during the course of a study. In drug studies, one speaks of verum or active substance (i.e. the drug to be examined) or control preparation (i.e. a drug to be compared or a placebo ). The verum and control preparation are referred to together as test preparations . The allocation of test treatment and control treatment is ideally done purely randomly ( randomized ) .
A study is open if the patients know whether they are getting the verum or the placebo. The study is against it
- single blind , if the patients do not know which substance (control or verum) they are receiving (test subject "blind"),
- double-blind if the patient and the treating physician do not know who is receiving which substance (test subject and test assistant "blind"),
- Triple blind if neither the patient, the attending physician nor those who carry out the evaluation know who is receiving which substance (test subject, test assistant and test evaluator “blind”). Only the person commissioning the study knows who received which substance.
Blinding techniques
In a blind study, it is important that the drugs cannot be distinguished from one another by the test persons. The drugs should look exactly the same (including the packaging), and smell and taste also play a role.
The double-dummy technique is used to compare medicinal products with very different appearances, such as different dosage forms . To do this, the test subjects must be given two drugs, one of which is a placebo. Example: A tablet is to be compared to a juice. The patients in one group receive the tablet with active ingredient and a placebo juice, the comparison group receives a placebo tablet and a juice with active ingredient.
Some drugs can be clearly recognized because of their typical properties (e.g. bitter taste) or side effects. In order to achieve reliable blinding here, active placebos would make sense for theoretical reasons, i.e. substances that only trigger the corresponding side effect. For ethical reasons, however, active placebos are rarely used.
Non-drug interventions can also be blinded. For example, there are special acupuncture needles in which the actual needle moves into a sheath after pressure and does not pierce the skin.
Scientific journals
In scientific journals, submitted research articles are usually not simply published, but go through an assessment process beforehand . Here it is customary to use a blind or double-blind report. The latter means that the authors do not know who the reviewers are, and the reviewers do not know who wrote the articles submitted to them. This is to prevent personal preferences or relationships between authors and reviewers from influencing the assessment of research contributions.
history
The history of the blind study is closely linked to that of the placebo . Placebos were first used in scientific medicine in the 17th century. The term "verum" (Latin for "the true, the right thing") for the actual drug comes from this time . During this period, the effectiveness of quinine in malarial fever was demonstrated by Thomas Sydenham (1624–1689). Quinine is therefore now considered to be the first verum preparation that has been proven not to be a placebo.
The British ship's doctor James Lind first introduced control medication in 1747. He tested the effectiveness of orange juice and lemon juice on two people suffering from scurvy . Lind believed that scurvy was a result of putrefaction in the body, which acids could prevent. That's why he experimented mainly with acidic food additives. For his experiment he divided twelve sailors suffering from scurvy into six groups. All received the same diet and the first group also received a quart (a liter) of cider daily. Group two took 25 drops of sulfuric acid , group three six spoons of vinegar , group four half a pint (almost a quarter liter) of sea water, group five two oranges and one lemon daily and the last group one spice paste and barley water . Treatment of group five had to be discontinued when the fruit ran out after six days, but by that point one of the sailors was already fit for duty and the other was almost recovered. In the other test participants, a certain effect of the treatment was only seen in the first group.
The first double-blind experiments in Central Europe began in the middle of the 19th century.
Individual evidence
- ^ I. Boutron, C. Estellat, L. Guittet et al .: Methods of Blinding in Reports of Randomized Controlled Trials Assessing Pharmacologic Treatments: A Systematic Review. In: PLoS Med . Volume 3, 2006. p. 425. doi : 10.1371 / journal.pmed.0030425
- ↑ FM Quitkin: placebos, Drug Effects, and Study Design: A Clinician's Guide. In: American Journal of Psychiatry. Volume 156, 1999. pp. 829-836.
- ↑ T. Gauler, T. Weihrauch: Placebo - an effective and harmless drug? Urban & Schwarzenberg Publishing House, 1997.
- ↑ A Treatise on the Scurvy. James Lind Initiative, the Royal College of Physicians of Edinburgh and Minervation. London 1753. Retrieved July 7, 2015.
- ^ U. Binz: The placebo phenomenon. Dissertation, University of Mannheim, 1977.