A new study attempts to evaluate the benefits of regular exercise in preventing depression compared with unmodified lifestyle in a sample of 80 healthy elderly men.
Which of the following is not possible in such a study design?
D. Blinding reduces differential assessment of outcomes of interest (ascertainment bias, information bias, or observer bias) that can occur if the investigator or participant is aware of the group assignment. Blinding can also improve compliance and retention of trial participants and reduce unaccounted supplemental care or treatment that may be sought by the participants. Single blinding refers to either the investigator or the patient being blind to group assignment. Double blinding refers to both the patient and the investigator remaining unaware of the group assignment after randomization. This is desirable but not always possible in RCTs. In the example above, the subjects who undertake the exercise schedule cannot be kept unaware of exercising! A single-blind trial is possible in such cases.
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When searching medical databases, the term MeSH refers to:
C. MeSH stands for medical subject headings. It is a thesaurus embedded in the Pubmed–Medline interface and can be used to search literature more effectively using recognized key words.
Which of the following is strictly correct about a single-blind study design?
E. Single blind: either the patient or the clinician remains unaware of the intervention given. Double blind: both the patient and investigator are unaware of the given intervention. Open label: both researchers and the participants are aware of treatment being given after randomization. Triple blind: apart from the patient and the researcher, those who measure the study outcomes (the assessors) are also unaware of the given intervention.
Which one of the following correctly describes a crossover trial?
B. If random interchange between treatment and placebo groups occurs halfway through the study, this will lead to chaos and failed randomization. This is termed as contamination. This can occur when participants or their care givers discover they are ‘controls’, and obtain the experimental treatment outside the trial, thus effectively becoming the active treatment group. Choice C is practically impossible; to share controls of one RCT with another means the trial is open label. When each subject in the trial receives both intervention and placebo with a washout period in between while remaining blind to the intervention, this is called as crossover RCT. Crossover trials are possible only if short-term outcomes are evaluated in chronic diseases. This is because the disease process must be sufficiently long for the subject to receive both interventions across its course. Any intervention applied in a crossover setting must not permanently alter the disease process.
A study evaluates the effect of various psychological interventions on bulimia.
This study could be termed as a factorial design if:
D. If one wishes to compare the effect of more than one intervention against placebo either a multi-arm RCT or a factorial design can be chosen. A multi-arm Randomized Controlled Trial (RCT) is a simple extension of the usual RCTs where an extra arm of subjects is generated through randomization to allocate the second intervention in addition to placebo and the first intervention groups. A factorial RCT evaluates the effect of more than one intervention, independently and also in combination. In the above example the effect of two different psychotherapies independently and in combination could be studied using a factorial design.
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