Please only answer this question if you have epidemiology experience. A randomiz
ID: 12701 • Letter: P
Question
Please only answer this question if you have epidemiology experience.A randomized, double-blind, placebo-controlled clinical trial is being conducted to determine whether a virus can be used to attack the plaques in the brain that are associated with Alzheimer's Disease. Three hundred patients were randomized in equal numbers to the treatment or placebo. After a two-year period, 25% of patients receiving the treatment and 10% of controls exhibited clinical improvements. Serious adverse effects occurred among 10% of those treated with the virus and 22% of controls.
The similarity of treatment groups with respect to baseline characteristics most likely occurred because of:
Answer
1. Blinding
2. Placebo Effect
3. Healthy Worker Effect
4. Randomization
5. Informed Consent
Explanation / Answer
I have a master's in public health, so yes I have epi experience.
It would be helpful if you can clarify the question. So the treatment groups are similar in baseline traits... does this refer to the virus treatment group vs. placebo? Or are there multiple virus treatment groups??
And by "similarity of treatment groups with respect to baseline characteristics" I assume you are referring to the idea that the control & treatment groups matched in basic traits such as age, height, weight, gender, etc. Or are you referring to something you didn't mention above...ie that the outcomes for the treatment group and placebo group were similar (your data says they weren't)?
Blinding (neither control, treatment, or researchers know who gets placebo vs. drug) isn't going to produce any changes in sample group baseline characteristics. The placebo effect is simply the tendancy of people to exhibit symptomatic improvement when they think they're getting a treatment. All subjects must complete an informed consent statement indicating that they are freely participating in the study and understand the procedures, risks, etc.
Regardless, the answer here is most likely randomization. The similarity in Tx groups regarding baseline traits (ie subjects have same avg proportions of gender, age, race, etc) is a fundamental goal of the randomization process and indicates well constructed sample groups which are randomly divided across all the groups.
The healthy worker bias occurs because people who are more concerned about their health tend to enroll in these clinical trials, making it more likely that the sample group will not reflect the general population; ie bias. This would produce similarity in baseline health levels and people in the sample groups would all have similar health characteristics, but not necessarily age/gender/race etc.