What values of FEV1 are considered 'normal' and how does this change with age?
What values of FEV1 classify moderate and severe asthma?
What is the expected drop-out rate in such studies (if known)?
How would the baseline change if not given the treatments?
What metric do the researchers propose using to measure the difference between treatments? ie. relative differences vs. absolute differences, percent changes etc.
For the FVC test, it is normally repeated several times on patient. Is it repeated immediately after the previous test, or followed at a different time of the day?
What difference is the researchers hoping to see?
What kind of treatment effect are the researchers anticipating?
What is the expected difference between the two proposed treatments? ie. the expected effect size and the expected variability around this measure.
Is the new treatment to be used for all kinds of asthma or just certain types (e.g., allergic, exercise-induced, etc) ? In the former case, are you considering dividing the ashtma patients by asthma-type?
In Analysing controlled trials with baseline and follow up measurements, it seems that linear regression does not fit the data well. Does this matter?
Are any measurements being taken (e.g., changes of weight, diet, blood pressure, self-report questionnaires) within the two-month intervals?
What kind of variables have been found to be confounding for testing asthma drugs in the past (e.g., age, gender, etc)?.
Is it necessary to consider other factors that may influence the result?
Except gender, are there any other factors that have impacts on FVC? Or in other words, What decides the difference of FVC between male and female?
Do we need a two-sided test? In order to detect a meaningful effect, how powerful should this study become?
What is the participation rate for source population?
How do you plan on recruiting participants? Is it possible that some participants will have something in common (e.g. two members of the same family)
Since FEV1 depends on multiple variables (e.g. age, sex, height) are the researchers planning to take these into account when they assign the two treatments?
What kind of blinding strategy should this study choose? (unblinded, single, double or triple?) And what kind of biases will this study deal with?
For trials of chronic conditions, the study time is normally very long. Is it necessary to measure several times during the study period?
To elaborate on Danny's drop-out question, do you know why participants drop out? (Is it random? Death? The treatment not working?) Do you expect the drop-out rate to be larger in one group than the other? Is there a certain period after which drop-out increases? (e.g. Christmas)
What are they planning to do in case of possible drop outs?
What is the anticipated non-compliance rate? Since treatments are self-administered regularly each day, some patients may forget to take treatments. How to solve this problem?
If patients are self-reporting how do the researchers expect to confirm reliability and validity of measurements?