A difficult question about crossover randomised trials

[lovebird]

A randomized, double-blind, crossover study of the effects of long-term treatment with Salmeterol on asthma control was carried out (Wilding P et al. BMJ 1997; 314: 1441-1446). 101 subjects with mild or moderate asthma taking at least 200 micrograms twice daily of beclomethasone dipropionate or buclesonide were included. Patients continued to take this medication but were randomized to receive additionally either Salmeterol 50 micrograms twice daily or placebo for a six month period, with a one month washout between the two. The primary outcomes of the trial were a reduction in inhaled steroid use, exacerbations of asthma and the use of oral steroids.
Select all of the following statements which you believe to be true.

Patients in the study received treatment with either salmeterol or placebo only.
The washout period allowed patients to have a break from all therapy.
A cross-over study design meant that each patient was used as his/her own control.
The cross-over nature of this study meant that more patients had to be recruited.
When the statistical analysis was performed, the responses for all patients whilst on salmeterol were compared to the responses for all patients whilst on placebo.

Hi everyone.

Having problems with the above question and would appreciate any help. I think the first statement is wrong as patients would have had both the salmeterol and the placebo (or vice versa).

The washout period presumably applied only to the salmeterol/placebo and not to other drugs.

I think the third was true.

The fourth is no.

Don't understand what the final question is about. Finding the wording very difficult. 3 and 5 cannot both be true.

BW

Lovebird

[Prometheus]

You've basically answered it. I think question 5 is asking whether the analysis took global statistics for the 'active' and 'placebo' group. But if they did this there would be no point implementing a cross-over trial. Elaborating your answer to question 3 should lead you to the answer to five properly: they follow as you already suspect.