Researchers assessed the effects of continuous positive airway pressure on blood pressure in patients with moderate to severe obstructive sleep apnoea and recently diagnosed but untreated systemic hypertension. Blood pressure was measured using 24 hour ambulatory monitoring. A double blind randomized controlled trial study design was used. Control treatment was sham continuous positive airway pressure delivered at a very low pressure. A total of 169 patients were assigned to continuous positive airway pressure and 171 to sham treatment.
The primary outcome was the change at three months from baseline in mean 24 hour ambulatory blood pressure monitoring values. The analysis was undertaken by the principle of intention to treat. Continuous positive airway pressure was associated with a statistically significant reduction in blood pressure in patients with systemic hypertension and obstructive sleep apnoea.
Which one of the following statements best describes the principle of intention to treat analysis?
a) Patients are included in the analysis only if they intend to be treated after randomisation
b) Two groups of patients are compared on the basis of the treatment they eventually receive
c) Two groups of patients are compared on the basis of the treatment they were originally allocated
d) Participants are included in the analysis only if they complete the treatment originally allocated
e) Patients are included in the analysis only if they start the treatment allocated after randomisation