Researchers investigated whether specialist nurse intervention reduced morbidity and mortality in patients with chronic heart failure. A randomised controlled trial study design was used. The intervention consisted of specialist nurse home visits in addition to routine care. The aim of the intervention was to educate patients about heart failure and its treatment. The control treatment consisted of routine care alone, with patients managed as usual by the admitting physician and, subsequently, general practitioner. Participants were 165 patients admitted to an acute medical admissions unit with heart failure as a result of left ventricular systolic dysfunction. The intervention started before discharge and continued for up to one year. 1
The primary endpoint was a composite of death from all causes or first readmission to hospital with worsening heart failure. The Kaplan-Meier survival curves for the length of time after randomisation until occurrence of the primary endpoint were presented for the intervention and control treatment groups (figure). There was a significant difference in survival times between the treatment groups (log rank test P=0.033). The Kaplan-Meier survival probability estimates at 12 months were about 0.59 for intervention and 0.43 for control.
The researchers concluded that specially trained nurses can improve the morbidity and mortality of patients admitted to hospital with chronic heart failure.
Which of the following statements, if any, can be inferred?
a) About 43% of the control group had not experienced the primary endpoint by the end of the 12 month follow-up
b) For the intervention group, the probability of experiencing the primary endpoint some time after 12 months was about 0.59
c) For any patient, the time taken to experience the primary endpoint after starting treatment would have been longer if he or she had received the intervention rather than the control treatment
Statement b can be inferred, whereas a and c cannot.