Endgames Statistical Question

Kaplan-Meier survival curves: interpretation and communication of risk

BMJ 2013; 347 doi: http://dx.doi.org/10.1136/bmj.f7118 (Published 29 November 2013) Cite this as: BMJ 2013;347:f7118
  1. Philip Sedgwick, reader in medical statistics and medical education,
  2. Katherine Joekes, senior lecturer in clinical communication
  1. 1Centre for Medical and Healthcare Education, St George’s, University of London, London, UK
  1. p.sedgwick{at}sgul.ac.uk

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.

Kaplan-Meier survival curves for length of time after randomisation until occurrence of the primary endpoint (death from any cause or hospital readmission for heart failure) for the intervention and control treatment groups. The numbers of patients still at risk of experiencing the primary endpoint are indicated

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 …

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