Predicting survival in end-stage cystic fibrosis

The natural history of cystic fibrosis (CF) is unpredictable and the optimal timing for lung transplantation in end-stage disease uncertain. Predicting survival based on FEV1 alone remains controversial and therefore the aim of this study was to assess the value of walk test performance in pre-transplant assessment. Retrospective review of adult patients with end-stage CF who underwent transplant assessment between 1988 and 2004 including a documented walk test on room air, but who died before transplant. The six-minute walk test (6MWT) was used between 1988 and 1993 and the shuttle walk test (SWT) thereafter, the two cohorts were therefore individually assessed. A total of 121 patients were identified. The median (IQR) survival in patients performing SWT (n=77) and 6MWT (n=44) was 363 days (226, 566) and 433 days (232, 844), respectively, with survival in both cohorts significantly associated with pre-test (resting) heart rate (HR) (p<0.03), but not distance walked, pre-test SpO2, FEV1 or BMI. It was predicted that 85% of patients performing SWT with a resting HR of 120 bpm, 70% of those with a HR of 109 bpm (cohort median) but only 25% with a HR of 72 bpm would die within 500 days. Distance walked in the SWT was significantly related to pre-test HR (p<0.01), SpO2 (p<0.01) and Borg score (p=0.016) when performing linear regression. Only pre-test HR remained significant when performing multiple regression. Resting heart rate was the only consistent parameter in this study at predicting a high risk of dying on the transplant waiting list.