Validation and use of a parametric model for projecting cystic fibrosis survivorship beyond observed data: a birth cohort analysis

Abstract

BackgroundThe current lifetable approach to survival estimation is favoured by CF registries. Recognising the limitation of this approach, we examined the utility of a parametric survival model to project birth cohort survival estimates beyond the follow-up period, where short duration of follow-up meant median survival estimates were indeterminable.MethodsParametric models were fitted to observed survivorship data from the US CF Foundation (CFF) Patient Registry 1980–1994 birth cohort. Model-predicted median survival was estimated. The best fitting model was applied to a Cystic Fibrosis Registry of Ireland dataset to allow an evaluation of the model's ability to estimate predicted median survival. This involved a comparison of birth cohort lifetable predicted and observed (Kaplan–Meier) median survival estimates.ResultsA Weibull model with main effects of gender and birth cohort was developed using a US CFF dataset (n=13 115) for which median survival was not directly estimable. Birth cohort lifetable predicted median survival for male and female patients born between 1985 and 1994 and surviving their first birthday was 50.9 and 42.4 years respectively. To evaluate the accuracy of a Weibull model in predicting median survival, a model was developed for the 1980–1984 Cystic Fibrosis Registry of Ireland birth cohort (n=243), which had an observed (Kaplan–Meier) median survival of 27.7 years. Model-predicted median survival estimates were calculated using data censored at different follow-up periods. The estimates converged to the true value as length of follow-up increased.ConclusionsAccurate prognostic information that is clinically critical for care of patients affected by rare, life-limiting disorders can be provided by parametric survival models. Problems associated with short duration of follow-up for recent birth cohorts can be overcome using this approach, providing better opportunities to monitor survival and plan services locally.

Long noncoding RNA are aberrantly expressed in vivo in the cystic fibrosis bronchial epithelium

“…Females with CF have poorer lung function, higher mortality, earlier colonisation with Pseudomonas aeruginosa, and deteriorate with Burkholderia earlier than their male counterparts (Block et al, 2006, Corey et al, 1997, Rosenfeld et al, 1997, Demko et al, 1995, Jackson et al, 2011a, Jackson et al, 2011b. Recent work has focused on the role of steroid sex hormones such as estrogens in this "gender gap" (Chotirmall et al, 2010, Chotirmall et al, 2012a and has been reviewed elsewhere (Chotirmall et al, 2012b, Saint-Criq and Harvey, 2013, Sweezey and Ratjen, 2013.…”

Effect of Estrogen on Pseudomonas Mucoidy and Exacerbations in Cystic Fibrosis

“…[5][6][7] The Republic of Ireland has the highest incidence and carrier rate of cystic fibrosis worldwide 8 and a survival disadvantage for women. 9 Patients with cystic fibrosis become colonized and infected with nonmucoid P. aeruginosa; these strains convert to mucoid strains, on average, at a younger age in women than in men. 3,10,11 In an attempt to explain these observations, we and others have investigated the effect of the female sex hormone estradiol on airway biology.…”

An overview of international literature from cystic fibrosis registries. Part 4: Update 2011

“…Data from US CFF and Irish Registries were used by Jackson et al in 2 studies [12,13]. The 1st study [12] compared median predicted survival (MPS) and median age at death (MAD) in CF patients from the US and the Republic of Ireland (RoI), with the aim of evaluating whether these two parameters were good measures of CF survival and a useful way to compare small registries with large ones.…”