The objective of this study was to create a 5-year survivorship model to identify key clinical features of cystic fibrosis. Such a model could help researchers and clinicians to evaluate therapies, improve the design of prospective studies, monitor practice patterns, counsel individual patients, and determine the best candidates for lung transplantation. The authors used information from the Cystic Fibrosis Foundation Patient Registry (CFFPR), which has collected longitudinal data on approximately 90% of cystic fibrosis patients diagnosed in the United States since 1986. They developed multivariate logistic regression models by using data on 5,820 patients randomly selected from 11,630 in the CFFPR in 1993. Models were tested for goodness of fit and were validated for the remaining 5,810 patients for 1993. The validated 5-year survivorship model included age, forced expiratory volume in 1 second as a percentage of predicted normal, gender, weight-for-age z score, pancreatic sufficiency, diabetes mellitus, Staphylococcus aureus infection, Burkerholderia cepacia infection, and annual number of acute pulmonary exacerbations. The model provides insights into the complex nature of cystic fibrosis and supplies a rigorous tool for clinical practice and research.Keywords cystic fibrosis; logistic models; models, theoretical; multivariate analysis; proportional hazards models; survival analysis Cystic fibrosis is an autosomal recessive, multisystem disease leading to significant morbidity and early death. Since the disease was described in 1938 (1,2), treatments for its pancreatic and pulmonary manifestations have improved median survival in the United States from less than 6 months to about 32 years in 1998 (3). Severe pulmonary disease is the primary cause of cystic-fibrosis-related mortality, constituting 76.4 percent of such deaths in 1998 (3). Chronic inflammation and infection of the airways characterize cystic-fibrosis-related (4,5). Malnutrition, in part due to pancreatic insufficiency, was the major feature of the disease according to early reports, and it continues to be a substantial problem (1-3). With improved survival, additional manifestations such as diabetes mellitus have been recognized (6,7).Many studies have considered the survival effect of a variety of clinical and physiologic features of cystic fibrosis such as forced expiratory volume in 1 second as a percentage of predicted normal (FEV 1 %), gender, age, pregnancy, or particular therapies (4-26). We developed a single survivorship model that integrated many characteristics of cystic fibrosis and quantified the relative contribution of each.The current most commonly used survival model of cystic fibrosis was developed in 1992 and is based on FEV 1 % alone or on age, gender, and FEV 1 % (15). Clinicians often use this model to select patients to refer for lung transplantation. The model is relatively simple to use for estimating cystic fibrosis survival, but it has not been validated and does not incorporate clinical features of cystic fib...

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There is considerable variability in the clinical course of disease in cystic fibrosis (CF). Although currently unidentified modifier genes might explain some of this heterogeneity, other factors are probably contributory. Socioeconomic status (SES) is an important predictor of health status in many chronic polygenic diseases, but its role in CF has not been systematically evaluated. We performed a historical cohort analysis of pediatric CF patients in the United States using National Cystic Fibrosis Foundation Patient Registry (NCFPR) data for 1986 to 1994, and used Medicaid status as a proxy for low SES. The adjusted risk of death was 3.65 times higher (95% confidence interval [CI]: 3.03 to 4.40) for Medicaid patients than for those not receiving Medicaid. The percent predicted FEV(1) of surviving Medicaid patients was less by 9.1% (95% CI: 6.9 to 11.2). Medicaid patients were 2.19 times more likely to be below the 5th percentile for weight (95% CI: 1.91 to 2.51) and 2.22 times more likely to be below the 5th percentile for height (95% CI: 1.95 to 2.52) than were non-Medicaid patients. Medicaid patients were 1.60 times more likely to require treatment for a pulmonary exacerbation (95% CI: 1.29 to 1.98). There was no difference in the number of outpatient clinic visits for Medicaid and non-Medicaid patients. We conclude that low SES is associated with significantly poorer outcomes in children with CF. Barriers in access to specialty health care do not seem to explain this difference. Further study is indicated to determine what adverse environmental factors might cluster in CF patients of low SES to cause worse outcomes.

The authors conducted the largest study to date of survival in cystic fibrosis. The study cohort consisted of all patients with cystic fibrosis seen at Cystic Fibrosis Foundation-accredited care centers in the United States between 1988 and 1992 (n = 21,047), or approximately 85% of all US patients diagnosed with cystic fibrosis. Cox proportional hazards regression analysis was used to compare the age-specific mortality rates of males and females and to identify risk factors serving as potential explanatory variables for the gender-related difference in survival. Among the subjects 1-20 years of age, females were 60% more likely to die than males (relative risk = 1.6, 95% confidence interval 1.4-1.8). Outside this age range, male and female survival rates were not significantly different. The median survival for females was 25.3 years and for males was 28.4 years. Nutritional status, pulmonary function, and airway microbiology at a given age were strong predictors of mortality at subsequent ages. Nonetheless, differences between the genders in these parameters, as well as pancreatic insufficiency, age at diagnosis, mode of presentation, and race, could not account for the poorer survival among females. Even after adjustment for all these potential risk factors, females in the age range 1-20 years remained at greater risk for death (relative risk = 1.6, 95% confidence interval 1.2-2.1). The authors concluded that in 1- to 20-year-old individuals with cystic fibrosis, survival in females was poorer than in males. This "gender gap" was not explained by a wide variety of potential risk factors.

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