Chest
Volume 113, Issue 2, February 1998, Pages 396-400
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Clinical Investigations: BAC, UIP, SOD
Survival in Patients With Cryptogenic Fibrosing Alveolitis: A Population-Based Cohort Study

https://doi.org/10.1378/chest.113.2.396Get rights and content

Study objectives

To determine the median survival of patients with cryptogenic fibrosing alveolitis, in comparison to that expected of individuals of the same age and sex from the general population. To estimate the effect of survival bias incurred by studying both incident and prevalent cases. To identify factors associated with survival.

Setting

Nine hospitals from the Trent Region of England.

Patients

Two hundred forty-four cases of cryptogenic fibrosing alveolitis: 168 patients were alive on day 1 of the study (prevalent cases), and 76 patients had newly diagnosed conditions over a prospective 18-month period of patient recruitment (incident cases).

Measurements

Age, sex, date of diagnosis, lung function at presentation, and details of treatment prescribed were extracted from hospital clinical records. Data on lifetime smoking habits were collected by postal questionnaire. Vital status was established from the general practitioner. The expected survival of each case was extracted from the English life tables.

Results

Median survival for incident cases was 2.9 years and for prevalent cases 9 years, compared to expected values of 10 and 13 years, respectively. Incident cases had significantly worse survival than prevalent cases, even after adjustment for the effects of age, sex, smoking history, lung function at presentation, and treatment (hazard ratio, 4.53 [95% confidence interval, 2.71 to 7.56]; p<0.001). Lower FVC at presentation and the use of corticosteroid treatment were both associated with worse survival.

Conclusions

The inclusion of prevalent cases leads to significant overestimation of the median survival for patients with cryptogenic fibrosing alveolitis. In newly diagnosed cases of cryptogenic fibrosing alveolitis, median survival is only 2.9 years, and expected life span is reduced by approximately 7 years.

Section snippets

Materials and Methods

The patients were identified as part of a case-control study of occupational causes of cryptogenic fibrosing alveolitis. Details of patient identification, data collection, and diagnostic criteria have been published elsewhere.6 We attempted to identify all patients with cryptogenic fibrosing alveolitis attending nine centers within the Trent Region of England at the outset of the study (the prevalent cases), and all new patients seen during an 18-month recruitment period (the incident cases),

Results

A total of 168 (105 male) prevalent cases and 76 (56 male) incident cases were identified. Open lung biopsy was performed in 31 (12.7%) cases, and the mean age of these cases was significantly lower than those who did not have this procedure (52.4 years vs 69.0 years; p<0.001). The proportion of prevalent cases who underwent open lung biopsy was higher than that for incident cases, but the opposite was true for HRCT (Table 2). Incident cases tended to be older, and were more likely to be male,

Discussion

In this study, we have shown that the median survival of newly diagnosed cases of cryptogenic fibrosing alveolitis is 2.9 years, and as such is not only substantially lower than that of prevalent cases, but also considerably worse than currently recognized.3, 4, 5

To establish our population of patients, we identified patients attending a range of secondary and tertiary referral centers within the Trent region of England, and thus believe that these cases are typical of patients presenting to

ACKNOWLEDGMENTS

The authors thank Dr. Sarah Firby (actuary) for statistical advice, the lung function technicians at the nine centers involved in this study for assisting with patient identification, and the consultant physicians who allowed us to approach their patients. We would also like to thank Nottinghamshire, Derbyshire, Leicestershire, Lincolnshire, and South Yorkshire Family Health Services Authorities for help with identification of control subjects, the General Practitioners, and the Medical

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Supported by the Medical Research Council.

revision accepted July 14, 1997.

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