Part 2 on CF Predictions

[Guest guest]

The management of cystic fibrosis (CF) has improved dramatically in the

60

 years since the early description of the disease by , (1)

when the life

 expectancy of patients was < 1 year. Currently, data from a number of

registries

 estimate the median age of survival to be [greater than or equal to]

31 years.

 (2,3) This remarkable advance has been achieved through the

establishment of

 specialized care facilities, improved pancreatic enzyme preparations,

and the

 development of effective antibiotics with which to treat pulmonary

 exacerbations. (4,5) Guidelines developed by the Cystic Fibrosis

Foundation (6)

 have contributed to the standardization of CF management. These

guidelines

 recommend that patients have at least four clinical visits per year,

that the

 measurement of lung function be performed every 6 months, and that

cultures of

 respiratory tract secretions be conducted annually.

    In assessing outcomes for CF patients, the ideal measure is

mortality

 However, relatively few patients die in the short term. Therefore,

measurements

 of pulmonary function have become surrogate outcomes in most clinical

trials,

 (7-10) as there is a strong association between lung function and

mortality

 rates. (11-13)

    The Epidemiologic Study of Cystic Fibrosis (ESCF) is a

multicenter,

 longitudinal, observational study that prospectively collects

detailed clinical,

 therapeutic, microbiological, and lung function data from a large

number of CF

 treatment sites in the United States and Canada. (14-16) Initiated in

December

 1993, the study enrolled 18,411 patients by December 31, 1995.

    The goal of this study was to identify whether differences

in outcomes,

 specifically lung health as ascertained using the surrogate marker of

 FE[V.sub.1], existed between care sites. We sought to determine

whether

 particular practice patterns at care sites were associated with

better outcomes.

    In light of data linking improved survival to the frequent

use of IV

 antibiotics, (17) an additional goal of the study was to determine

whether

 intensive treatment with IV antibiotics was associated with better

outcomes.

    MATERIALS AND METHODS

    The analysis examined ESCF data collected during the 2-year

period from 1995

 through 1996. Initiated in December 1993, the study had enrolled

18,411 patients

 by December 1995, (14) which was estimated to include > 80% of the

population of

 CF patients in the United States and approximately 10% of that in

Canada The

 194 sites included > 90% of those accredited by the US Cystic

Fibrosis

 Foundation. All Canadian and US sites were invited to participate if

they had >

 10 patients. Patients were enrolled during routine care visits.

Institutional

 review boards for each site reviewed the study. Many did not require

informed

 consent as patient anonymity was maintained. Data were collected

prospectively

 at each visit or hospitalization using study-specific case report

forms. Every

 effort was made to ensure adherence to data collection by providing

 patient-specific data to the sites for source verification. In

addition, data

 comparing the site to regional and national data were provided to

investigators

 for external validation. Data-checking programs were run by the

statistical

 coordinating center (ClinTrials Research, Inc; Lexington, KY), and

queries were

 sent to the sites in order to resolve discrepancies and outliers. The

data

 included findings for every spirometry test (designated as having

been obtained

 when " sick " or " stable " ), the results of every culture, and every

 antipseudomonal antibiotic intervention and/or hospitalization.

Routine

 therapies were recorded at each visit, including the use of airway

clearance

 techniques, oral bronchodilators, inhaled bronchodilators, oral

 corticosteroids, inhaled corticosteroids, inhaled cromolyn or

nedocromil,

 inhaled dornase alfa, nonsteroidal antiinflammatory agents, insulin

or oral

 hypoglycemic agents, nutritional supplements, pancreatic enzymes, and

oral

 antibiotics. The start and stop dates of therapy with oral

quinolones, inhaled

 antibiotics, and IV antibiotics also were recorded. All of these

variables were

 examined in the analysis. A ranking was used to evaluate the use of

antibiotics

 so that if inhaled and IV antibiotics were used simultaneously, the

patient fell

 into the IV antibiotic group.

    The three age groups (6 to 12 years, 13 to 17 years, and

[greater than or

 equal to] 18 years) at each site were ranked on the basis of the last

" stable "

 median FE[V.sub.1] percent predicted value. (18) The upper and lower

quartiles

 of these groups were compared. The patients in the upper and lower

quartiles of

 each age group were pooled (Table 1) and stratified by FE[V.sub.1]

for the

 comparison of practices (Table 2), outcomes (Table 3), and

interventions (Tables

 4 and 5). The definitions of severity used the CF Foundation

categories of < 40%

 predicted of FE[V.sub.1] values for severe disease and 40 to 69%

predicted for

 moderate disease, with a modification of 70 to 99% predicted for mild

disease

 and [greater than or equal to] 100% predicted for normal. This

definition is

 consistent with the CF groupings, the population of which was

distributed so

 that the severity groups had sufficient numbers for analysis. If

there were < 10

 patients in a specific age group at an individual site, the site was

excluded

 from the evaluation of that age group. To be included in this

analysis, each

 center had to have at least 50 patients who had made at least one

visit during

 the 2-year period and had at least one spirometry test value.

Becki

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