Forced Expiratory Volume in 1 Second Variability Helps Identify Patients with Cystic Fibrosis at Risk of Greater Loss of Lung Function

OBJECTIVE

To evaluate several alternative measures of forced expiratory volume in 1 second percent predicted (FEV1 %pred) variability as potential predictors of future FEV1 %pred decline in patients with cystic fibrosis.

STUDY DESIGN

We included 13,827 patients age ≥6 years from the Epidemiologic Study of Cystic Fibrosis 1994-2002 with ≥4 FEV1 %pred measurements spanning ≥366 days in both a 2-year baseline period and a 2-year follow-up period. We predicted change from best baseline FEV1 %pred to best follow-up FEV1 %pred and change from baseline to best in the second follow-up year by using multivariable regression stratified by 4 lung-disease stages. We assessed 5 measures of variability (some as deviations from the best and some as deviations from the trend line) both alone and after controlling for demographic and clinical factors and for the slope and level of FEV1 %pred.

RESULTS

All 5 measures of FEV1 %pred variability were predictive, but the strongest predictor was median deviation from the best FEV1 %pred in the baseline period. The contribution to explanatory power (R(2)) was substantial and exceeded the total contribution of all other factors excluding the FEV1 %pred rate of decline. Adding the other variability measures provided minimal additional value.

CONCLUSIONS

Median deviation from the best FEV1 %pred is a simple metric that markedly improves prediction of FEV1 %pred decline even after the inclusion of demographic and clinical characteristics and the FEV1 %pred rate of decline. The routine calculation of this variability measure could allow clinicians to better identify patients at risk and therefore in need of increased intervention.

Genetic relatedness of Burkholderia (Pseudomonas) cepacia isolates from five cystic fibrosis centers in Michigan

Burkholderia cepacia isolates from patients with cystic fibrosis (CF) attending five CF centers were studied for relatedness by cellular fatty acid methyl esters (FAME) and by chromosomal DNA restriction analysis. Twenty-eight of 32 (87.5%) isolates tested were grouped in cluster group 1 based on their FAME profiles. DNA analysis revealed that 29 of 32 (90.6%) B. cepacia isolates from five CF centers had one closely related DNA pattern. To examine strain variation over a time period, FAME profiles and DNA patterns of isolates from serial cultures on seven patients from center D were studied. For four patients, all serial B. cepacia isolates belonged to a single FAME cluster group; for the remaining three patients, all serial isolates belonged to any two of the four cluster groups. On serial culture isolates, a single DNA pattern (pattern A) was found in 31 of 32 isolates demonstrating a close genetic relatedness. These data corroborate the observations that the majority of patients colonised with B. cepacia in a CF center harbor strains genetically closely related as determined by FAME profiles and DNA patterns.