Comparison of FEV1 reference equations for evaluating a cystic fibrosis therapeutic intervention

Genetic Modifying Factors of Cystic Fibrosis Phenotype: A Challenge for Modern Medicine

Cystic fibrosis (CF) is a monogenic autosomal recessive disease caused by cystic fibrosis transmembrane conductance regulator (CFTR) gene mutations. CF is characterized by a high phenotypic variability present even in patients with the same genotype. This is due to the intervention of modifier genes that interact with both the CFTR gene and environmental factors. The purpose of this review is to highlight the role of non-CFTR genetic factors (modifier genes) that contribute to phenotypic variability in CF. We analyzed literature data starting with candidate gene studies and continuing with extensive studies, such as genome-wide association studies (GWAS) and whole exome sequencing (WES). The results of both types of studies revealed that the number of modifier genes in CF patients is impressive. Their identification offers a new perspective on the pathophysiological mechanisms of the disease, paving the way for the understanding of other genetic disorders. In conclusion, in the future, genetic analysis, such as GWAS and WES, should be performed routinely. A challenge for future research is to integrate their results in the process of developing new classes of drugs, with a goal to improve the prognosis, increase life expectancy, and enhance quality of life among CF patients.

Epidemiologic Study of Cystic Fibrosis: 25 years of observational research

The Epidemiologic Study of Cystic Fibrosis (ESCF) was a prospective observational study of over 32,000 people with cystic fibrosis (CF) from 250 clinical care sites in North America from 1994 to 2005. Begun as a pharmacovigilance study in connection with the approval of dornase alfa in 1993, ESCF was open to all people with CF treated at any participating site in the United States or Canada. In addition to obtaining safety and effectiveness data on dornase alfa, ESCF collected encounter-based data to characterize the natural history and management of CF with a special focus on lung disease. During the study, 32,178 patients reported at least one encounter, contributing 869,136 encounters, 622,592 pulmonary function tests, 432,896 cultures, and 118,563 pulmonary exacerbations treated with intravenous antibiotics. Although ESCF data collection concluded in 2005, through a collaboration with the U.S. Cystic Fibrosis Foundation Patient Registry, additional follow-up data through 2017 was available for two-thirds of patients. This allowed for updating of CF genotype and survival information. Fifty-six peer-reviewed publications (cited over 3600 times) resulted from this study. In this manuscript we summarize the published ESCF manuscripts in thematic groups with key study findings and brief comments, and speculate on how ESCF findings will inform future data registries and patient care practices.

Understanding FEV1 for the purpose of cystic fibrosis registry comparisons: Does bias in annual review FEV1 affect between-centre comparison within the UK? An analysis of registry data

RATIONALE, AIMS, AND OBJECTIVE

We previously demonstrated that annual review %FEV₁ underestimates lung health of adults with CF compared with %FEV₁ captured during periods of clinical stability. This has implications in the comparisons against registries with encounter-based FEV₁ , such as the United States. It is uncertain whether this bias affects between-centre comparison within the United Kingdom. Previous funnel plot analyses have identified variation in annual review %FEV₁ according to centre size; hence, we investigated whether paired differences between annual review and best %FEV₁ also vary according to centre size.

METHODS

This registry analysis included 18 adult CF centres in the United Kingdom with ≥80% completeness for best FEV₁ data in 2014. Mean discrepancy between annual review and best %FEV₁ is a surrogate for the extent by which annual review %FEV₁ underestimates lung health, and was plotted against centre size. A local polynomial regression (LOESS) curve was used to explore the relationship between the two variables. An appropriate model is fitted based on the LOESS curve to determine the strength of relationship between discrepancies in %FEV₁ and centre size.

RESULTS

There is an inverted U-shaped relationship between mean discrepancies in %FEV₁ and centre size. A regression of the paired mean difference in %FEV₁ against centre size showed a significant improvement in the goodness of fit for a quadratic model (R²  = 23.8% for a quadratic model compared with 0.4% for a linear one; P = 0.048 for the quadratic term).

CONCLUSIONS

Annual review %FEV₁ underestimated lung health of adults from small and large centres in the United Kingdom to a greater extent compared with medium-sized centres. A plot of %FEV₁ against centre size (eg, funnel plot comparison) would be affected by systematic bias in annual review %FEV₁ . Therefore, annual review %FEV₁ is an unreliable metric to compare health outcomes of adult CF centres within the United Kingdom.

Disease-modifying genetic factors in cystic fibrosis

PURPOSE OF REVIEW

To compile data from the past 10 years regarding the role of modifying genes in cystic fibrosis (CF).

RECENT FINDINGS

CF is a model disease for understanding of the action of modifying genes. Although it is a monogenic (CFTR) autosomal recessive disease, CF presents with wide phenotypic variability. In CF, variability occurs with different intensity among patients by each organ, being organ-specific, resulting from the mutual interaction of environmental and genetic factors, including CFTR mutations and various other genes, most of which are associated with inflammatory processes. In individuals, using precision medicine, gene modification studies have revealed individualized responses to drugs depending on particular CFTR mutations and modifying genes, most of which are alternative ion channels.

SUMMARY

Studies of modifying genes in CF allow: understanding of clinical variability among patients with the same CFTR genotype; evaluation of precision medicine; understanding of environmental and genetic effects at the organ level; understanding the involvement of genetic variants in inflammatory responses; improvements in genetic counseling; understanding the involvement of genetic variants in inflammatory responses in lung diseases, such as asthma; and understanding the individuality of the person with the disease.

Cystic fibrosis year in review 2017

In this article, we highlight cystic fibrosis (CF) reports published in Pediatric Pulmonology during 2017. We also include articles from a variety of journals that are related or are of special interest to clinicians.

The importance of data issues when comparing cystic fibrosis registry outcomes between countries: Are annual review FEV1 in the UK only collected when subjects are well?

RATIONALE, AIMS AND OBJECTIVE

Cross-country comparisons of cystic fibrosis (CF) outcomes can potentially identify variation in care but are dependent on data quality. An important assumption is that the UK annual review FEV₁ is only collected during periods of clinical stability. If this assumption does not hold, results of FEV₁ comparisons may be biased in favour of registries with encounter-based FEV₁ . We aimed to test the assumption that CF annual reviews in the UK are only performed during periods of clinical stability.

METHOD

Prospective encounter-based data collected in Sheffield (n = 174) was used to establish whether annual review FEV₁ were always collected during periods of clinical stability and to determine the group-level discrepancy between annual review vs best FEV₁ . We then went on to quantify the group-level discrepancy between annual review and best annual FEV₁ readings within the UK registry (n = 2995) to determine if the differences observed in Sheffield also apply to the wider UK data.

RESULTS

Sheffield results showed a group-level discrepancy between best and annual review FEV₁ of -2.5% (95% CI -3.95% to -1.2%) for annual reviews performed during periods of clinical stability (n = 50). The group-level discrepancy is larger at -8.0% (95% CI -11.2% to -4.9%) among annual reviews performed during periods of clinical instability (n = 13). Therefore, the magnitude of this group-level discrepancy is a surrogate for the proportion of clinically stable annual reviews-smaller discrepancy indicates a higher proportion of clinically stable annual reviews and vice versa. The overall group-level discrepancy in the UK registry (-5.6%, 95% CI -5.9 to -5.4%) was similar to Sheffield (-6.1%, 95% CI -7.1 to -5.1%). Around 20% of the clinician reviewed, annual reviews in Sheffield were performed during periods of clinically instability.

CONCLUSIONS

Annual review FEV₁ underestimates lung health of adults with CF in the UK and may bias cross-country comparisons.