Mild cystic fibrosis in patients with the rare P5L CFTR mutation

Identifying children with Cystic Fibrosis in population-scale routinely collected data in Wales: A Retrospective Review

INTRODUCTION

The challenges in identifying a cohort of people with a rare condition can be addressed by routinely collected, population-scale electronic health record (EHR) data, which provide large volumes of data at a national level. This paper describes the challenges of accurately identifying a cohort of children with Cystic Fibrosis (CF) using EHR and their validation against the UK CF Registry.

OBJECTIVES

To establish a proof of principle and provide insight into the merits of linked data in CF research; to identify the benefits of access to multiple data sources, in particular the UK CF Registry data, and to demonstrate the opportunity it represents as a resource for future CF research.

METHODS

Three EHR data sources were used to identify children with CF born in Wales between 1st January 1998 and 31st August 2015 within the Secure Anonymised Information Linkage (SAIL) Databank. The UK CF Registry was later acquired by SAIL and linked to the EHR cohort to validate the cases and explore the reasons for misclassifications.

RESULTS

We identified 352 children with CF in the three EHR data sources. This was greater than expected based on historical incidence rates in Wales. Subsequent validation using the UK CF Registry found that 257 (73%) of these were true cases. Approximately 98.7% (156/158) of individuals identified as CF cases in all three EHR data sources were confirmed as true cases; but this was only the case for 19.8% (20/101) of all those identified in just a single data source.

CONCLUSION

Identifying health conditions in EHR data can be challenging, so data quality assurance and validation is important or the merit of the research is undermined. This retrospective review identifies some of the challenges in identifying CF cases and demonstrates the benefits of linking cases across multiple data sources to improve quality.

Should isolated Pseudo-Bartter syndrome be considered a CFTR-related disorder of infancy?

BACKGROUND

Infants that are negative to cystic fibrosis (CF) newborn screening (NBS) programs, or in countries without NBS, may present with metabolic alkalosis and severe salt depletion, a well-known clinical manifestation of CF termed Pseudo-Bartter syndrome (PBS). Here, we report the cases of three CF-negative children, who carry rare mutations in the CF transmembrane conductance regulator (CFTR) gene, and, for whom, PBS was the only manifestation of CFTR protein dysfunction. There is no diagnostic label for these cases.

METHODS

Medical records of patients followed at our Cystic Fibrosis Centre were revised and data were collected for all patients who presented with an isolated PBS. The syndrome was defined as an episode of dehydration with low levels of serum sodium (<134mmol/L), potassium ( <3.4mmol/L), and chloride ( <100mmol/L), with metabolic alkalosis (bicarbonatemia >27mmol/L) in the absence of renal tubulopathy.

RESULTS

Three out of 73 (4%) CF infants presented with a severe metabolic alkalosis with salt depletion; two of these required admission to the intensive care unit. Two infants had a negative NBS, and one was identified as a CF carrier. Sweat test was repeatedly in the negative/borderline ranges for all patients. Less than two CF causing mutations were identified (F508del/R1070W, F508del; L467F/P5L, R1066H/P5L). During a mean follow-up of 9 years, the children had no other CF manifestations.

CONCLUSION

We suggest that PBS as the sole manifestation of CFTR dysfunction might be considered a CFTR-related disorder of infancy.

Cystic Fibrosis and the Nervous System

Cystic fibrosis (CF) is a life-shortening autosomal recessive disorder caused by mutations in the gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR). CFTR is an anion channel that conducts bicarbonate and chloride across cell membranes. Although defective anion transport across epithelial cells is accepted as the basic defect in CF, many of the features observed in people with CF and organs affected by CF are modulated by the nervous system. This is of interest because CFTR expression has been reported in both the peripheral and central nervous systems, and it is well known that the transport of anions, such as chloride, greatly modulates neuronal excitability. Thus it is predicted that in CF, lack of CFTR in the nervous system affects neuronal function. Consistent with this prediction, several nervous system abnormalities and nervous system disorders have been described in people with CF and in animal models of CF. The goal of this special feature article is to highlight the expression and function of CFTR in the nervous system. Special emphasis is placed on nervous system abnormalities described in people with CF and in animal models of CF. Finally, features of CF that may be modulated by or attributed to faulty nervous system function are discussed.