Beyond the Local Basic Panel: Full CFTR Gene Analysis Identifies Novel CF Mutation Missed on Standard Testing in an Arabic Child.

Cystic fibrosis (CF) is an autosomal recessive disease caused by different mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. It is the most common inherited disorder in the Caucasian population, with around 2000 mutations identified for the CFTR gene. The precise prevalence of CF in Arab countries remains unknown, with the prevalence of F508 del found to be a common type with other endemic mutations. We describe the case of a CF patient who was diagnosed at the age of seven years. She presented post-cardiac surgery for further evaluation for a recurrent chest infection and subtle dysmorphic features. CF genetic testing for the most common 31 mutations (CF panel) was negative, and a novel mutation was identified on CFTR gene sequencing.

Standards of care guidance for sweat testing; phase two of the ECFS quality improvement programme.

More than five decades after the introduction of the quantitative pilocarpine iontophoresis technique, surveys still highlight inconsistencies in the performance and reporting of sweat tests in Europe. The sweat test remains key for the Cystic Fibrosis (CF) diagnostic pathway for all age groups, as it reflects the basic pathophysiological defect in the sweat gland. It is also critical following newborn screening as a confirmatory diagnostic step. Despite its importance, sweat test quality is variable whether performed in the laboratory or as a point of care test. The ECFS DNWG aims to improve sweat test performance, taking into account the barriers and issues identified in the European survey; the previous step in the ECFS sweat test project. This manuscript proposes a grading of sweat test guidance from "acceptable" to "optimal", aiming to pragmatically improve quality while taking into account local situations, especially in resource-limited settings.

mRNA-based detection of rare CFTR mutations improves genetic diagnosis of cystic fibrosis in populations with high genetic heterogeneity.

Even with advent of next generation sequencing complete sequencing of large disease-associated genes and intronic regions is economically not feasible. This is the case of cystic fibrosis transmembrane conductance regulator (CFTR), the gene responsible for cystic fibrosis (CF). Yet, to confirm a CF diagnosis, proof of CFTR dysfunction needs to be obtained, namely by the identification of two disease-causing mutations. Moreover, with the advent of mutation-based therapies, genotyping is an essential tool for CF disease management. There is, however, still an unmet need to genotype CF patients by fast, comprehensive and cost-effective approaches, especially in populations with high genetic heterogeneity (and low p.F508del incidence), where CF is now emerging with new diagnosis dilemmas (Brazil, Asia, etc). Herein, we report an innovative mRNA-based approach to identify CFTR mutations in the complete coding and intronic regions. We applied this protocol to genotype individuals with a suspicion of CF and only one or no CFTR mutations identified by routine methods. It successfully detected multiple intronic mutations unlikely to be detected by CFTR exon sequencing. We conclude that this is a rapid, robust and inexpensive method to detect any CFTR coding/intronic mutation (including rare ones) that can be easily used either as primary approach or after routine DNA analysis.

A semi-blinded study comparing 2 methods of measuring nasal potential difference: Subcutaneous needle versus dermal abrasion.

BACKGROUND: According to European and US protocols, two nasal potential difference (NPD) measurement methods are considered acceptable, although they have not been formally compared: subcutaneous agar-filled needle with calomel (Ndl) and dermal abrasion with conducting cream and Ag/AgCl electrodes (Abr). We compared both in CF and healthy volunteers (HV), assessing their discriminative value and subject's preference. METHODS: Twelve classic CF and 17 HV underwent both NPD methods, performed by one operator in random order. A written questionnaire, assessing preference, was completed after each test. Tracings were coded, scored in a semi-blinded fashion and categorised as CF/non-CF. RESULTS: 110 tracings (56 Ndl/54 Abr) were collected: 42/110 scored CF and 68/110 non-CF, showing a good correlation. No significant preference for either method was reported. CONCLUSION: Both NPD methods are similar in terms of discriminative value and subject's preference, comparing classical CF and HV. For diagnosing CF, the operator's preferred NPD-method may be used.